drive system

Abstract

The invention relates to a drive system with a three-phase motor (M1), with a single-phase motor (M2) and with a control circuit. with three half-bridges (H1-H3) which are designed and configured to control the three-phase motor (M1), with three measuring resistors (R1-R3), preferably shunts (R1-R3), which are designed and configured to detect the currents of the three half-bridges (H1-H3), with a fourth half-bridge (H4) which is designed and configured to control the single-phase motor (M2), with a fourth measuring resistor (R4), preferably shunt (R4), which is designed and configured to detect the current of the fourth half-bridge (H4), wherein one of the three half-bridges (H1-H3) is designed and configured to control the three-phase motor (M1) and also to control the single-phase motor (M2), and with a control unit (S) which is designed and set up to operate the four half-bridges (H1-H4).

Description

[0001] The invention relates to a drive system and a household appliance with such a drive system.

[0002] Electric motors include synchronous motors, which can be operated single-phase with alternating current (AC) or multi-phase with three-phase AC. In each case, a constantly magnetized rotor is used. This rotor can be powered by permanent magnets or external electromagnetic excitation. The term "synchronous motor" derives from the fact that the rotor is driven synchronously by a rotating magnetic field in the stator. Thus, during operation, the synchronous motor exhibits synchronous motion with the AC voltage, and its rotational speed is linked to the frequency of the AC voltage via the number of pole pairs in the stator.

[0003] Multi-strand permanent magnet synchronous motors are typically operated via a frequency converter, which enables controlled operation by determining the direction of rotation, speed, and torque of the synchronous motor via the frequency and amplitude of the frequency converter's output AC voltage. This allows for targeted control of the synchronous motor's rotational behavior, for example, during startup and depending on the load being driven.

[0004] A disadvantage is that such frequency converters incur additional costs and can require extra installation space. Besides the frequency converter itself, these costs can arise from additional electronics within the drive system. These costs are particularly undesirable in various simple applications, such as basic pumps like the drain pumps in washing machines, because the control and regulation capabilities of the synchronous motor provided by the frequency converter are not needed for these applications, thus rendering the additional cost of the frequency converter unprofitable. Such simple applications, like drain pumps in washing machines, include pumping the water out of the wash chamber or recirculating it. In both cases, controlled operation of the respective pump motor is not required.

[0005] As a cost-effective alternative to frequency converter-operated synchronous motors, unregulated single-phase synchronous motors are commonly used to drive simple applications such as drain pumps in washing machines. These applications typically employ permanent magnet single-phase synchronous motors, eliminating the need for electrical contact between the stator and rotor via slip rings or brushes.

[0006] As already mentioned, it is also advantageous for permanent magnet single-phase synchronous motors that, during operation, they perform a motion synchronous with the AC voltage, the rotational speed of which is linked to the frequency of the AC voltage via the number of pole pairs of the stator. Thus, operating a permanent magnet single-phase synchronous motor at the frequency of the mains AC voltage is very simple, and costly controllers and frequency converters can be dispensed with. Instead, simple control of the single-phase synchronous motor via an H-bridge, which can be operated by a control unit, is sufficient. This is particularly beneficial for simple, unregulated applications with constant speed, such as drain pumps in washing machines.

[0007] If several such single-phase synchronous motors are used in a device, for example, a washing machine with one single-phase synchronous motor for the circulation pump and a second single-phase synchronous motor for the drain pump, then one H-bridge and one control unit are required for each single-phase synchronous motor. This applies accordingly to other motors, and especially to two-phase or three-phase synchronous motors, or combinations thereof. For example, in a device with one single-phase synchronous motor and one three-phase synchronous motor, each requires its own three-phase bridge and control unit to operate simultaneously, i.e., in parallel.

[0008] The disadvantage of this is that in any case, the additional three-phase bridges can increase the manufacturing costs in terms of material and assembly effort, the space required in the device or on the electronics, the power consumption and / or the waste heat generated.

[0009] In other words, technical products often have multiple motors controlled by electronics. In the simplest case, the motors are switched on and off. However, due to increasing demands regarding energy consumption and product comfort, electronic motor control is becoming more and more common.

[0010] More and more three-phase motors are being used for drives that operate over a large period of time during device operation, such as the drive of the washing machine drum, the drive of the dishwasher circulation pump, the drive of the drum and blower in the tumble dryer, the drive of compressors for heat pumps, including in tumble dryers, and the drive of vacuum cleaner blowers.

[0011] In addition, technical devices also contain motors with shorter operating times and / or lower power output. These are responsible for pumping water, positioning water channels, and mechanically processing floors, such as the brush roller in a vacuum cleaner. For the sake of simplicity, these motors are often only switched on and off and operate at a constant speed. While speed control would be advantageous, it is often omitted for cost reasons.

[0012] To operate the small motor in such technical devices, the maximum available voltage for the large motor must be significantly reduced. The application of the third harmonic of the drive frequency to all phases, which is usually done to fully utilize the DC link voltage and thus increase power, must be eliminated. The voltage of the smaller motor, including the voltage drop across the coupling capacitor, reduces the voltage available for the main motor accordingly. This loss of available voltage must be compensated for by a correspondingly higher current draw. This requires larger conductor cross-sections and semiconductors with higher current-carrying capacities.

[0013] Another disadvantage is that the coupling capacitor for the small motor is a necessary component, which increases the cost.

[0014] The invention thus addresses the problem of providing a drive system of the type described above, which can operate a three-phase motor and a single-phase motor independently of each other with less electronic or circuitry complexity than previously known. In particular, the components of the three-phase motor's control circuit should be able to be used to control a further, smaller single-phase motor with minimal effort. Preferably, the speed of a smaller single-phase motor should be adjustable. Preferably, the current draw and / or phase shift of a smaller single-phase motor should be able to be detected by the control circuit for optimized control. This should be achieved in a more cost-effective, space-saving, energy-efficient, and / or heat-generating manner.At least an alternative to known drive systems of this type should be created.

[0015] According to the invention, this problem is solved by a drive system and by a household appliance with the features of the independent claims. Advantageous embodiments and further developments of the invention are described in the following dependent claims.

[0016] Thus, the present invention relates to a drive system comprising a three-phase motor, a single-phase motor and a control circuit. with three half-bridges which are designed and configured to control the three-phase motor, with three measuring resistors, preferably shunts, which are designed and configured to detect the currents of the three half-bridges, with a fourth half-bridge, which is designed and equipped to control the single-phase motor, with a fourth measuring resistor, preferably a shunt, which is designed and configured to detect the current of the fourth half-bridge, wherein one of the three half-bridges for controlling the three-phase motor is further designed and configured for controlling the single-phase motor, and with a control unit which is designed and equipped to operate the four half-bridges.

[0017] In contrast to the current state of the art, this eliminates the need for an additional half-bridge, allowing one of the existing half-bridges of the three-phase motor to be used to operate both motors simultaneously. This can reduce the complexity and costs accordingly. It can also save weight and installation space, as well as lower energy consumption.

[0018] According to one aspect of the invention, the control circuit is designed and configured to add half the amplitude of the voltage of the single-phase motor to the three phases of the three-phase motor. This can increase the output voltages of the three half-bridges accordingly, in order to operate the single-phase motor in addition, without restricting the operation of the three-phase motor.

[0019] According to a further aspect of the invention, the control circuit is designed and configured to operate the fourth half-bridge such that its output voltage corresponds to the output voltage of the three half-bridges that additionally drive the single-phase motor, less half the voltage of the single-phase motor. This allows the motor voltage of the single-phase motor to be provided in a simple manner.

[0020] According to a further aspect of the invention, the control circuit is designed and configured to operate the half-bridge that additionally controls the single-phase motor in such a way that the current of this half-bridge corresponds to the measured current of the corresponding measuring resistor minus the measured current of the measuring resistor of the fourth half-bridge. This allows for the consideration and correction of the fact that the current supplied by the half-bridge that additionally controls the single-phase motor contains components from both motors.

[0021] According to another aspect of the invention, the three phases of the three-phase motor are connected to a neutral point, with the single-phase motor being arranged between the fourth half-bridge and the neutral point of the three-phase motor. The advantage of this is that both motors can be operated without restrictions. The entire DC link voltage is available to the three-phase motor without limitations. The single-phase motor can be designed with a higher voltage and lower current, which can be advantageous in terms of implementation (cost).

[0022] According to another aspect of the invention, the three-phase motor is a three-phase AC motor, preferably a three-phase synchronous motor. This can enable the implementation of the drive system with such motors.

[0023] According to another aspect of the invention, the single-phase motor is a single-phase AC motor, preferably a single-phase synchronous motor. This can enable the implementation of the drive system with such motors.

[0024] The present invention also relates to a household appliance, preferably a washing machine or a dishwasher, with at least one drive system as described above. The household appliance can, in particular, be a washing machine with the three-phase motor as the drum drive and the single-phase motor as the drain pump, a dishwasher with the three-phase motor as the circulation pump and the single-phase motor as the drain pump, a vacuum cleaner or a robotic vacuum cleaner with the three-phase motor as the blower motor and the single-phase motor as the electric brush, or a dryer with the three-phase motor as the blower or drum drive and the single-phase motor as the drain pump. However, the drive system according to the invention can also be applied to completely different products from other industries. This allows the properties and advantages of a drive system according to the invention to be implemented and utilized.

[0025] Several embodiments of the invention are shown schematically in the drawings and are described in more detail below. It shows Fig. 1 a circuit diagram of a drive system according to the state of the art with a three-phase motor and with a single-phase motor, each connected to a converter; Fig. 2 a circuit diagram of a drive system according to the invention in a first embodiment with the three-phase motor and with the single-phase motor on a common half-bridge; Fig. 3 a time course of the voltage of the four half-bridge outputs of the circuit diagram of the Fig. 2; Fig. 4. a time course of the corresponding calculated sinusoidal waveforms of the voltage at the motors of the circuit diagram of the Fig. 2; Fig. 5 a circuit diagram of a drive system according to the invention in a second embodiment with the three-phase motor and with the single-phase motor on a common half-bridge; Fig. 6. a time course of the voltages of the four half-bridge outputs of the circuit diagram of the Fig. 5; and Fig. 7 a time course of the corresponding calculated sinusoidal waveforms of the voltages at the motors of the circuit diagram of the Fig. 5.

[0026] Fig. Figure 1 shows a circuit diagram of a drive system according to the state of the art with a three-phase motor M1 and with a single-phase motor M2, each connected to an inverter.

[0027] An AC voltage of 230V is supplied to the drive system via voltage inputs L and N. This AC voltage is converted into a DC voltage (intermediate link voltage) by a rectifier GL and then smoothed by a smoothing capacitor C. The smoothed intermediate link voltage feeds a first converter in the form of a three-phase bridge with three half-bridges H1-H3, each containing a pair of power semiconductors (not labeled). These semiconductors are operated and controlled by a common driver D and each half-bridge incorporates a shunt resistor R1-R3. The driver D is controlled by a control unit S. The driver D controls the two power semiconductors in each half-bridge H1-H3. The first three-phase bridge, or rather its half-bridges H1-H3, can thus generate a first phase U, a second phase V, and a third phase W, and thereby supply and operate a three-phase motor M1.

[0028] This applies accordingly to a single-phase motor M2, for which a second converter in the form of a second three-phase bridge is provided as two further half-bridges H4-H5 in parallel to the three half-bridges H1-H3 of the first converter. The two further half-bridges H4-H5 are also operated and controlled by the common driver D and each also has a measuring resistor R4-R5 in the form of a shunt R4-R5. To control and operate the five half-bridges H1-H5 in total, the control unit S has a three-phase sine wave generator G-M1 of the three-phase motor M1, a sine wave generator G-M2 of the single-phase motor M2, and an H3 generator G-H3. This results in a control circuit according to the circuit diagram of the Fig. 1.

[0029] According to the state of the art, see Fig. 1. The two described motors M1 and M2 are thus controlled by a common control circuit, but separately from each other, by connecting each individual motor terminal to one of the inverter half-bridges H1-H5. The three-phase motor M1 has three terminals and the two-phase motor M2 has two terminals, so a total of five half-bridges H1-H5 are required, see Figure 1. Fig. 1.

[0030] Both inverters, i.e., the first inverter for the three-phase motor M1 (consisting of the three left half-bridges H1-H3) and the second inverter for the single-phase motor M2 (consisting of the two right half-bridges H4-H5), are supplied from the common DC link. The three left half-bridges H1-H3 for operating the three-phase motor M1 are supplied with sinusoidal voltages generated by pulse-width modulation (PWM), which are phase-shifted by 120° relative to each other. The resulting phase currents are measured via the measuring resistors R1-R3 and fed back to the control unit S. To maximize the utilization of the DC link voltage, a sinusoidal voltage with three times the phase frequency and a suitable amplitude (generated by the H3 generator G-H3) is additionally superimposed on all three phases.

[0031] To reduce the circuitry complexity compared to the known drive system, in accordance with the state of the art... Fig. 1 The exemplary embodiments of two circuits according to the invention and the control principles required for them are explained below and illustrated in the corresponding figures.

[0032] Fig. Figure 2 shows a circuit diagram of a drive system according to a first embodiment with the three-phase motor M1 and with the single-phase motor M2 on a common half-bridge H4. Fig. Figure 3 shows a time course of the four half-bridge outputs of the circuit diagram of the Fig. 2. Fig. Figure 4 shows a time course of the corresponding calculated sine waveforms of the circuit diagram. Fig. 2 on the two motors M1, M2.

[0033] In contrast to the prior art, here the single-phase motor M2 is connected between any half-bridge of the first converter of the three-phase motor M1 – in the considered embodiment, at the second half-bridge H2 – and to an additional fourth half-bridge H4. Thus, unlike the prior art, the further fifth half-bridge H5 is omitted, and instead, one half-bridge of motor M1 – here the second half-bridge H2 – is used for both motors M1 and M2 simultaneously.

[0034] To control the two motors M1 and M2, the control unit S and the common driver D, respectively, add the voltage of the single-phase motor M2 to the third phase W of the three-phase motor M1 at half the amplitude. The fourth phase of the single-phase motor M2 is calculated according to the second phase V of the three-phase motor M1, but with half the voltage of the single-phase motor M2 subtracted, so that the difference between this and the voltage of the second phase V of the three-phase motor M1 yields the motor voltage available for the single-phase motor M2.

[0035] The desired triangular voltages between the motor terminals on the three-phase motor M1 result from the superposition of the phase voltages shifted by 120°:

[0036] The voltage at the single-phase motor M2 results from the difference in voltages at the two connected half-bridges H2, H4 as outputs of a converter:

[0037] The desired voltage and frequency arrive at the single-phase motor M2. Fig. Figure 3 shows, as an example, the voltage curves at the outputs of the four half-bridges H1-H4.

[0038] According to the calculations listed, the sinusoidal waveforms for the two motors M1 and M2 are obtained as follows: Fig. 4. The control curve of the single-phase motor M2 with a different control frequency is clearly visible, as are the three phase curves of the three-phase motor M1, which are shifted by 120° relative to each other.

[0039] The calculated waveforms are provided to the driver stages of the inverter. While the two motors M1 and M2 are running, the currents are measured via the resistors R1-R4, and the voltage levels and phase angles are continuously adjusted by the control unit S using established control methods. This allows the circuit arrangement to be combined with standard control methods. It only needs to be taken into account that the current supplied by the second half-bridge H2 contains components from both motors M1 and M2. Therefore, a correction is made here: I_2=I(Shunt 2)−I(Shunt 4)

[0040] After the correction, the actual current of string 2 of motor M1 is available and is used for the established control procedures.

[0041] An advantage of the circuit design according to the first embodiment is that only the simple peak value of the supply voltage needs to be maintained in the DC link for the single-phase motor M2. The usual superposition of the third harmonic to increase the power of the three-phase motor M1 can be retained. There is no voltage drop due to a coupling capacitor. If the voltage for the single-phase motor M2 is chosen to be sufficiently low, the influence on the design is minimal.

[0042] Fig. Figure 5 shows a circuit diagram of a drive system according to a second embodiment with the three-phase motor M1 and with the single-phase motor M2 on a common half-bridge H4. Fig. Figure 6 shows a time course of the four half-bridge outputs of the circuit diagram of the Fig. 5. Fig. Figure 7 shows a time course of the corresponding calculated sine waveforms of the circuit diagram. Fig. 5 on the two motors M1, M2.

[0043] Here, the single-phase motor M2 is connected between the fourth half-bridge H4 and the star point of the three-phase motor M1. The advantage of this is that both motors M1 and M2 can be operated without restrictions. The entire DC link voltage is available without limitations for the three-phase motor M1, which acts as the main motor. The smaller single-phase motor M2 can be designed with a higher voltage and lower current, which is advantageous in terms of cost.

[0044] The three-phase motor M1 is controlled as is usual with three-phase inverters, i.e., with the corresponding frequency, voltage amplitude, phase angles, and the corresponding superposition of the third harmonic. For the single-phase motor M2, an AC voltage is generated with the frequency, voltage amplitude, and phase angle required for the speed of the three-phase motor M2. This voltage, together with the third harmonic and the DC component of the control signal for the single-phase motor M1, is applied to the fourth half-bridge H4. U4_A(t)=U_+U_3H⋅sin(3⋅ω_M1⋅t)+U_M2⋅sin(ω_M2⋅t)

[0045] The desired triangular voltages between the motor terminals on the three-phase motor M1 result from the superposition of the phase voltages shifted by 120°:

[0046] The voltage at the neutral point results from the three voltages applied to the three phases of the three-phase motor M1, whereby the three phase voltages, which are 120° out of phase, cancel each other out. What remains are the DC component present on all three phases and the third harmonic, which is present on all phases.

[0047] The desired voltage is applied to the single-phase motor M2:

[0048] The presentation of Fig. Figure 6 shows the output voltages of the four half-bridges H1-H4. Half-bridges H1-H3 supply the voltages for the three-phase motor M1, including the superposition of the third harmonic and the DC component. The output of the fourth half-bridge, H4, supplies the voltage for the single-phase motor M2, including the superposition of the third harmonic of the three-phase motor M1 (since this occurs at the star point), as well as a superposition of the DC component.

[0049] The voltages across the two motors M1 and M2, resulting from the above calculations, are the Fig. As can be seen in Figure 7. The three-phase motor M1 receives a sinusoidal three-phase voltage with a 120° phase shift and at the rotational frequency of the three-phase motor M1. The single-phase motor M2 receives a sinusoidal single-phase voltage at the rotational frequency of the single-phase motor M2.

[0050] The current of the single-phase motor M2 is determined via the shunt R4 of the fourth half-bridge H4 and fed to the control unit S. There, established control procedures are performed to adjust the voltage and phase, determine the direction of rotation, and, if necessary, restart the single-phase motor M2.

[0051] For the three-phase motor M1, the first to third half-bridges H1-H3 supply the phase currents. These are superimposed with current components from the single-phase motor M2. Therefore, both the measured phase currents and values ​​corrected for the current through the single-phase motor M2 are taken into account, and the three-phase motor M1 is also operated and controlled using established methods.

[0052] The advantage of the circuit design according to the second embodiment is that there is no voltage drop at all in the three-phase motor M1, and the single-phase motor M2 can be operated with a higher voltage and correspondingly lower current. This allows the use of components with lower current-carrying capacities and smaller conductor cross-sections.

[0053] In both cases, the advantage is that only a comparatively simple circuit with just one half-bridge H4, instead of two half-bridges H4-H5, is required for the single-phase motor M2. The flexible speed control is also advantageous, allowing the speeds of both motors M1 and M2 to be controlled independently. Furthermore, the speed control for the single-phase motor M2 enables a smooth start. The single-phase motor M2 can also be operated on demand, for example, when used with a drain pump that only delivers as much and as fast as necessary, thus saving energy and reducing noise. Depending on the motor used, the direction of rotation can also be determined from the inverter data.

[0054] With a special single-phase motor M2, a start-up in the preferred direction is also conceivable, i.e. the pump delivers better when designed for the preferred direction than with a rotation-direction-independent design, so that the defined direction of rotation can be used for positioning drives. Reference numeral list (part of the description) C smoothing capacitor D driver GL rectifier G-M1 three-phase sine wave generator of M1 three-phase motor G-M2 M2 single phase motor sine wave generator G-H3 H3 generator H1-H5 half-bridges I_2 second phase current through the three-phase motor M1 (phase of the three-phase motor M1 connected to the second half-bridge HL2) Current I(Shunt 2) measured at the measuring resistor R2 of the second half-bridge Current I(Shunt 4) measured at the measuring resistor R4 of the fourth half-bridge L, N voltage input M1 three-phase motor M2 single-phase motor R1-R5 measuring resistors; Shunts S control unit; computer U first phase V second phase Third phase U1_A(t)-U4_A(t) Voltages of the inverter output U_ DC voltage component at the inverter output U_M1 Amplitude of the star or phase voltage of motor M1 U_3H Amplitude of the added third harmonic for power increase U(1-2) (strand) voltage between first half-bridge H1 and second half-bridge H2 U(2-3) (strand) voltage between second half-bridge H2 and third half-bridge H3 U(3-1) (strand) voltage between third half-bridge H3 and first half-bridge H1 U(2-4) (strand) voltage between second half-bridge H2 and fourth half-bridge H4 ω_M1 Angular velocity of the three-phase motor M1 ω_M2 Angular velocity of the single-phase motor M2 t time

Claims

[1] Drive system with a three-phase motor (M1), with a single-phase motor (M2) and with a control circuit with three half-bridges (H1-H3) which are designed and configured to control the three-phase motor (M1), with three measuring resistors (R1-R3), preferably shunts (R1-R3), which are designed and configured to detect the currents of the three half-bridges (H1-H3), with a fourth half-bridge (H4) which is designed and configured to control the single-phase motor (M2), with a fourth measuring resistor (R4), preferably shunt (R4), which is designed and configured to detect the current of the fourth half-bridge (H4), wherein one of the three half-bridges (H1-H3) is designed and configured to control the three-phase motor (M1) and also to control the single-phase motor (M2), and with a control unit (S) which is designed and set up to operate the four half-bridges (H1-H4). [2] Drive system according to claim 1, wherein the control circuit is designed and configured to add half the amplitude of the voltage of the single-phase motor (M2) to the three phases (U, V, W) of the three-phase motor (M1). [3] Drive system according to claim 1 or 2, wherein the control circuit is designed and configured to operate the fourth half-bridge (H4) such that the output voltage of the fourth half-bridge (H4) corresponds to the output voltage of that of the three half-bridges (H1-H3) which additionally drives the single-phase motor (M2), less half the voltage of the single-phase motor (M2). [4] Drive system according to one of the preceding claims, wherein the control circuit is designed and configured to operate the one of the three half-bridges (H1-H3) which additionally controls the single-phase motor (M2) in such a way that the current of this half-bridge (H1-H3) corresponds to the detected current of the corresponding measuring resistor (R1-R3) less the detected current of the measuring resistor (R4) of the fourth half-bridge (H4). [5] Drive system according to claim 1, wherein the three phases (U, V, W) of the three-phase motor (M1) are connected to a star point, wherein the single-phase motor (M2) is arranged between the fourth half-bridge (H4) and the star point of the three-phase motor (M1). [6] Drive system according to one of the preceding claims, wherein the three-phase motor (M1) is a three-phase AC motor (M1), preferably a three-phase synchronous motor (M1). [7] Drive system according to one of the preceding claims, wherein the single-phase motor (M2) is a single-phase AC motor (M2), preferably a single-phase synchronous motor (M2). [8] Household appliance, preferably washing machine or dishwasher, with at least one drive system according to any of the preceding claims.

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