Washing appliance with a control device and method for operating said washing appliance

Abstract

The invention relates a washing appliance comprising a container apt to receive articles to be washed, a first pump assembly equipped with a first three-phase electric motor (101) having three terminal leads (U1, V1, W1), a second pump assembly equipped with a second three-phase electric motor (102) having three terminal leads (U2, V2, W2), a controllable power converter (200) having three outputs (U, V, W) for providing electric power to the electric motors (101, 102) and a control device (204) to control the controllable power converter (200). There is provided a switching device (300) interposed between the controllable power converter (200) and the electric motors (101, 102), wherein the switching device (300) is configured to be disposed in a first position to operate the first electric motor (101) and a second position to operate the second electric motor (102).

Description

[0001] WASHING APPLIANCE AND CONTROL SYSTEM THEREOF

[0002] FIELD OF THE INVENTION

[0003] The present invention concerns the field of washing appliances for washing articles provided with a plurality of pump assemblies.

[0004] In particular, the present invention refers to a washing appliance provided with a wash pump assembly and a drain pump assembly each operated by a respective wash pump motor and drain pump motor.

[0005] BACKGROUND ART

[0006] Washing appliances for washing articles, such as dishwashers or laundry washing machines, typically include one or more pump assemblies.

[0007] For example, a dishwasher typically comprises a wash pump assembly and a drain pump assembly wherein the wash pump assembly is configured to circulate wash liquid inside a tub to wash the articles / tableware and the drain pump assembly is configured to drain waste liquid outside the appliance during and / or after use. Analogously, a laundry washing machines typically comprises a wash pump assembly and a drain pump assembly wherein the wash pump assembly is configured to circulate washing liquid inside a drum to wash the laundry and the drain pump assembly is configured to drain waste liquid outside the appliance during and / or after use.

[0008] As known, a pump assembly comprises a pump having an inlet and an outlet for liquid and the pump has the aim of increasing the pressure and flow of the liquid from the inlet towards the outlet. The pump assembly is equipped with an electric motor, for example a single-phase electric motor or a three-phase electric motor, adapted to be powered / fed between its electrical terminals causing activation of the pump, for example rotation of an impeller inside the pump.

[0009] Such pump assemblies are generally disposed in the sump of the appliance and are generally supplied with a system voltage from the domestic (mains) system.

[0010] US8461783B2 discloses a dishwasher provided with a common control device by means of which two electric motors for respective pumps are controlled. Electric motors are implemented as permanent magnet excited synchronous motors and are connected to a 3-phase voltage system. The common control device is preferably embodied to provide the supply voltage to a first of the two motors or to the other motor when required, for driving the respective pump. The control device comprises a connection device formed by a switch arrangement actuatable in parallel. The electric motors can be connected to the 3-phase voltage system such that the first motor and the second motor can be alternately operated from the 3- phase voltage system.

[0011] US10206551B2 also discloses a dishwasher provided with two electric motors for respective pump assemblies, for example a wash pump assembly and a drain pump assembly. There is provided a relay configured to be adjusted between at least a first position associated with a first circuit of the first motor and a second position associated with a second circuit of the second motor. A control device is configured to identify the position of the relay. Further, operations are preferably performed to determine whether the relay is in the first position or in the second position based on test signals provided to the relay. In particular, said operations comprises providing a test signal to the relay and detecting an output signal that is based on the test signal, wherein the output signal is associated with the second circuit. It is determined that the relay is in the first position when the output signal corresponds to a first reference signal indicative of the relay being in the first position and it is determined that the relay is in the second position when the output signal corresponds to a second reference signal indicative of the relay being in the second position.

[0012] It is important to identify the current position of the relay, and hence which motor is connected to a power source before applying such power.

[0013] In preferred embodiments, it is convenient to choose electric motors having different sizes for manufacture flexibility and cost reasons. For example, the drain electric motor may be selected to have a lower rated power than the wash electric motor, so that the power required to operate the drain electric motor may be lower than the power required to operate the wash electric motor.

[0014] To avoid damage to the dishwasher and / or to comply with safety standards, it is important to identify which assembly is connected to the power source and then apply the specific power requested by the motor currently connected.

[0015] It is an object of the invention to propose a more efficient and safe control management system relating two pump assemblies in a washing appliance.

[0016] DISCLOSURE OF INVENTION Applicant has found that by providing a washing appliance comprising a first pump assembly equipped with a first three-phase electric motor having three terminal leads and a second pump assembly equipped with a second three-phase electric motor having three terminal leads, a controllable power converter, a control device to control said controllable power converter, a switching device interposed between said controllable power converter and said electric motors and configured to be disposed in a first position to operate said first electric motor and a second position to operate said second electric motor, a first feedback circuit electrically connected to a first terminal lead of said first electric motor and to said control device, a second feedback circuit electrically connected to a second terminal lead of said first electric motor and to said control device, it is possible to reach the mentioned objects.

[0017] In an aspect thereof the present invention relates, therefore, to a washing appliance comprising:

[0018] - a container apt to receive articles to be washed;

[0019] - a first pump assembly equipped with a first three-phase electric motor having three terminal leads;

[0020] - a second pump assembly equipped with a second three-phase electric motor having three terminal leads;

[0021] - a controllable power converter having three outputs for providing electric power to said electric motors;

[0022] - a control device to control said controllable power converter;

[0023] - a switching device interposed between said controllable power converter and said electric motors, said switching device being configured to be disposed in a first position to operate said first electric motor and a second position to operate said second electric motor, wherein first and second outputs of said converter are connected to said switching device, first and second terminal leads of said first electric motor are connected to said switching device and first and second terminal leads of said second electric motor are connected to said switching device, the third output of said converter being directly connected to both said first terminal lead of said first electric motor and said first terminal lead of said second electric motor, said switching device comprising:

[0024] - a first contact displaceable in a first position to connect said first output of said converter to said first terminal lead of said first electric motor when said switching device is in said first position and in a second position to connect said first output of said converter to said first terminal lead of said second electric motor when said switching device is in said second position;

[0025] - a second contact displaceable in a first position to connect said second output of said converter to said second terminal lead of said first electric motor when said switching device is in said first position and in a second position to connect said second output of said converter to said second terminal lead of said second electric motor when said switching device is in said second position;

[0026] - at least one actuator acting on said first contact for displacing it in said first position or said second position and acting on said second contact for displacing it in said first position or said second position;

[0027] - said control device further comprising at least one switch drive output to activate or de-activate said at least one actuator for driving said switching device in said first position or said second position;

[0028] - a first feedback circuit electrically connected to a first terminal lead of said first electric motor and to said control device;

[0029] - a second feedback circuit electrically connected to a second terminal lead of said first electric motor and to said control device;

[0030] - said control device further comprising a first sense input for sensing a first electrical parameter coming from said first feedback circuit and a second sense input for sensing a second electrical parameter coming from said second feedback circuit.

[0031] Advantageously, in the appliance according to the invention, it is possible to evaluate if the switching device is correctly positioned in the requested first or second position and hence the actual electric motor may be powered with the specific power required by the specific electric motor through the converter. Therefore, advantageously, one of the electric motors may be selected to have a lower rated power than the other electric motor and then be powered with the specific power, thereby avoiding damage to the same electric motor.

[0032] In a preferred embodiment, the appliance further comprises at least one feedback switching circuit electrically connected to said actuator and to said control device and said control device further comprising at least one switch control input for sensing a switching electrical parameter coming from said at least one feedback switching circuit. Advantageously, the feedback switching circuit allows to evaluate if the switching device is operating correctly.

[0033] According to a preferred embodiment, the actuator comprises a coil apt to be energized to switch the switching device from the first position to the second position and apt to be de-energized to switch said switching device from the second position to the first position and said at least one feedback switching circuit is electrically connected to the coil and the control device.

[0034] Preferably, the controllable power converter is as a three-phase voltage system, more preferably a three-phase inverter comprising six inverter switches arranged in a three-phase bridge with three legs each having a pair of switches.

[0035] Preferably, the first and / or the three-phase electric motor is a three-phase brushless AC electric motor or a three-phase brushless DC electric motor.

[0036] In a preferred embodiment, the switching electrical parameter and / or the first electrical parameter and / or the second electrical parameter electrical parameter is an electric voltage.

[0037] Preferably, the first feedback circuit is configured to provide the first electrical parameter as an electric voltage or a current and / or the second feedback circuit is configured to provide the second electrical parameter as an electric voltage or a current, wherein the first feedback circuit and / or the second feedback circuit is preferably a voltage divider, more preferably a resistive partitor.

[0038] According to a preferred embodiment, the appliance comprises a user interface panel through which a user can select various operational features and / or monitor the functioning of the appliance, preferably a display providing operational feedback to a user or showing alarm messages. The control device preferably communicates with the user interface panel.

[0039] In a preferred embodiment, the control device shares information and / or communicates with external devices, such as an access point like a home gateway or a smartphone.

[0040] In a further aspect the present invention relates to a method for operating a washing appliance as described above, wherein said method comprises the steps of: a) activate or de-activate said at least one actuator, through said switch drive output, for positioning said switching device in said first position wherein said first and second contacts are in said first position or positioning said switching device in said second position wherein said first and second contacts are in said second position; b) performing a method for evaluating if said switching device is correctly positioned in said first position or in said second position comprising the steps of: bl) performing a first test procedure comprising the steps of:

[0041] - applying a first test signal to said switching device by driving said converter to provide electric power to said first output of said converter and not to provide electric power to said second and third outputs of said converter;

[0042] - sensing said first electrical parameter;

[0043] - determining that said first contact is correctly in said first position if said first electrical parameter substantially matches an expected reference parameter indicative of said first terminal lead of said first electric motor being powered or determining that said first contact is correctly in said second position if said first electrical parameter substantially matches an expected reference parameter indicative of said first terminal lead of said first electric motor being not powered; b2) performing a second test procedure comprising the steps of:

[0044] - applying a second test signal to said switching device by driving said converter to driving said converter to provide electric power to said second output of said converter and not to provide electric power to said first and third outputs of said converter;

[0045] - sensing said second electrical parameter;

[0046] - determining that said second contact is correctly in said first position if said second electrical parameter substantially matches an expected reference parameter indicative of said second terminal lead of said first electric motor being powered or determining that said second contact is correctly in said second position if said second electrical parameter substantially matches an expected reference parameter indicative of said second terminal lead of said first electric motor being not powered; c) if the result of said first and second test procedures is that said first contact and said second contact are correctly in said first position, operating said first electric motor through said converter, or if the result of said first and second test procedures is that said first contact and said second contact are correctly in said second position, operating said second electric motor through said converter.

[0047] Advantageously, the method of invention allows to evaluate if the switching device is correctly positioned in the requested first or second position and hence the actual electric motor may be powered with the specific power required by the specific electric motor through the converter. Therefore, advantageously, one of the electric motors may be selected to have a lower rated power than the other electric motor and then be powered with the specific power, thereby avoiding damage to the same electric motor.

[0048] In a preferred embodiment, after steps bl) and b2) the method comprises the step of: d) if the result of said first test procedure is that said first contact or said second contact is not correctly in said first position or if the result of said second test procedure is that said first contact or said second contact is not correctly in said second position, performing at least one of the following:

[0049] - preventing operating said first electric motor or said second electric motor;

[0050] - generating an alarm message.

[0051] Advantageously, if the switching device is not correctly positioned in the requested first or second position proper safety measures are implemented, thereby avoiding damage to the same electric motor.

[0052] Preferably, after step a) and before step b) the method comprises the following steps: e) performing a third test procedure for verifying that the wiring of said electric motors is correct and that said switching device is working correctly, said third test procedure comprising the steps of:

[0053] - applying a third test signal to said switching device by driving said converter to provide electric power to said third output of said converter and not to provide electric power to said first and second outputs of said converter;

[0054] - sensing said first electrical parameter and said second electrical parameter;

[0055] - determining that the wiring of said electric motors is correct and that said switching device is working correctly if said first electrical parameter substantially matches an expected reference parameter indicative of both said third terminal leads of said first and second electric motors being powered and if said second electrical parameter substantially matches an expected reference parameter indicative of both said third terminal leads of said first and second electric motors being powered; f) if the result of said third test procedure is that the wiring of said electric motors is correct and said switching device is working correctly, proceeding with step b). Advantageously, the third test procedure verifies that the wiring of the electric motors is correct and that the switching device is working correctly before the evaluation that the switching device is correctly positioned in the requested first or second position.

[0056] According to a preferred embodiment, after step e) the method comprises the step of: g) if the result of said third test procedure is that the wiring of said electric motors is not correct and / or said switching device is not working correctly, performing at least one of the following:

[0057] - preventing operating said first electric motor or said second electric motor;

[0058] - generating an alarm message.

[0059] Advantageously, if the wiring of the electric motors is not correct and / or the switching device is not working correctly proper safety measures are implemented, thereby avoiding damage to the same electric motor.

[0060] Preferably, when the appliance comprises at least one feedback switching circuit, after step a) and before step b) the method comprises the steps of: h) performing a switching device test for evaluating that said switching device is operating correctly, said switching device test comprising the steps of:

[0061] - sensing said switching electrical parameter;

[0062] - determining that said switching device is operating correctly if said switching electrical parameter substantially matches an expected reference parameter indicative of said actuator being activated or de-activated; i) if the result of said switching device test is that said switching device is operating correctly, proceeding with step b).

[0063] Preferably, it is determined that the said switching device is operating correctly both if the voltage at the switch control input is higher when the actuator is activated via the switch drive output and if the voltage at the switch control input is lower when the actuator is de-activated via the switch drive output.

[0064] Advantageously, the switching device test verifies that the switching device is operating correctly.

[0065] In a preferred embodiment, after step h) the method comprises the step of:

[0066] 1) if the result of said switching device test is that said switching device is operating incorrectly, performing at least one of the following:

[0067] - preventing operating said first electric motor or said second electric motor; - generating an alarm message.

[0068] Preferably, it is determined that the said switching device is operating incorrectly if the voltage at the switch control input is not higher when the actuator is activated via the switch drive output or if the voltage at the switch control input is not lower when the actuator is de-activated via the switch drive output.

[0069] Advantageously, if the switching device is operating incorrectly proper safety measures are implemented, thereby preventing damage to the electric motor.

[0070] In a preferred embodiment, when the appliance comprises at least one feedback switching circuit, after step a) and before step b) the method comprises the steps of: h) performing a switching device test for evaluating that said switching device is operating correctly, said switching device test comprising the steps of:

[0071] - sensing said switching electrical parameter;

[0072] - determining that said switching device is operating correctly if said switching electrical parameter substantially matches an expected reference parameter indicative of said actuator being activated or de-activated; i) if the result of said switching device test is that said switching device is operating correctly, then: e) performing a third test procedure for verifying that the wiring of said electric motors is correct and that said switching device is working correctly, said third test procedure comprising the steps of:

[0073] - applying a third test signal to said switching device by driving said converter to provide electric power to said third output of said converter and not to provide electric power to said first and second outputs of said converter;

[0074] - sensing said first electrical parameter and said second electrical parameter;

[0075] - determining that the wiring of said electric motors is correct and that said switching device is working correctly if said first electrical parameter substantially matches an expected reference parameter indicative of both said third terminal leads of said first and second electric motors being powered and if said second electrical parameter substantially matches an expected reference parameter indicative of both said third terminal leads of said first and second electric motors being powered; f) if the result of said third test procedure is that the wiring of said electric motors is correct and said switching device is working correctly, proceeding with step b). Advantageously, first the switching device test verifies that the switching device is operating correctly and then the third test procedure verifies that the wiring of the electric motors is correct and that the switching device is working correctly. According to a preferred embodiment, after step h) the method comprises the step of:

[0076] 1) if the result of said switching device test is that said switching device is operating incorrectly, performing at least one of the following:

[0077] - preventing operating said first electric motor or said second electric motor;

[0078] - generating an alarm message.

[0079] Advantageously, if the switching device is operating incorrectly proper safety measures are implemented, thereby preventing damage to the electric motor.

[0080] In a preferred embodiment, 1 after step e) the method comprises the step of: g) if the result of said third test procedure is that the wiring of said electric motors is not correct and / or said switching device is not working correctly, performing at least one of the following:

[0081] - preventing operating said first electric motor or said second electric motor;

[0082] - generating an alarm message.

[0083] Advantageously, if the wiring of the electric motors is not correct and / or the switching device is not working correctly proper safety measures are implemented, thereby avoiding damage to the same electric motor.

[0084] In a further aspect the present invention relates to a method for operating a washing appliance as described above, wherein said method comprises the steps of: a) performing a test procedure for verifying that the wiring of said electric motors is correct and that said switching device is working correctly, said test procedure comprising the steps of:

[0085] - applying a test signal to said switching device by driving said converter to provide electric power to said third output of said converter and not to provide electric power to said first and second outputs of said converter;

[0086] - sensing said first electrical parameter and said second electrical parameter;

[0087] - determining that the wiring of said electric motors is correct and that said switching device is working correctly if said first electrical parameter substantially matches an expected reference parameter indicative of both said third terminal leads of said first and second electric motors being powered and if said second electrical parameter substantially matches an expected reference parameter indicative of both said third terminal leads of said first and second electric motors being powered; b) if the result of said test procedure is that the wiring of said electric motors is correct and said switching device is working correctly, operating said first electric motor through said converter or operating said second electric motor through said converter.

[0088] Advantageously, the test procedure verifies that the wiring of the electric motors is correct and that the switching device is working correctly and hence the actual electric motor may be powered through the converter.

[0089] According to a preferred embodiment, after step a) the method comprises the step of: c) if the result of said test procedure is that the wiring of said electric motors is not correct and / or said switching device is not working correctly, performing at least one of the following:

[0090] - preventing operating said first electric motor or said second electric motor;

[0091] - generating an alarm message.

[0092] Advantageously, if the wiring of the electric motors is not correct and / or the switching device is not working correctly proper safety measures are implemented, thereby avoiding damage to the same electric motor.

[0093] In a further aspect the present invention relates to a method for operating a washing appliance comprising at least one feedback switching circuit as described above, wherein said method comprises the steps of: a) driving said switching device, through said switch drive output, for activating or de-activating said actuator to drive said switching device from said first position to said second position or from said second position to said first position; b) performing a switching device test for evaluating that said switching device is operating correctly, said switching device test comprising the steps of:

[0094] - sensing said switching electrical parameter;

[0095] - determining that said switching device is operating correctly if said switching electrical parameter substantially matches an expected reference parameter indicative of said actuator being activated or de-activated; c) if the result of said switching device test is that said switching device is operating correctly, performing one of the following step dl) or d2): dl) operating said first electric motor through said converter or operating said second electric motor through said converter; d2) performing a method for evaluating if said switching device is correctly positioned in said first position or in said second position by evaluating said first electrical parameter at said first sense input and said second electrical parameter at said second sense input and if the result of said method is that said first contact and said second contact are correctly in said first position, operating said first electric motor through said converter, or if the result of said method is that said first contact and said second contact are correctly in said second position, operating said second electric motor through said converter.

[0096] Preferably, it is determined that the said switching device is operating correctly both if the voltage at the switch control input is higher when the actuator is activated via the switch drive output and if the voltage at the switch control input is lower when the actuator is de-activated via the switch drive output.

[0097] Advantageously, the switching device test first verifies that the switching device is operating correctly and then either the actual electric motor may be powered through the converter or a further method is performed to evaluate if the switching device is correctly positioned in the requested first or second position and hence the actual electric motor may be powered with the specific power required by the specific electric motor through the converter. Therefore, advantageously, one of the electric motors may be selected to have a lower rated power than the other electric motor and then be powered with the specific power, thereby avoiding damage to the same electric motor.

[0098] In a preferred embodiment, after step b) the method comprises the step of: e) if the result of said switching device test is that said switching device is operating incorrectly, performing at least one of the following:

[0099] - preventing operating said first electric motor or said second electric motor;

[0100] - generating an alarm message.

[0101] Preferably, it is determined that the said switching device is operating incorrectly if the voltage at the switch control input is not higher when the actuator is activated via the switch drive output or if the voltage at the switch control input is not lower when the actuator is de-activated via the switch drive output.

[0102] Advantageously, if the switching device is operating incorrectly proper safety measures are implemented, thereby preventing damage to the electric motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0103] Further characteristics and advantages of the present invention will be highlighted in greater detail in the following detailed description of preferred embodiments of the invention, provided with reference to the enclosed drawings. In the drawings, corresponding characteristics and / or components are identified by the same reference numbers. In such drawings:

[0104] - Figure 1 shows in a schematic form a circuit arrangement according to a preferred exemplary embodiment of the present invention in a first operative condition;

[0105] - Figure 1 A shows in a schematic form a circuit arrangement according to a further preferred exemplary embodiment of Figure 1 ;

[0106] - Figure 2 shows the circuit arrangement of Figure 1 in a second operative condition;

[0107] - Figures 3A and 3B show example phase diagrams relating to execution of the relay test procedure;

[0108] - Figure 4 depicts a first test procedure according to a preferred exemplary embodiment of the present invention;

[0109] - Figure 5 shows the circuit arrangement of Figure 1 during implementation of the first test procedure;

[0110] - Figure 6 shows the circuit arrangement of Figure 2 during the execution of the first test procedure;

[0111] - Figures 7 A and 7B show example phase diagrams relating to execution of the first test procedure;

[0112] - Figure 8 depicts a second test procedure according to a preferred exemplary embodiment of the present invention;

[0113] - Figure 9 shows the circuit arrangement of Figure 1 during implementation of the second test procedure;

[0114] - Figure 10 shows the circuit arrangement of Figure 2 during the execution of the second test procedure;

[0115] - Figures 11 A and 1 IB show example phase diagrams relating to execution of the second test procedure;

[0116] - Figure 12 depicts a method according to a preferred exemplary embodiment of the present invention;

[0117] - Figure 13 depicts a third test procedure according to a preferred exemplary embodiment of the present invention; - Figure 14 shows the circuit arrangement of Figure 1 during implementation of the third test procedure;

[0118] - Figure 15 shows the circuit arrangement of Figure 2 during the execution of the third test procedure;

[0119] - Figures 16A and 16B show example phase diagrams relating to execution of the third test procedure;

[0120] - Figure 17 depicts a method according to a preferred exemplary embodiment of the present invention;

[0121] - Figures 18 to 20 depict further preferred exemplary embodiments of the method of Figure 12.

[0122] DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

[0123] The present invention has proved to be particularly advantageous when applied to dishwashers provided with a wash pump assembly and a drain pump assembly, as described in detail below.

[0124] It should in any case be underlined that the present invention is not limited to dishwashers. The present invention can be conveniently applied to any washing appliance for washing articles provided with at least two pump assemblies, for example a laundry washing machine.

[0125] According to an aspect of the invention, two pump assemblies of an appliance are operated using a single circuit, as shown in the circuit arrangements of Figures 1 and 1A.

[0126] A pump assembly, as known, has the aim of increasing the pressure and flow of a liquid from an inlet to an outlet of the pump, for example through a rotatable impeller arranged inside the pump. The pump assembly is equipped with an electric motor, for example a single-phase electric motor or a three-phase electric motor, adapted to be powered / fed between its electrical terminals causing activation of the pump, for example through rotation of the impeller.

[0127] In preferred embodiments, there are used variable speed electric motors to control the liquid flow. As in the preferred embodiments illustrated and described herein, preferably three-phase electric motors 101, 102 are used, more preferably three- phase brushless AC electric motors 101, 102, or three-phase BLAC electric motors 101, 102. The electric motors 101, 102 are implemented as permanent magnet excited synchronous motors. The permanent magnet excited synchronous motor belongs to the category of polyphase machines and has a symmetrical 3 -phase stator winding which is supplied with 3-phase AC voltage at proper terminal leads, conventionally indicated as U, V, W.

[0128] In further preferred embodiment, three-phase brushless DC electric motors can be used, or three-phase BLDC electric motors.

[0129] According to preferred embodiments of the present invention, as illustrated in Figures 1 and 1A, a dishwasher (not shown) having a wash chamber, or tub, for receiving articles / tableware to be washed is preferably provided with a drain pump assembly having a respective drain electric motor 101 and a wash pump assembly having a respective wash electric motor 102.

[0130] The drain pump assembly is configured to drain waste liquid outside the dishwasher during and / or after use and the wash pump assembly is configured to circulate the wash liquid inside the tub to wash the articles.

[0131] The electric motors 101, 102 preferably are three-phase BLAC electric motors and each motor 101, 102 identifies respective terminal leads Ul, VI, W1 and U2, V2, W2.

[0132] In a preferred embodiment, the two electric motors 101, 102 can be chosen to have different sizes.

[0133] For example, in a preferred embodiment, the drain electric motor 101 is selected to have a lower rated power than the wash electric motor 102, so that the power required to operate the drain electric motor 101 is lower than the power required to operate the wash electric motor 102. For example, the drain electric motor 101 has a rated power of 20W and the wash electric motor 102 has a rated power of 80W. Advantageously, a minor cost electric motor may be used for the drain electric motor compared to the wash electric motor.

[0134] A three-phase controllable power converter 200 is used for providing three separate AC waveforms to the electric motors 101, 102 from a DC input voltage line HVDC (High Voltage Direct Current), for example HVDC=325Volt DC.

[0135] The three-phase converter 200 identifies respective three outputs U, V, W, or phases, connectable to respective terminal leads Ul, VI, W1 of the drain electric motor 101 or to respective terminal leads U2, V2, W2 of the wash electric motor 102, as described in detail later.

[0136] The three-phase controllable power converter 200 is thus preferably configured as a three-phase voltage system having three outputs U, V, W for driving the three- phase electric motors 101, 102.

[0137] A control device 204, or controller 204, is configured to control the converter 200. Throughout the description, operations relating to disclosed processes and / or methods are preferably performed by the control device 204.

[0138] Generally, the dishwasher is equipped with one or more control devices for performing operations. The controller may comprise a microprocessor and memory operable to execute programming instructions or micro-control code associated with a wash cycle. The memory may be a separate component from the processor or may be incorporated into the processor. In addition, the control device preferably communicates with a user interface panel through which a user can select various operational features and / or monitor the functioning of the dishwasher, for example a display providing operational feedback to a user or showing alarm messages.

[0139] The control device / s may then preferably share information and / or communicate with external devices, such as an access point like a home gateway or a smartphone.

[0140] As shown in Figures 1 and 1A, the converter 200 preferably comprises a three- phase inverter 202.

[0141] The inverter 202 preferably comprises six inverter switches 2a, 2b, 4a, 4b, 6a, 6b arranged in a three-phase bridge with three legs each having a pair of switches 2a- 2b, 4a-4b, 6a-6b. Preferably, inverter switches 2a, 2b, 4a, 4b, 6a, 6b comprise insulated-gate bipolar transistors 2a, 2b, 4a, 4b, 6a, 6b, or IGBTs (also known as 3-phase IGBT inverter bridge). The inverter switches in one alternative embodiment may also be designed for example as Metal-Oxide-Semiconductor Field- Effect Transistors (MOSFETs).

[0142] The inverter 202 can consist of discrete components or an integrated chip. Inverter switches are hereinafter simply indicated with the term transistors.

[0143] Each pair 2a-2b, 4a-4b, 6a-6b of transistors are connected in series and an intermediate point between them defines a respective output U, V, W of the converter 200.

[0144] Hereinafter, we conventionally refer to: first output V of the converter 200; second output W of the converter 200, third output U of the converter 200; first terminal lead VI of the first electric motor 101 ; second terminal lead W1 of the first electric motor 101; third terminal lead U1 of the first electric motor 101; first terminal lead V2 of the second electric motor 102; second terminal lead W2 of the second electric motor 102; third terminal lead U2 of the second electric motor 102.

[0145] Furthermore, the inverter 202 identifies a so called “high-side” which is defined by the three upper transistors 2a, 4a, 6a connected to the DC input voltage line HVDC and a so called “low-side” which is defined by the three lower transistors 2b, 4b, 6b connected to ground GND, preferably via respective shunt resistors I la, 11b, 11c.

[0146] The controller 204 opportunely drives the transistors 2a, 2b, 4a, 4b, 6a, 6b of the inverter 202 through respective control connections 8.1, 8.2, 8.3, 9.1, 9.2, 9.3. Three of said control connections 8.1, 8.2, 8.3 control the high-side of the inverter 202 and three of said control connections 9.1, 9.2, 9.3 control the low-side of the inverter 202.

[0147] In particular: the first control connection 8.1 drives the high-side first transistor 2a, the second control connection 8.2 drives the high- side second transistor 4a, the third control connection 8.3 drives the high- side third transistor 6a, the first control connection 9.1 drives the low-side first transistor 2b, the second control connection 9.2 drives the low-side second transistor 4b, the third control connection 9.3 drives the low- side third transistor 6b.

[0148] The high-side control connections 8.1, 8.2, 8.3 are only explicitly shown in Figure 1, while in other figures they are identified globally by reference number 8.

[0149] Similarly, the low-side control connections 9.1, 9.2, 9.3 are only explicitly shown in Figure 1 , while in other figures they are identified globally by reference number 9.

[0150] Three inputs 10.1, 10.2 and 10.3 of the controller 204 are preferably connected to the three legs of the three-phase bridge of the inverter 202, more preferably connected to terminals of the resistors I la, 11b, 11c. The three inputs 10.1, 10.2 and 10.3 of the controller 204 are therefore configured to detect the current flowing through each leg of the three-phase bridge of the inverter 202.

[0151] According to an aspect of the invention, a switching device 300 is interposed between the converter 200 and the electric motors 101, 102.

[0152] The switching device 300 acts to selectively operate the first electric motor 101 or the second electric motor 102 with electric power provided by the converter 200. The switching device 300 is configured to be disposed in a first position (Figures 1 and 1A) to operate the first electric motor 101 (drain electric motor 101) and a second position (Figure 2) to operate the second electric motor 102 (wash electric motor 102).

[0153] Preferably, the switching device 300 is interposed between two outputs V, W of the converter 200 and respective two terminal leads VI , W 1 , V2, W2 of the electric motors 101, 102 while the third output U of the converter 200 is directly electrically connected to both third terminal leads Ul, U2 of the electric motors 101, 102.

[0154] Preferably, there is provided a first connector 102 A for the electrical connection of terminal leads Ul , VI , W1 of the first electric motor 101 to the switching device 300 and to the third output U of the converter 200.

[0155] Analogously, there is provided a second connector 102B for the electrical connection of terminal leads U2, V2, W2 of the second electric motor 102 to the switching device 300 and to the third output U of the converter 200.

[0156] According to a preferred embodiment of the invention, the switching device 300 is an electrically operated switch, hereinafter also simply indicated as “relay 300”, with two input terminals connected to the outputs V, W of the converter 200 and four output terminals connected to the terminal leads VI, Wl, V2, W2 of the electric motors 101, 102.

[0157] The relay 300 comprises two contacts A, B which are movable in a first position (Figure 1) and in a second position (Figure 2) to dispose the relay 300 in its first or second position. The first position of the two contacts A, B eventually corresponds to the first position of the relay 300 and the second position of the two contacts A, B eventually corresponds to the second position of the relay 300.

[0158] The two contacts A, B preferably move together (simultaneously) between the first position and the second position, or vice versa.

[0159] An actuator 302 acts on said first contact A for displacing it in the first position or the second position and / or acts on the second contact B for displacing it in the first position or the second position.

[0160] The relay 300 is preferably an electromagnetic relay 300 and the actuator 302 comprises a coil 302 (actuator 302) that can be energized for moving the two contacts A, B. The coil 302 is preferably powered by an operating low voltage Vo, for example Vo=12Volt DC.

[0161] Preferably, when the actuator 302 is de-actuated, i.e the coil 302 is de-energized, the first contact A is in its first position and the first output V of the converter 200 is connected to the first terminal lead VI of the first electric motor 101 and the second contact B is in its first position and the second output W of the converter 200 is connected to the second terminal lead W1 of the first electric motor 101, i.e. contacts A, B and the relay 300 are in the first position shown in Figure 1.

[0162] When the actuator 302 is actuated, i.e the coil 302 is energized, , the first contact A is in its second position and the first output V of the converter 200 is connected to the first terminal lead V2 of the second electric motor 102 and the second contact B is in its second position and the second output W of the converter 200 is connected to the second terminal lead W2 of the second electric motor 102, i.e. contacts A, B and the relay 300 are in the second position shown in Figure 2.

[0163] The relay 300 is thus preferably configured as a monostable relay, wherein when the coil 302 is energized the relay 300 operates and assumes the second position and after the coil 302 is de-energized the switching operation reverses, and the relay 300 is automatically moved to the first position, preferably held in place in the first position by a spring .

[0164] Energization or de-energization of the coil 302, and hence determination of the positions of the contacts A and B, is preferably established by the controller 204 through a coil drive output 12, or switch drive output 12.

[0165] A coil drive circuit 301 is preferably interposed between the coil 302 and the switch drive output 12 the controller 204. The coil drive circuit 301 preferably comprises an electronic switch 304 electrically connected in series to the coil 302. The coil drive output 12 of the controller 204 drives the electronic switch 304.

[0166] When the coil drive output 12 switches on (closes) the electronic switch 304 the coil 302 is energized, and when the coil drive output 12 switches off (opens) the electronic switch 304 the coil 302 is de-energized. The electronic switch 304 is preferably switched on with a higher voltage signal at the coil drive output 12 and the electronic switch 304 is preferably switched off with a lower voltage signal at the coil drive output 12.

[0167] The electronic switch 304 is implemented preferably in a semiconductor technology. In the present case the electronic switch is preferably a bipolar NPN transistor. The electronic switch in one alternative embodiment may also be designed differently, for example as a field effect transistor (FET).

[0168] According to a preferred embodiment, the relay 300 is configured so that the contacts A, B are held in the first position when the coil 302 is de-energized, i.e. the relay 300 may be of the type known as normally closed contact relay (NC contact relay) and hence the first electric motor 101, i.e. the drain electric motor 101, is connected to the converter 200. The contacts A, B are preferably held in place by a spring when the coil 302 is de-energized.

[0169] This configuration is particularly advantageous when the coil 302 is de-energized due to a failure of the coil 302 and / or of the electronic switch 304. In such a case, in fact, the first electric motor 101 is connected to the converter 200 and the operation of the drain electric motor 101 is guaranteed. This advantageously satisfies the safety requirement for a dishwasher where it is preferable for the drain pump assembly to continue to operate in the event of failure so that water can be drained from the machine and flooding avoided.

[0170] According to an aspect of the invention and as illustrated in Figure 1 , a feedback switching circuit 310 is preferably provided between the relay 300 and the controller 204.

[0171] It should be noted that the preferred alternative embodiment of the circuit arrangement shown in Figure 1A differs from the circuit arrangement shown in Figure 1 in that said feedback switching circuit is omitted. Such an alternative circuit arrangement may be used in connection with procedures / methods described later in which the feedback switching circuit is not required.

[0172] Preferably, the feedback switching circuit 310 is electrically connected, at one hand, to the coil 32 of the relay and, on the other hand, to the controller 204, in particular to a switch control input 14 of the controller 204, or coil control input 14.

[0173] The coil control input 14 senses a switching electrical parameter coming from the feedback switching circuit 310.

[0174] Preferably, the feedback switching circuit 310 comprises a shunt resistor 306 disposed between the electronic switch 304 and the ground GND.

[0175] The coil control input 14 hence preferably senses the voltage generated by the shunt resistor 306 when the current flows therethrough, wherein said current is also the current flowing through the coil 302.

[0176] The coil control input 14 is therefore configured to detect if a current is flowing through the coil 302, i.e. to detect if the coil 302 is energized or de-energized.

[0177] According to an aspect of the invention, the controller 204 is configured to perform a relay test 4000 to detect that the relay 300 is operating correctly.

[0178] The relay test 4000 is preferably carried out in the circuit arrangement of Figure 1 which is equipped with the feedback switching circuit 310.

[0179] In particular, the controller 204 determines the correct operation of the coil 302, namely the correct energization of the coil 302, via the coil control input 14 in response to a drive signal at the coil drive output 12 to switch on (close) the electronic switch 304.

[0180] If the coil 302 is energized, i.e. the coil drive output 12 switches on (closes) the electronic switch 304 so that the current flows through the coil 302, the contacts A, B are moved to the second position, as said above, and the voltage at the coil control input 14 is expected to be higher being the current flowing through the coil 302 and the shunt resistor 306.

[0181] Conversely, if the coil 302 is de-energized, i.e. the coil drive output 12 switches off (opens) the electronic switch 304 so that the current does not flow through the coil 302, the contacts A, B are in the first position and the voltage at the coil control input 14 is expected to be lower being the current not flowing through the coil 302 and the shunt resistor 306.

[0182] More generally, the voltage sensed at the coil control input 14 allows to detect the current value flowing through the coil 302.

[0183] Still more generally, a value sensed at the coil control input 14 allows to detect if a current is flowing through the coil 302. In the preferred embodiment described and illustrated herein, the value sensed at the coil control input 14 is the voltage generated by the shunt resistor 306 of the feedback switching circuit 310.

[0184] In further preferred embodiments, the feedback switching circuit may include different types, numbers and / or configurations of components than those shown and / or the electrical parameter sensed at the coil control input may be also different than the voltage.

[0185] According to an aspect of the invention, therefore, the values at the coil control input 14 allows to determine if the coil 302 is working / operating correctly and hence if the relay 300 is working / operating correctly (relay test 4000).

[0186] Preferably, it is determined that the coil 302 is operating correctly both if the voltage at the coil control input 14 is higher when the coil 302 is energized via the coil drive output 12 and if the voltage at the coil control input 14 is lower when the coil 302 is de-energized via the coil drive output 12.

[0187] Conversely, the coil 302 is considered to be operating incorrectly if the voltage values at the coil control input 14 do not match the said expected voltage values according to the energization or de-energization of the coil 302 via the coil drive output 12. Therefore, preferably, coil 302 is considered to be operating incorrectly if the voltage at the coil control input 14 is not higher when the coil 302 is energized via the coil drive output 12 or if the voltage at the coil control input 14 is not lower when the coil 302 is de-energized via the coil drive output 12.

[0188] Preferably, if the result of said relay test 4000 is that the coil 302 is operating incorrectly, or the relay 300 is operating incorrectly, a possible relay failure such as a coil fault is predicted, and safety measures are implemented (steps 4200 or 4500 in Figures 3A and 3B).

[0189] Preferably, a safety measure may comprise, for example, preventing the converter 200 from being activated by the controller 204 so that no electric power is transferred to the electric motor 101, 102 via the relay 300 or de-activating the converter 200 so that no electric power is more transferred to the electric motor 101, 102 via the relay 300 in case the converter 200 was previously activated.

[0190] Another safety measure may comprise generating an appropriate alarm message to the user, preferably via a user interface provided in the dishwasher.

[0191] An alarm message can be, for example, a visual alarm shown on the dishwasher display or sent to an external device such as a smartphone, or a buzzer alarm.

[0192] In a preferred embodiment, the controller 204 is configured to perform the relay test 4000 before the converter 200 is activated to transfer electric power to one of said electric motors 101, 102, as illustrated in Figure 3 A.

[0193] The relay 300 and contacts A, B are firstly driven in the first position or in the second position (step 900) so that the drain electric motor 101 or the wash electric motor 102 is operable.

[0194] The controller 204 is hence configured to perform the relay test 4000 to detect if the relay 300 is operating correctly.

[0195] If the result of said relay test is that the coil 302 is operating correctly, or the relay 300 is operating correctly, the converter 200 is activated to transfer electric power to one of said electric motors 101, 102 (step 4100).

[0196] If the result of said relay test is that the coil 302 is operating incorrectly, or the relay 300 is operating incorrectly, a relay failure is detected, and safety measures are preferably implemented (step 4200), for example preventing the converter 200 from being activated by the controller 204 so that no electric power is transferred to the electric motor 101, 102 via the relay 300 and / or generating an appropriate alarm message to the user, for example via a user interface provided in the dishwasher.

[0197] In a further preferred embodiment, the controller 204 is configured to perform the relay test after the converter 200 has been activated to transfer electric power to one of said electric motors 101, 102, as illustrated in Figure 3B. The relay 300 and contacts A, B are firstly driven in the first position or in the second position (step 900) so that the drain electric motor 101 or the wash electric motor 102 is operable.

[0198] The drain electric motor 101 or the wash electric motor 102 is then powered through the converter 200 (step 950).

[0199] The controller 204 is hence configured to perform the relay test to detect if the relay 300 is operating correctly (step 4000).

[0200] If the result of said relay test is that the coil 302 is operating correctly, or the relay 300 is operating correctly, the converter 200 is kept activated to transfer electric power to one of said electric motors 101, 102 (step 4300).

[0201] If the result of said relay test is that the coil 302 is operating incorrectly, or the relay 300 is operating incorrectly, a relay failure is detected, and safety measures are preferably implemented (step 4500), for example de-activating the converter 200 so that no electric power is more transferred to the electric motor 101, 102 and / or generating an appropriate alarm message to the user, for example via a user interface provided in the dishwasher.

[0202] In a preferred embodiment, the voltage values at the coil control input 14 are detected continuously during the relay test (step 4000). In a further preferred embodiment, the voltage values at the coil control input 14 are detected at predetermined sampling times.

[0203] According to another aspect of the invention, a first feedback circuit 50 is provided between the first electric motor 101 and the controller 204.

[0204] Preferably, the first feedback circuit 50 is electrically connected, at one hand, to the first terminal lead VI of the first electric motor 101 and, on the other hand, to the controller 204, more preferably to a first sense input 16 of the controller 204, also indicated as V sense input 16.

[0205] The V sense input 16 and the first feedback circuit 50 are configured so that at the V sense input 16 a first electrical parameter may be detected: in the preferred embodiment illustrated and described herein, the first electrical parameter is an electric voltage. In different embodiments, the first electrical parameter may of different type, for example a current.

[0206] The first feedback circuit 50 preferably comprises a variety of electrical components to form a circuit, for example two resistors Rl, R2 and a diode DI to form a voltage divider (resistive partitor).

[0207] A second feedback circuit 52 is also provided between the first electric motor 101 and the controller 204.

[0208] Preferably, the second feedback circuit 52 is electrically connected, at one hand, to the second terminal lead W1 of the first electric motor 101 and, on the other hand, to the controller 204, more preferably to a second sense input 18 of the controller 204, also indicated as W sense input 18.

[0209] The W sense input 18 and the second feedback circuit 52 are configured so that at the W sense input 18 a second electrical parameter may be detected: in the preferred embodiment illustrated and described herein, the second electrical parameter is an electric voltage. In different embodiments, the second electrical parameter may of different type, for example a current.

[0210] The second feedback circuit 52 preferably comprises a variety of electrical components to form a circuit, for example two resistors R3, R4 and a diode D2 to form a voltage divider (resistive partitor).

[0211] It is clear that in different embodiments the first and / or the second feedback circuits may include different types, numbers and / or configurations of components than those shown, for example passive components such as capacitors and / or inductors, suitably configured so that an electrical parameter such as voltage or current can be detected at the V sense input 16 and / or at the W sense input 18.

[0212] According to an aspect of the invention, there are provided two test procedures 1000, 2000 to determine if the relay 300 is correctly positioned in the first or in the second position.

[0213] The test procedures 1000, 2000 may be preferably carried out in both the circuit arrangements of Figures 1 and 1A.

[0214] Preferably, the first test procedure 1000 comprises a step of sensing the first electrical parameter, preferably the voltage, at the V sense input 16 in response to a first test signal 502 applied to the relay 300 and the second test procedure 2000 comprises a step of sensing the second electrical parameter, preferably the voltage, at the W sense input 18 in response to a second test signal 602 applied to the relay 300.

[0215] The first test procedure 1000 is described hereinafter with reference to Figures 4 to 7, wherein in Figure 5 the relay 300 and contacts A, B are in their first position while in Figure 6 the relay 300 and contacts A, B are in their second position. The phase diagrams in Figures 7A and 7B show preferred examples of the voltage signals involved in the first test procedure 1000.

[0216] In steps 1010, 1020 (Figure 4) the controller 204 acts to drive the inverter 202 (converter 200) in order to provide a first test signal 502 that is applied to the relay 300.

[0217] In particular, in the first step 1010, the controller 204 drives the inverter 202 through the control connections 8, 9 so that transistors 2a, 2b, 4a, 4b, 6a, 6b are closed / opened according to a first configuration shown in Figures 5 and 6. For the sake of simplicity, in Figures 5 and 6 the transistors 2a, 2b, 4a, 4b, 6a, 6b are schematically shown as switches in their open or closed positions.

[0218] The low-side first and third transistors 2b, 6b are switched on, the low-side second transistor 4b is switched off and the high- side first and third transistors 2a, 6a are switched off.

[0219] In the successive step 1020, the high-side second transistor 4a is opportunely driven to generate the first test signal 502. The high-side second transistor 4a is driven so that it is switched on for a predetermined time P, for example a time P of 100 microseconds. A voltage waveform 502 is thus generated at the first output V of the inverter 202, preferably a rectangular voltage pulse 502 of HVDC amplitude, as depicted in Figures 7 A and 7B. According to this preferred embodiment, therefore, the first test signal 502 is preferably a rectangular voltage pulse 502 at the first output V of the inverter 202.

[0220] In said configuration, electric power is thus provided to the first output V of the converter 200 and no electric power is provided to the second and third outputs W, U of the inverter 202.

[0221] In case the relay 300 and contacts A, B are in their first position (Figure 5), the same voltage waveform 502 is applied to the first terminal lead VI of the first electric motor 101.

[0222] Conversely, in case the relay 300 and contacts A, B are in their second position (Figure 6), the same voltage waveform 502 is applied to the first terminal lead V2 of the second electric motor 102 while no voltage is applied to the first terminal lead VI of the first electric motor 101.

[0223] In a successive step 1030, the voltage waveform at the V sense input 16 is sensed, via the first feedback circuit 50, by the controller 204.

[0224] Accordingly, in case the relay 300 and contacts A, B are in their first position (Figure 5), the voltage waveform 504 sensed at the V sense input 16 is substantially rectangular (Figure 7A). In fact, the voltage waveform 502 which is applied to the first terminal lead VI of the first electric motor 101 is also applied to the resistive partitor formed by resistors Rl, R2. Conversely, in case the relay 300 and contacts A, B are in their second position (Figure 6), a respective zero voltage waveform 506 is sensed at the V sense input 16 (Figure 7B). In fact, the voltage waveform 502 is applied to the first terminal lead V2 of the second electric motor 102, while the voltage level of the first terminal lead VI of the first electric motor 101, which is also applied to the resistive partitor formed by the resistors Rl, R2, is kept at the GND level (zero), since the first terminal lead VI is electrically connected to GND via the path comprising a stator winding of the first electric motor 101, the third terminal lead U1 of the first electric motor 101, the closed low- side first transistor 2b and the first resistor I la.

[0225] The second test procedure 2000 is described hereinafter with reference to Figures 8 to 11, wherein in Figure 9 the relay 300 and contacts A, B are in their first position while in Figure 10 the relay 300 and contacts A, B are in their second position. The phase diagrams in Figures 11 A and 1 IB show preferred examples of the voltage signals involved in the second test procedure 2000.

[0226] In steps 2010, 2020 (Figure 8) the controller 204 acts to drive the inverter 202 (converter 200) in order to provide a second test signal 602 that is applied to the relay 300.

[0227] In particular, in the first step 2010, the controller 204 drives the inverter 202 through the control connections 8, 9 so that transistors 2a, 2b, 4a, 4b, 6a, 6b are closed / opened according to the second configuration shown in Figures 9 and 10. The low-side first and second transistors 2b, 4b are switched on, the low-side third transistor 6b is switched off and the high- side first and second transistors 2a, 4a are switched off.

[0228] In the successive step 2020, the high-side third transistor 6a is opportunely driven to generate the second test signal 602. The high-side third transistor 6a is driven so that it is switched on for a predetermined time P, for example a time P of 100 microseconds. A voltage waveform 602 is thus generated at the second output W of the inverter 202, preferably a rectangular voltage pulse 602 of HVDC amplitude, as depicted in Figures 11 A and 1 IB.

[0229] According to this preferred embodiment, therefore, the second test signal 602 is preferably a rectangular voltage pulse 602 at the second output W of the inverter 202.

[0230] In said configuration, electric power is thus provided to the second output W of the converter 200 and no electric power is provided to the first and third outputs V, U of the inverter 202.

[0231] In case the relay 300 and contacts A, B are in their first position (Figure 9), the same voltage waveform 602 is applied to the second terminal lead W1 of the first electric motor 101.

[0232] Conversely, in case the relay 300 and contacts A, B are in their second position (Figure 10), the same voltage waveform 602 is applied to the second terminal lead W2 of the second electric motor 102 while no voltage is applied to the second terminal lead W1 of the first electric motor 101.

[0233] In a successive step 2030, the voltage waveform at the W sense input 18 is sensed, via the second feedback circuit 52, by the controller 204.

[0234] Accordingly, in case the relay 300 and contacts A, B are in their first position (Figure 9), the voltage waveform 604 sensed at the W sense input 18 is substantially rectangular (Figure 11 A). In fact, the voltage waveform 602 which is applied to the second terminal lead W1 of the first electric motor 101 is also applied to the resistive parti tor formed by resistors R3, R4.

[0235] Conversely, in case the relay 300 and contacts A, B are in their second position (Figure 10), a respective zero voltage waveform 606 is sensed at the W sense input 18 (Figure 11B). In fact, the voltage waveform 602 is applied to the second terminal lead W2 of the second electric motor 102, while the voltage level of the second terminal lead W1 of the first electric motor 101, which is also applied to the resistive partitor formed by the resistors R3, R4, is kept at the GND level (zero), since the second terminal lead W1 is electrically connected to GND via the path comprising a stator winding of the first electric motor 101, the third terminal lead U1 of the first electric motor 101, the closed low- side first transistor 2b and the first resistor I la.

[0236] From above it follows that if everything is working properly, in particular the relay 300 with its contacts A, B are correctly positioned in the first or second position, the waveforms 504, 506, 604, 606 sensed at the V sense input 16 and at the W sense input 18 in response to a first test signal 502 and to a second test signal 502 applied to the relay 300 according to the first and second test procedures 1000, 2000 are the expected ones.

[0237] While according to the embodiment described above the first test procedure 1000 is preferably performed before the second test procedure 2000, in further preferred embodiments the second test procedure 2000 can be performed before the first test procedure 1000. According to an aspect of the invention, a method to determine if the relay 300 is correctly positioned in the first or in the second position, through the first and second test procedures 1000, 2000, is performed each time the relay 300 is driven to switch from the first position to the second position or, vice versa, from the second position to the first position. This method may be preferably carried out in both the circuit arrangements of Figures 1 and 1A.

[0238] The method, as depicted in Figure 12, allows to determine if the relay 300 is correctly positioned in the requested first or second position and hence the actual electric motor 101, 102 may be powered with the specific power required by the specific electric motor 101, 102 through the converter 200.

[0239] According to the invention, therefore, the method is preferably performed in two possible situations: the first situation occurs when the first electric motor 101, namely the drain electric motor 101, needs to be activated and hence the relay 300 is driven to switch in the first position; the second situation occurs when the second electric motor 102, namely the wash electric motor 102, needs to be activated and hence the relay 300 is driven to switch in the second position.

[0240] In the first situation the method is therefore performed when the drain electric motor 101 needs to be activated.

[0241] Referring to Figure 12, firstly the relay 300 and contacts A, B are driven in the first position (step 900), namely the coil drive output 12 is set low, the electronic switch 304 is switched off and the coil 302 is de-energized, as illustrated in Figure 1. The drain electric motor 101 is operable.

[0242] The first test procedure 1000 is then performed, as described above.

[0243] In a successive step 1100, it is determined that the first contact A is correctly positioned in the first position if the waveform 504 sensed at the V sense input 16 matches, or substantially matches, the expected waveform 504 sensed at the V sense input 16 in response to the first test signal 502 applied to the relay 300, in the present case if the waveform 504 sensed at the V sense input 16 matches, or substantially matches, the expected substantially rectangular voltage waveform 504.

[0244] It should be noted that when comparing the sensed waveform with the expected waveform a degree of tolerance is allowed, e.g. the sensed waveform may differ from the expected waveform by up to 20%. The terms “matches” or “substantially matches” are therefore used in the description to satisfy this requirement.

[0245] The second test procedure 2000 is then performed, as described above. In a successive step 2100, it is determined that the second contact B is correctly positioned in the first position if the waveform 604 sensed at the W sense input 18 matches, or substantially matches, the expected waveform 604 sensed at the W sense input 18 in response to the second test signal 602 applied to the relay 300, in the present case if the waveform 604 sensed at the W sense input 18 matches, or substantially matches, the expected substantially rectangular voltage waveform 604.

[0246] At this point, if it has been determined in the previous steps 1100 and 2100 that the relay 300 and the contacts A, B are in the correct first position, then the drain electric motor 101 can be safely operated through the converter 200 with the specific power requested by the drain electric motor 101 (step 2200).

[0247] Conversely, safety measures are preferably implemented, such as preventing the converter 200 from being activated by the controller 204 so that no power is transferred to the drain electric motor 101 via the relay 300 and / or generating an appropriate alarm message to the user, for example via a user interface provided in the dishwasher (step 2300).

[0248] In the second situation the method is performed when the wash electric motor 102 needs to be activated.

[0249] Referring again to Figure 12, firstly the relay 300 and contacts A, B are driven in the second position (step 900), namely the coil drive output 12 is set high, the electronic switch 304 is switched on and the coil 302 is energized. The wash electric motor 102 is operable.

[0250] The first test procedure 1000 is then performed.

[0251] In a successive step 1100, it is determined that the first contact A is correctly positioned in the second position if the waveform 506 sensed at the V sense input 16 matches, or substantially matches, the expected waveform 506 sensed at the V sense input 16 in response to the first test signal 502 applied to the relay 300, in the present case if the waveform 506 sensed at the V sense input 16 matches, or substantially matches, the expected zero voltage waveform 506.

[0252] The second test procedure 2000 is then performed.

[0253] In a successive step 2100, it is determined that the second contact B is correctly positioned in the second position if the waveform 606 sensed at the W sense input 18 matches, or substantially matches, the expected waveform 606 sensed at the W sense input 18 in response to the second test signal 602 applied to the relay 300, in the present case if the waveform 606 sensed at the W sense input 18 matches, or substantially matches, the expected zero voltage waveform 606.

[0254] At this point, if it has been determined in the previous steps 1100 and 2100 that the relay 300 and the contacts A, B are in the correct second position, then the wash electric motor 102 can be safely operated through the converter 200 with the specific power requested by the specific electric motor 101, 102 (step 2200).

[0255] Conversely, safety measures are preferably implemented, such as preventing the converter 200 from being activated by the controller 204 so that no power is transferred to the wash electric motor 102 via the relay 300 and / or generating an appropriate alarm message to the user, for example via a user interface provided in the dishwasher (step 2300).

[0256] From the above it appears that during the test procedures 1000, 2000 the voltage waveforms sensed at the V, W sense inputs 16, 18 allows to determine if the contacts A, B of the relay 300 are in the correct position. Preferably, if the voltage waveforms 504, 604 at the V, W sense inputs 16, 18 are substantially rectangular then the contacts A, B are in the correct first positions with the relay 300 in the first position. If the voltage waveforms 506, 606 at the V, W sense inputs 16, 18 are zero voltage waveforms, then the contacts A, B are in the correct second positions with the relay 300 in the second position.

[0257] In a preferred embodiment, preferably, during the test procedures 1000, 2000 it is sensed if the voltage at the V sense input 16 and at the W sense input 18 is zero or if it is greater than zero, a voltage greater than zero being assumed to indicate a substantially rectangular voltage waveform 504, 604.

[0258] It follows that, as far as the detection of the voltage waveforms at the V sense input 16 and the W sense input 18 is concerned, different preferred methods can be used. In a first preferred embodiment, sense inputs V, W are digital inputs wherein a voltage above e predetermined threshold Th corresponds to the on-state (1) and a voltage below the predetermined threshold Th corresponds to the off- state (0).

[0259] For example, the threshold Th is set as a percentage of the supply voltage Vcc of the controller, for example Th=2 / 3*Vcc.

[0260] Preferably, therefore, detection of the voltage waveforms at V sense input 16 and W sense input 18 comprises the detection of the on-state (voltage greater than zero) or of the off- state (zero voltage) at a detection time Dt.

[0261] For example, with reference to diagrams of Figures 7A and 7B or 11A and 11B, detection of the state at the V sense input 16 and at the W sense input 18 is carried out at a detection time Dt which is set in the middle of the predetermined time period P (observation window) of the voltage waveforms 504, 506, 604, 606.

[0262] In further preferred embodiments, the detection of the voltage waveforms at the V sense input 16 and at the W sense input 18 may be performed differently, for example using an analog input through which the voltage waveform is detected along the duration of said predetermined time period P or is detected at a plurality specified sampling times within said predetermined time period P.

[0263] According to another aspect of the invention, there is provided a test procedure, hereinafter also indicated as third test procedure, that has the aim of verifying that wiring of the electric motors 101, 102 is correct and that the relay 300 is working correctly or, in other words, detecting if the wiring of the electric motors 101, 102 is not correct and / or the relay 300 is not working correctly.

[0264] For example, the incorrect wiring of the electric motors 101, 102 occurs when one of the connectors 102 A, 102B is not properly installed or disconnected and / or a wire is broken / interrupted. Also, for example, the relay 300 is not working correctly when any of its element is damaged, for example a contact A, B and / or the coil 302 is damaged.

[0265] The third test procedure 3000 may be preferably carried out in both the circuit arrangements of Figures 1 and 1A.

[0266] Preferably, the third test procedure 3000 comprises a step of sensing the first electrical parameter, preferably the voltage, at the V sense input 16 and sensing the second electrical parameter, preferably the voltage, at the W sense input 18 in response to a third test signal 702 generated through the converter 200 and applied to the electric motors 101, 102.

[0267] The third test procedure 3000 is described hereinafter with reference to Figures 13 to 16, wherein in Figure 14 the relay 300 and contacts A, B are in their first position while in Figure 15 the relay 300 and contacts A, B are in their second position. The phase diagrams in Figures 16A and 16B show preferred examples of the voltage signals involved in the third test procedure 3000.

[0268] In steps 3010, 3020 the controller 204 acts to drive the inverter 202 (converter 200) in order to provide a third test signal 702 that is applied to the electric motors 101, 102.

[0269] In particular, in the first step 3010, the controller 204 drives the inverter 202 through the control connections 8, 9 so that transistors 2a, 2b, 4a, 4b, 6a, 6b are closed / opened according to a third configuration shown in Figures 14 and 15.

[0270] The low-side second and third transistors 4b, 6b are switched on, the low-side first transistor 2b is switched off and the high- side second and third transistors 4a, 6a are switched off.

[0271] In the successive step 3020, the high- side first transistor 2a is opportunely driven to generate the third test signal 702. The high- side first transistor 2a is driven so that it is switched on for a predetermined time P, for example a time P of 100 microseconds. A voltage waveform 702 is thus generated at the third output U of the inverter 202, preferably a rectangular voltage pulse 702 of HVDC amplitude, as depicted in Figures 16A and 16B. According to this preferred embodiment, therefore, the third test signal 702 is preferably a rectangular voltage pulse 502 at the third output U of the inverter 202.

[0272] In said configuration, electric power is provided to the third output U of the inverter 202 and no electric power is provided to the first and second outputs V, W of the inverter 202.

[0273] In case the relay 300 and contacts A, B are in their first position (Figure 14), the voltage waveform 702 is applied to the third terminal leads Ul, U2 of the electric motors 101, 102 while no voltage is applied to the first terminal lead VI and the second terminal lead W1 of the first electric motor 101. The voltage level of first terminal lead VI of the first electric motor 101, which is also applied to the resistive partitor formed by the resistors Rl, R2, is kept at the GND level (zero), since the first terminal lead VI is electrically connected to GND via the path comprising the first contact A, the closed low-side second transistor 4b and the second resistor 11b. The voltage level of second terminal lead W1 of the first electric motor 101, which is also applied to the resistive partitor formed by the resistors R3, R4, is kept at the GND level (zero), since the second terminal lead W1 is electrically connected to GND via the path comprising the second contact B, the closed low-side third transistor 6b and the third resistor 11c.

[0274] Conversely, in case the relay 300 and contacts A, B are in their second position (Figure 15), the voltage waveform 702 is applied to the third terminal leads Ul, U2 of the electric motors 101, 102 and the same voltage waveform 702 is applied to the first terminal lead V 1 and the second terminal lead W1 of the first electric motor 101 via the stator windings of the first electric motor 101. The voltage waveform 702 is thus also applied to the resistive partitor formed by the resistors R1, R2.

[0275] In a successive step 3030, the voltage waveform at the V sense input 16 and at the W sense input 18 are sensed, via the first feedback circuit 50, by the controller 204. Accordingly, in case the relay 300 and contacts A, B are in their first position (Figure 14), zero voltage waveforms 704, 706 are sensed at the V, W sense inputs 16, 18 (Figure 16A). In fact, as said above, the voltage level of the first terminal lead VI of the first electric motor 101, which is also applied to the resistive partitor formed by the resistors Rl, R2, is kept at the GND level (zero) and the voltage level of the second terminal lead W1 of the first electric motor 101, which is also applied to the resistive partitor formed by the resistors R3, R4, is kept at the GND level (zero).

[0276] Conversely, in case the relay 300 and contacts A, B are in their second position (Figure 15), substantially rectangular voltage waveforms 804, 806 are sensed at the V, W sense inputs 16, 18 (Figure 16B). In fact, as said above, the voltage waveform 702 which is applied to the first terminal lead VI of the first electric motor 101 is also applied to the resistive partitor formed by resistors Rl, R2.

[0277] From above it follows that if everything is working properly, in particular both the wiring of the electric motors 101, 102 is correct and that the relay 300 is working correctly, the waveforms 704, 706, 804, 806 sensed at the V sense input 16 and at the W sense input 18 in response to a third test signal 702 applied to the electric motors 101, 102 according to the third test procedure 3000 are the expected ones. According to an aspect of the invention, a method to determine if the wiring of the electric motors 101, 102 is correct and that the relay 300 is working correctly, through the third test procedure 3000, is performed each time the relay 300 is driven to switch from the first position to the second position or, vice versa, from the second position to the first position.

[0278] The method, as depicted in Figure 17, allows to determine if the wiring of the electric motors 101, 102 is correct and that the relay 300 is working correctly and hence the actual electric motor 101, 102 may be powered by the converter 200.

[0279] This method may be preferably carried out in both the circuit arrangements of Figures 1 and 1A.

[0280] According to the invention, therefore, the method is preferably performed in two possible situations: the first situation occurs when the first electric motor 101, namely the drain electric motor 101, needs to be activated and hence the relay 300 is driven to switch in the first position; the second situation occurs when the second electric motor 102, namely the wash electric motor 102, needs to be activated and hence the relay 300 is driven to switch in the second position.

[0281] In the first situation the method is therefore performed when the drain electric motor 101 needs to be activated.

[0282] Referring to Figure 17, firstly the relay 300 and contacts A, B are driven in the first position (step 900), namely the coil drive output 12 is set low, the electronic switch 304 is switched off and the coil 302 is de-energized, as illustrated in Figure 1. The drain electric motor 101 is operable.

[0283] The third test procedure 3000 is then performed, as described above.

[0284] In a successive step 3400, it is determined that the wiring of the electric motors 101, 102 is correct and that the relay 300 is working correctly if the voltage waveform 704, 804 at the V sense input 16 and the voltage waveform 706, 806 at the W sense input 18 match the expected waveform 704, 804 sensed at the V sense input 16 and the voltage waveform 706, 806 at the W sense input 18 in response to the third test signal 702 applied to the electric motors 101, 102.

[0285] If the result of step 3400 is that the wiring of the electric motors 101, 102 is not correct and / or the relay 300 is not working correctly, safety measures are preferably implemented (step 3500), such as preventing the converter 200 from being activated by the controller 204 so that no electric power is transferred to the drain electric motor 101 via the relay 300 and / or generating an appropriate alarm message to the user, for example via a user interface provided in the dishwasher.

[0286] If the result of step 3400 is that the wiring of the electric motors 101, 102 is correct and the relay 300 is working correctly, then the drain electric motor 101 can be safely operated through the converter 200 (step 3600).

[0287] In the second situation the method is performed when the wash electric motor 102 needs to be activated.

[0288] Referring again to Figure 17, firstly the relay 300 and contacts A, B are driven in the second position (step 900), namely the coil drive output 12 is set high, the electronic switch 304 is switched on and the coil 302 is energized. The wash electric motor 102 is operable.

[0289] The third test procedure 3000 is then performed.

[0290] In the successive step 3400, it is determined that the wiring of the electric motors 101, 102 is correct and that the relay 300 is working correctly if the voltage waveform 704, 804 at the V sense input 16 and the voltage waveform 706, 806 at the W sense input 18 match the expected waveform 704, 804 sensed at the V sense input 16 and the voltage waveform 706, 806 at the W sense input 18 in response to the third test signal 702 applied to the electric motors 101, 102.

[0291] If the result of step 3400 is that the wiring of the electric motors 101, 102 is not correct and / or the relay 300 is not working correctly, safety measures are preferably implemented (step 3500), such as preventing the converter 200 from being activated by the controller 204 so that no electric power is transferred to the wash electric motor 102 via the relay 300 and / or generating an appropriate alarm message to the user, for example via a user interface provided in the dishwasher. If the result of step 3400 is that the wiring of the electric motors 101, 102 is correct and the relay 300 is working correctly, then the wash electric motor 102 can be safely operated through the converter 200 (step 3600).

[0292] In a preferred embodiment, the third test procedure 3000 may be preferably performed at any time during a washing program to determine that the wiring of the electric motors 101, 102 is correct and that the relay 300 is working correctly. In a further preferred embodiment, the third test procedure 3000 is preferably performed before the first and second test procedures 1000, 2000 described above. This preferred embodiment of the method is depicted in Figure 18. This method may be preferably carried out in both the circuit arrangements of Figures 1 and 1 A. The method according to this embodiment differs from the method described with reference to Figure 12 in that a third test procedure 3000 is performed after the relay 300 and contacts A, B are driven in the first or second position (step 900) and before the first and second test procedures (steps 1000 and 2000).

[0293] According to this embodiment, therefore, with the third test procedure (step 3000) it is firstly determined if the wiring of the electric motors 101, 102 is correct and if the relay 300 is working correctly (step 3400) and successively with the first and second test procedures (step 1000 and step 2000) it is determined if the contacts A, B of the relay 300 are in the correct position (step 2100).

[0294] Accordingly, if the result of the three test procedures (step 3400, step 1100 and step 2100) is positive, the first electric motor 101 (drain electric motor 101) or the second electric motor 102 (wash electric motor 102) is operated (step 2200).

[0295] Conversely, if the result of at least one the three test procedures (step 3400, step 1100 and step 2100) is negative, an appropriate safety measure is taken (step 3500 or step 2300), such as preventing the converter 200 from being activated by the controller 204 so that no electric power is transferred to the electric motor 101, 102 via the relay 300 and / or generating an appropriate alarm message to the user, for example via a user interface provided in the dishwasher.

[0296] According to another aspect of the invention, there is further provide a method wherein before determining if the relay 300 is correctly positioned in the first or second position, for example as in the methods described above with reference to Figures 12, a relay test (step 4000) is performed to detect that the relay 300 is operating correctly.

[0297] This preferred embodiment of the method is depicted in Figure 19. This method may be preferably carried out in the circuit arrangement of Figure 1 which is equipped with the feedback switching circuit 310.

[0298] The relay 300 and contacts A, B are firstly driven in the first position or in the second position (step 900) so that the first electric motor 101 (drain electric motor 101) or the second electric motor 102 (wash electric motor 102) is operable.

[0299] In a successive step, a relay test (step 4000) is performed to detect that the relay 300 is operating correctly, preferably with the method described above.

[0300] If the result of said relay test (step 4000) is that the coil 302 is operating incorrectly, or the relay 300 is operating incorrectly, a possible relay failure such as a coil fault is predicted, and safety measures are implemented (step 4100).

[0301] Preferably, a safety measure may comprise, for example, preventing the converter 200 from being activated by the controller 204 so that no electric power is transferred to the electric motor 101, 102 via the relay 300 and / or generating an appropriate alarm message to the user, for example via a user interface provided in the dishwasher.

[0302] Conversely, if the result of said relay test (step 4000) is that the coil 302 is operating correctly, the method proceeds by determining if the relay 300 is correctly positioned in the requested first or second position and hence the actual electric motor 101, 102 may be powered with the specific power requested by the specific electric motor 101, 102 (step 2200).

[0303] Preferably, the method proceeds as illustrated and described with reference to Figure 12, i.e. by performing the first test procedure 1000, the step 1100 of determining if the first contact A is correctly in the first or second position, the second test procedure 2000 and the step 2100 of determining if the second contact B is correctly in the first or second position.

[0304] Finally, advantageously, if it has been determined that the relay 300 and the contacts A, B are in the correct first or second position, then the drain electric motor 101 or the wash electric motor 102 can be safely operated through the converter 200 with the specific power requested by the specific electric motor 101, 102 (step 2200).

[0305] Conversely, safety measures are preferably implemented (step 2300), such as preventing the converter 200 from being activated by the controller 204 so that no power is transferred to the drain electric motor 101 or the wash electric motor 102 via the relay 300 and / or generating an appropriate alarm message to the user, for example via a user interface provided in the dishwasher.

[0306] According to another aspect of the invention, there is provided a further method, depicted in Figure 20, that differs from the method described with reference to Figure 19 in that a third test procedure (step 3000) is preferably performed after the relay test (step 4000) and before determining if the relay 300 is correctly positioned in the requested first or second position. This method may be preferably carried out in the circuit arrangement of Figure 1 which is equipped with the feedback switching circuit 310.

[0307] The relay 300 and contacts A, B are firstly driven in the first position or in the second position (step 900) so that the first electric motor 101 (drain electric motor 101) or the second electric motor 102 (wash electric motor 102) is operable.

[0308] In a successive step, a relay test (step 4000) is performed to detect that the relay 300 is operating correctly, preferably with the method described above.

[0309] If the result of said relay test (step 4000) is that the coil 302 is operating incorrectly, or the relay 300 is operating incorrectly, a possible relay failure such as a coil fault is predicted, and safety measures are implemented (step 4100).

[0310] Preferably, a safety measure may comprise, for example, preventing the converter 200 from being activated by the controller 204 so that no electric power is transferred to the electric motor 101, 102 via the relay 300 and / or generating an appropriate alarm message to the user, for example via a user interface provided in the dishwasher.

[0311] Conversely, if the result of said relay test (step 4000) is that the coil 302 is operating correctly, the third test procedure (step 3000) is performed to determine if the wiring of the electric motors 101, 102 is correct and if the relay 300 is working correctly, as described above with reference to Figure 13.

[0312] If the result of the third test procedure (step 3000) is that the wiring of the electric motors 101, 102 is correct and that the relay 300 is working correctly, the method proceeds by determining if the relay 300 is correctly positioned in the requested first or second position and hence the actual electric motor 101, 102 may be powered with the specific power requested by the specific electric motor 101, 102 through the converter 200.

[0313] Preferably, the method proceeds as illustrated and described with reference to Figure 12, i.e. by performing the first test procedure 1000, the step 1100 of determining if the first contact A is correctly in the first or second position, the second test procedure 2000 and the step 2100 of determining if the second contact B is correctly in the first or second position.

[0314] Finally, advantageously, if it has been determined that the relay 300 and the contacts A, B are in the correct first or second position, then the drain electric motor 101 or the wash electric motor 102 can be safely operated through the converter 200 with the specific power requested by the specific electric motor 101, 102 (step 2200).

[0315] Conversely, safety measures are preferably implemented (step 2300), such as preventing the converter 200 from being activated by the controller 204 so that no power is transferred to the drain electric motor 101 or the wash electric motor 102 via the relay 300 and / or generating an appropriate alarm message to the user, for example via a user interface provided in the dishwasher.

[0316] In the preferred embodiment of the circuit arrangement shown and described above, the switching device 300 comprises a two-contact relay with a respective coil 302, there is provided a single switch drive output 12 for a single electronic switch 304 and a single switch control input 14 for sensing a switching electrical parameter coming from the feedback switching circuit 310.

[0317] In variant embodiments, however, the switching device could be made in a different manner, for example, by using two separate relays, each comprising a single contact which can be positioned in the first and second position through a respective coil.

[0318] In a first embodiment, then, the two relays could be separately driven by means of two corresponding switch drive outputs provided at the controller and two switch control inputs provided to detect electrical parameters coming from two separate feedback switching circuit.

[0319] In a further embodiment, the two relays could be commonly driven by means of a common switch drive output and a switch control input could be provided to detect a common electrical parameter coming from a feedback switching circuit.

[0320] In any case, the controller would drive the two separate relays of the switching device to move the contacts to the first and second positions according to the timing described above, preferably by moving the contacts simultaneously.

[0321] It has thus been shown that the present invention allows all the set objects to be achieved. In particular, the system to the invention allows a more efficient and safe control management system relating two pump assemblies in a washing appliance. While the present invention has been described with reference to the particular embodiments shown in the figures, it should be noted that the present invention is not limited to the specific embodiments illustrated and described herein; on the contrary, further variants of the embodiments described herein fall within the scope of the present invention, which is defined in the claims.

Claims

CLAIMS1. A washing appliance comprising:- a container apt to receive articles to be washed;- a first pump assembly equipped with a first three-phase electric motor (101) having three terminal leads (Ul, VI, Wl);- a second pump assembly equipped with a second three-phase electric motor (102) having three terminal leads (U2, V2, W2);- a controllable power converter (200) having three outputs (U, V, W) for providing electric power to said electric motors (101, 102);- a control device (204) to control said controllable power converter (200);- a switching device (300) interposed between said controllable power converter (200) and said electric motors (101, 102), said switching device (300) being configured to be disposed in a first position to operate said first electric motor (101) and a second position to operate said second electric motor (102), wherein first and second outputs (V, W) of said converter (200) are connected to said switching device (300), first and second terminal leads (VI, Wl) of said first electric motor (101) are connected to said switching device (300) and first and second terminal leads (V2, W2) of said second electric motor (102) are connected to said switching device (300), the third output (U) of said converter (200) being directly connected to both said first terminal lead (Ul) of said first electric motor (101) and said first terminal lead (U2) of said second electric motor (102), said switching device (300) comprising:- a first contact (A) displaceable in a first position to connect said first output (V) of said converter (200) to said first terminal lead (VI) of said first electric motor (101) when said switching device (300) is in said first position and in a second position to connect said first output (V) of said converter (200) to said first terminal lead (V2) of said second electric motor (102) when said switching device (300) is in said second position;- a second contact (B) displaceable in a first position to connect said second output (W) of said converter (200) to said second terminal lead (Wl) of said first electric motor (101) when said switching device (300) is in said first position and in a second position to connect said second output (W) of said converter (200) to said second terminal (W2) lead of said second electric motor (102) when said switching device (300) is in said second position;- at least one actuator (302) acting on said first contact (A) for displacing itin said first position or said second position and acting on said second contact (B) for displacing it in said first position or said second position;- said control device (204) further comprising at least one switch drive output (12) to activate or de-activate said at least one actuator (302) for driving said switching device (300) in said first position or said second position;- a first feedback circuit (50) electrically connected to a first terminal lead (VI) of said first electric motor (101) and to said control device (204);- a second feedback circuit (52) electrically connected to a second terminal lead (Wl) of said first electric motor (101) and to said control device (204);- said control device (204) further comprising a first sense input (16) for sensing a first electrical parameter coming from said first feedback circuit (50) and a second sense input (18) for sensing a second electrical parameter coming from said second feedback circuit (52).

2. Appliance according to claim 1, wherein it further comprises at least one feedback switching circuit (310) electrically connected to said actuator (302) and to said control device (204) and said control device (204) further comprising at least one switch control input (14) for sensing a switching electrical parameter coming from said at least one feedback switching circuit (310).

3. Appliance according to claim 1 or 2, wherein said actuator (302) comprises a coil (302) apt to be energized to switch said switching device (300) from said first position to said second position and apt to be de-energized to switch said switching device (300) from said second position to said first position and said at least one feedback switching circuit (310) is electrically connected to said coil and said control device (204).

4. Appliance according to any of the preceding claims, wherein said controllable power converter (200) is as a three-phase voltage system.

5. Appliance according to claim 4, wherein said three-phase voltage system is a three-phase inverter (202) comprising six inverter switches (2a, 2b, 4a, 4b, 6a, 6b) arranged in a three-phase bridge with three legs each having a pair of switches (2a, 2b; 4a, 4b; 6a, 6b).

6. Appliance according to any of the preceding claims, wherein said switching electrical parameter and / or said first electrical parameter and / or said second electrical parameter electrical parameter is an electric voltage.

7. Appliance according to any of the preceding claims, wherein said first feedback circuit (50) is configured to provide said first electrical parameter as an electricvoltage or a current and / or said second feedback circuit (52) is configured to provide said second electrical parameter as an electric voltage or a current, wherein said first feedback circuit (50) and / or said second feedback circuit (52) is preferably a voltage divider, more preferably a resistive partitor.

8. Method for operating a washing appliance according to any of the preceding claims characterized in that said method comprises the steps of: a) activate or de-activate said at least one actuator (302), through said switch drive output (12), for positioning said switching device (300) in said first position wherein said first and second contacts (A, B) are in said first position or positioning said switching device (300) in said second position wherein said first and second contacts (A, B) are in said second position; b) performing a method for evaluating if said switching device (300) is correctly positioned in said first position or in said second position comprising the steps of: bl) performing a first test procedure comprising the steps of:- applying a first test signal to said switching device (300) by driving said converter (200) to provide electric power to said first output (V) of said converter (200) and not to provide electric power to said second and third outputs (W, U) of said converter (200);- sensing said first electrical parameter;- determining that said first contact (A) is correctly in said first position if said first electrical parameter substantially matches an expected reference parameter indicative of said first terminal lead (VI) of said first electric motor (101) being powered or determining that said first contact (A) is correctly in said second position if said first electrical parameter substantially matches an expected reference parameter indicative of said first terminal lead (VI) of said first electric motor (101) being not powered; b2) performing a second test procedure comprising the steps of:- applying a second test signal to said switching device (300) by driving said converter (200) to driving said converter (200) to provide electric power to said second output (W) of said converter (200) and not to provide electric power to said first and third outputs (V, U) of said converter (200);- sensing said second electrical parameter;- determining that said second contact (B) is correctly in said firstposition if said second electrical parameter substantially matches an expected reference parameter indicative of said second terminal lead (Wl) of said first electric motor (101) being powered or determining that said second contact (B) is correctly in said second position if said second electrical parameter substantially matches an expected reference parameter indicative of said second terminal lead (Wl) of said first electric motor (101) being not powered; c) if the result of said first and second test procedures is that said first contact (A) and said second contact (B) are correctly in said first position, operating said first electric motor (101) through said converter (200), or if the result of said first and second test procedures is that said first contact (A) and said second contact (B) are correctly in said second position, operating said second electric motor (102) through said converter (200).

9. Method according to claim 8, wherein after steps bl) and b2) the method comprises the step of: d) if the result of said first test procedure is that said first contact (A) or said second contact (B) is not correctly in said first position or if the result of said second test procedure is that said first contact (A) or said second contact (B) is not correctly in said second position, performing at least one of the following:- preventing operating said first electric motor (101) or said second electric motor (102);- generating an alarm message.

10. Method according to claim 8 or 9, wherein after step a) and before step b) the method comprises the following steps: e) performing a third test procedure for verifying that the wiring of said electric motors (101, 102) is correct and that said switching device (300) is working correctly, said third test procedure comprising the steps of:- applying a third test signal to said switching device (300) by driving said converter (200) to provide electric power to said third output (U) of said converter (200) and not to provide electric power to said first and second outputs (V, W) of said converter (200);- sensing said first electrical parameter and said second electrical parameter;- determining that the wiring of said electric motors (101, 102) is correct and that said switching device (300) is working correctly if said first electrical parameter substantially matches an expected reference parameterindicative of both said third terminal leads (Ul, U2) of said first and second electric motors (101, 102) being powered and if said second electrical parameter substantially matches an expected reference parameter indicative of both said third terminal leads (Ul, U2) of said first and second electric motors (101, 102) being powered; f) if the result of said third test procedure is that the wiring of said electric motors (101, 102) is correct and said switching device (300) is working correctly, proceeding with step b).

11. Method according to claim 10, wherein after step e) the method comprises the step of: g) if the result of said third test procedure is that the wiring of said electric motors (101, 102) is not correct and / or said switching device (300) is not working correctly, performing at least one of the following:- preventing operating said first electric motor (101) or said second electric motor (102);- generating an alarm message.

12. Method according to claim 8 or 9 when depending on claim 2, wherein after step a) and before step b) the method comprises the steps of: h) performing a switching device test for evaluating that said switching device (300) is operating correctly, said switching device test comprising the steps of:- sensing said switching electrical parameter;- determining that said switching device (300) is operating correctly if said switching electrical parameter substantially matches an expected reference parameter indicative of said actuator (302) being activated or de-activated; i) if the result of said switching device test is that said switching device (300) is operating correctly, proceeding with step b).

13. Method according to claim 12, wherein after step h) the method comprises the step of:1) if the result of said switching device test is that said switching device (300) is operating incorrectly, performing at least one of the following:- preventing operating said first electric motor (101) or said second electric motor (102);- generating an alarm message.

14. Method according to claim 8 or 9 when depending on claim 2, wherein after step a) and before step b) the method comprises the steps of:h) performing a switching device test for evaluating that said switching device (300) is operating correctly, said switching device test comprising the steps of:- sensing said switching electrical parameter;- determining that said switching device (300) is operating correctly if said switching electrical parameter substantially matches an expected reference parameter indicative of said actuator (302) being activated or de-activated; i) if the result of said switching device test is that said switching device (300) is operating correctly, then: e) performing a third test procedure for verifying that the wiring of said electric motors (101, 102) is correct and that said switching device (300) is working correctly, said third test procedure comprising the steps of:- applying a third test signal to said switching device (300) by driving said converter (200) to provide electric power to said third output (U) of said converter (200) and not to provide electric power to said first and second outputs (V, W) of said converter (200);- sensing said first electrical parameter and said second electrical parameter;- determining that the wiring of said electric motors (101, 102) is correct and that said switching device (300) is working correctly if said first electrical parameter substantially matches an expected reference parameter indicative of both said third terminal leads (Ul, U2) of said first and second electric motors (101, 102) being powered and if said second electrical parameter substantially matches an expected reference parameter indicative of both said third terminal leads (Ul, U2) of said first and second electric motors (101, 102) being powered; f) if the result of said third test procedure is that the wiring of said electric motors (101, 102) is correct and said switching device (300) is working correctly, proceeding with step b).

15. Method according to claim 14, wherein after step h) the method comprises the step of:1) if the result of said switching device test is that said switching device (300) is operating incorrectly, performing at least one of the following:- preventing operating said first electric motor (101) or said second electric motor (102);- generating an alarm message.

16. Method according to claim 14 or 15, wherein after step e) the method comprises the step of: g) if the result of said third test procedure is that the wiring of said electric motors (101, 102) is not correct and / or said switching device (300) is not working correctly, performing at least one of the following:- preventing operating said first electric motor (101) or said second electric motor (102);- generating an alarm message.

17. Method for operating a washing appliance according to any of the claims 1 to 7, wherein it comprises the steps of: a) performing a test procedure for verifying that the wiring of said electric motors (101, 102) is correct and that said switching device (300) is working correctly, said test procedure comprising the steps of:- applying a test signal to said switching device (300) by driving said converter (200) to provide electric power to said third output of said converter (200) and not to provide electric power to said first and second outputs of said converter (200);- sensing said first electrical parameter and said second electrical parameter;- determining that the wiring of said electric motors (101, 102) is correct and that said switching device (300) is working correctly if said first electrical parameter substantially matches an expected reference parameter indicative of both said third terminal leads of said first and second electric motors (101, 102) being powered and if said second electrical parameter substantially matches an expected reference parameter indicative of both said third terminal leads of said first and second electric motors (101, 102) being powered; b) if the result of said test procedure is that the wiring of said electric motors (101, 102) is correct and said switching device (300) is working correctly, operating said first electric motor (101) through said converter (200) or operating said second electric motor (102) through said converter (200).

18. Method according to claim 17, wherein after step a) the method comprises the step of: c) if the result of said test procedure is that the wiring of said electric motors (101, 102) is not correct and / or said switching device (300) is not working correctly,performing at least one of the following:- preventing operating said first electric motor (101) or said second electric motor (102);- generating an alarm message.

19. Method for operating a washing appliance according to any of the claims 2 to 7 when depending on claim 2, characterized in that it comprises the steps of: a) driving said switching device (300), through said switch drive output (12), for activating or de-activating said actuator (302) to drive said switching device (300) from said first position to said second position or from said second position to said first position; b) performing a switching device test for evaluating that said switching device (300) is operating correctly, said switching device test comprising the steps of:- sensing said switching electrical parameter;- determining that said switching device (300) is operating correctly if said switching electrical parameter substantially matches an expected reference parameter indicative of said actuator (302) being activated or de-activated; c) if the result of said switching device test is that said switching device (300) is operating correctly, performing one of the following step dl) or d2): dl) operating said first electric motor (101) through said converter (200) or operating said second electric motor (102) through said converter (200); d2) performing a method for evaluating if said switching device (300) is correctly positioned in said first position or in said second position by evaluating said first electrical parameter at said first sense input (16) and said second electrical parameter at said second sense input (18) and if the result of said method is that said first contact (A) and said second contact (B) are correctly in said first position, operating said first electric motor (101) through said converter (200), or if the result of said method is that said first contact (A) and said second contact (B) are correctly in said second position, operating said second electric motor (102) through said converter (200).

20. Method according to claim 19, wherein after step b) the method comprises the step of: e) if the result of said switching device test is that said switching device (300) is operating incorrectly, performing at least one of the following:- preventing operating said first electric motor (101) or said second electricmotor (102);- generating an alarm message.

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