Method for reducing thermal stress of a power semiconductor switch, an electrical converter unit and an elevator

Abstract

An electric converter unit and a method for reducing thermal stress of a power semiconductor switch, such as an IGBT, of an electric converter unit, the electric converter unit comprising at least a gate control circuit, wherein the electric converter unit controls an electric motor. The method comprises determining a load and estimating a required motor current based on the determined load and / or a predetermined speed profile. The electric converter unit has at least a first operating state and a second operating state. If a predetermined criterion is fulfilled, the second operating state is used, the predetermined criterion relating to at least one of: the estimated required current, a measured motor speed, a temperature of the power semiconductor switch and / or the electric converter unit, a temperature model of the power semiconductor switch and / or the electric converter unit. In the second operating state, a lower switching frequency of the power semiconductor switch is used than in the first operating state, and in the second operating state, a higher switching speed of the power semiconductor switch is used than in the first operating state.

Description

TECHNICAL FIELD

[0001] The present invention relates generally to power semiconductor switches, such as IGBTs. In particular, but not exclusively, the present invention relates to reducing thermal stress of power semiconductor switches. BACKGROUND

[0002] Electric converter units and control systems are used to control electric motors. These units and control systems are used to control motor speed and torque by, for example, changing the motor input frequency and voltage. There are different requirements for electric converter units and control systems in different types of environments.

[0003] An elevator environment, for example, is characterized by a high required current during acceleration relative to the required current at the rated speed. In an elevator environment, it is desirable that the acceleration proceeds smoothly. In this case, at the beginning of the acceleration, the phase current of the motor is concentrated mainly on one switch of the inverter bridge. The concentration of the current causes a large change in the temperature of the terminal of that particular switch. With the change in the terminal temperature, the difference in the coefficient of thermal expansion causes mechanical stress on the material interface of the device. The mechanical stress eventually leads to a stress fracture in the interface.

[0004] The above-mentioned problem is most severe in an elevator environment when the elevator car is fully loaded and being lifted. If the travel height during the drive is also kept short, the duration of the acceleration current is longer than the current during the rated drive.

[0005] The magnitude of the electromagnetic interference (EMI) caused by the inverter is related to the switching frequency and the switching speed at which the power semiconductors are turned on. To minimize the losses, the semiconductors should be controlled with a low switching frequency and a high switching speed. A low switching frequency has a positive effect on EMI, but a negative effect on the noise produced by the motor. A high switching speed has a negative effect on the EMI produced by the system.

[0006] There are known solutions for reducing the thermal stress effects of power semiconductor switches. In prior art systems, the stress caused by thermal cycling is reduced by designing the size of the semiconductors so that they can withstand a certain amount of acceleration. This solution based on size design is simple, but the larger the semiconductor, the greater the switching losses of the semiconductor. In bipolar devices, such as IGBTs, the connection voltage remains the same, and the main resistance part decreases. Thus, simply put, with this solution, the losses remain essentially similar, but are distributed to a larger area. The problem with this solution is that increasing the area of the semiconductor also increases the price of the device.

[0007] According to another known solution, the switching frequency can also be changed so that at low motor speeds, i.e. at the beginning of acceleration and at the end of deceleration, a smaller switching frequency is used, while in other cases the switching frequency is higher. The problem with this approach is that the change in switching frequency can be easily sensed. The lower the switching frequency, the greater the perceived noise disturbance. SUMMARY

[0008] The object of the present application is to provide a solution for reducing thermal stress of power semiconductors.

[0009] The object of the present application is achieved by a method for reducing thermal stress of power semiconductor switches of an electrical converter unit, an electrical converter and an elevator unit.

[0010] Unlike the prior art solutions, in the solution of the present application, the temperature variation in the semiconductor switch, such as an IGBT, is reduced by reducing the losses of the semiconductor switch based on predetermined criteria. In this way, the temperature variation reducing function of the semiconductor switch can be activated only when needed.

[0011] According to a first aspect, a method for reducing thermal stress of power semiconductors, such as IGBTs, is provided. The method comprises determining a load and estimating a required motor current based on the determined load and / or a predetermined speed profile. The electrical converter unit has at least a first operating state and a second operating state, wherein the second operating state is used if a predetermined criterion is met, the predetermined criterion relating to at least one of the following: the estimated required current, a measured motor speed, a temperature of the power semiconductor switch and / or the electrical converter unit, a temperature model of the power semiconductor switch and / or the electrical converter unit. In the second operating state, a lower switching frequency of the power semiconductor switch is used than in the first operating state, and in the second operating state, a higher switching speed of the power semiconductor switch is used than in the first operating state.

[0012] According to a second aspect, an electrical converter unit is provided. The electrical converter unit is configured to perform at least the method according to the first aspect or any embodiment thereof.

[0013] Hence, the electrical converter unit can comprise at least a power semiconductor switch, e.g. an IGBT, and a gate control circuit, wherein the electrical converter unit is configured to determine a load, and to estimate a required motor current based on the determined load and / or a predetermined speed profile. The electrical converter unit has at least a first operating state and a second operating state. The electrical converter unit is configured to use the second operating state if a predetermined criterion is fulfilled, which relates to at least one of: the estimated required current, a measured motor speed, a temperature of the power semiconductor switch and / or the electrical converter unit, a temperature model of the power semiconductor switch and / or the electrical converter unit. The electrical converter unit is configured to use a lower switching frequency of the power semiconductor switch in the second operating state than in the first operating state, and to use a higher switching speed of the power semiconductor switch in the second operating state than in the first operating state.

[0014] According to a third aspect, an elevator is provided. The elevator comprises an elevator car, an elevator motor configured to move the elevator car, an electrical converter unit for operating the elevator motor, and a control unit configured to perform at least the method according to the first aspect or any embodiment thereof.

[0015] In various embodiments, the electrical converter unit can comprise a converter device, e.g. a frequency converter or an inverter.

[0016] In one embodiment of the invention, the second operating state is used if the motor speed is below a certain predetermined threshold value and the estimated required current value is above a certain predetermined threshold value.

[0017] In one embodiment of the invention, the internal temperature of the power semiconductor switch and / or the electrical converter unit is measured and / or simulated, and the operating state is changed from the first state to the second state if, in addition to reaching a predetermined motor speed and a predetermined estimated required current value, a certain measured and / or simulated temperature threshold limit is reached.

[0018] In one embodiment of the invention, the internal temperature of the power semiconductor switch and / or the electrical converter unit is measured and / or simulated, and the operating state is changed from the first state to the second state only when a certain measured and / or simulated temperature threshold limit is reached, regardless of the motor speed and the estimated required current value.

[0019] In one embodiment of the invention, the operating state is changed from the first state to the second state when the drive starts, preferably at a high load, and the motor speed is low, and / or when the motor is decelerating and the motor speed is low. For example, the operating state can be changed from the first state to the second state when the drive starts at a load above a predetermined load value, and the motor speed is lower or below a predetermined speed, and / or when the motor is decelerating and the motor speed is lower or below a predetermined speed.

[0020] In one embodiment of the invention, the electrical converter unit comprises a first gate resistance value, a second gate resistance value and means for switching between the first gate resistance value and the second gate resistance value, wherein the first gate resistance value is higher than the second gate resistance value.

[0021] In one embodiment of the invention, the switching speed of the power semiconductor switch is increased by using a lower gate resistance value of the power semiconductor switch.

[0022] In one embodiment of the invention, the second resistance value is used for the second operating state and the first resistance value is used for the first state.

[0023] In one embodiment of the invention, the electrical converter unit comprises a first gate control voltage, a second gate control voltage and means for switching between the first gate control voltage and the second gate control voltage, wherein the first gate control voltage is lower than the second gate control voltage.

[0024] In one embodiment of the invention, the switching speed of the power semiconductor switch is increased by increasing the gate control voltage of the power semiconductor switch.

[0025] In one embodiment of the invention, the first gate control voltage is used for the first operating state and the second gate control voltage is used for the second operating state.

[0026] In one embodiment of the invention, the electrical motor is an elevator motor of an elevator.

[0027] In various embodiments, the electrical motor can be one of the following: synchronous reluctance motor, permanent magnet motor, permanent magnet linear motor, permanent magnet assisted synchronous reluctance motor, linear switched reluctance motor.

[0028] The invention provides advantages over prior art solutions. With the solution of the invention, a significant reduction in the thermal cycling amplitude can be achieved. Reducing the switching frequency while compensating for the increased EMI level by higher switching speed.

[0029] If the selection of the operating mode with reduced thermal stress is to rely only on the measurement of the current and the speed of the motor, the semiconductor device can generate losses and heat up at the beginning of the acceleration before the appropriate operating mode with reduced thermal stress can be selected. For this reason, it is advantageous to predict the acceleration and / or deceleration and to select the operating mode based at least partly on the predicted acceleration, deceleration and / or the required motor current.

[0030] In addition to elevators, the method of the present application can be used in different cyclical applications. The method of the present application can also be used, for example, to widen the operating temperature range of a frequency converter, for example by adding an internal temperature measurement and / or temperature model of a power semiconductor switch, for example an IGBT, to the frequency converter logic used for the overheat protection of the frequency converter. According to some embodiments of the present application, the decision to use the temperature stress reduction function, i.e. the second operating mode, can in some applications be based on the temperature measurement and / or temperature model only. Examples of such applications are pumps and blowers.

[0031] In addition, the elevator ambient temperature measurement and / or the estimated temperature of the temperature model of the switch, for example the IGBT chip temperature, can be used in some embodiments of the present application. For example, when the temperature of the operating environment is low, it can not be necessary to reduce the temperature stress if the estimation of the chip temperature will remain low.

[0032] Various other advantages will become clear to the skilled person on the basis of the following detailed description.

[0033] The expression "several" can herein mean any positive integer starting from one (1), i.e. at least one.

[0034] The expression "several" can herein mean any positive integer starting from one (1), i.e. at least one.

[0035] The terms "first", "second" and "third" are used herein to distinguish one element from another, and not for the purpose of particular prioritization or ordering, unless explicitly stated otherwise.

[0036] The exemplary embodiments of the present application presented herein are not to be construed as limitations on the applicability of the appended claims. The verb "comprise", used in this document, is used as an open limitation that does not exclude the existence of also unrecited features. The features recited in the dependent claims are mutually freely combinable unless otherwise explicitly stated.

[0037] The novel features considered characteristic of the present application are set forth in the appended claims. The application itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of the specific embodiments when read in connection with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0038] In the drawings, some embodiments of the present application are shown by way of example and not limitation.

[0039] Figures 1A-1C An electric converter unit according to some embodiments of the present application is schematically shown.

[0040] Figure 2An exemplary implementation of certain parts of an electrical converter unit according to embodiments of the application is schematically illustrated.

[0041] Figure 3 An elevator according to embodiments of the application is schematically illustrated.

[0042] Figure 4 An elevator according to embodiments of the application is schematically illustrated.

[0043] Figure 5A and 5B Exemplary embodiments of how to change operating modes in an elevator environment are presented.

[0044] Figure 6A and 6B An exemplary implementation of certain parts of an electrical converter unit according to some embodiments of the application is schematically illustrated. DETAILED DESCRIPTION

[0045] Figure 1A An electrical converter unit 14 according to embodiments of the application is schematically illustrated. The electrical converter unit 14 can comprise a frequency converter or inverter, or in particular, a power conversion circuit 14B thereof. Furthermore, the electrical converter unit 14 can comprise a current determination device 14C and / or a voltage determination device (not shown) for determining a current, e.g. three instantaneous phase currents, flowing into or out of the electrical motor 12, or a voltage existing between the motor phases or between a motor phase and a ground / reference / neutral potential, e.g. the star point of the motor 12, respectively. Preferably, the current determination device 14C and / or the voltage determination device can be arranged in conjunction with a control unit 14A for providing information about said currents / voltages to the control unit 14A. Preferably, the electrical converter unit 14 can be configured to control said currents / voltages at least in normal operating conditions for controlling the operation of the motor 12, e.g. the rotation or movement of the rotor of the motor 12.

[0046] Furthermore, the electrical converter unit 14 can comprise a control unit 14A arranged in close proximity to the converter device 14D, e.g. a frequency converter or inverter, including a power conversion circuit 14B thereof, e.g. arranged within the same housing. There can also be external connections 15 arranged to the electrical converter unit 14 for providing e.g. measurements, control signals and / or power from an external system connected to the electrical converter unit 14, or in particular, to its control unit 14A. The external system can be e.g. a vehicle, an industrial process or an elevator, as Figure 3 and Figure 4 shown.

[0047] Figure 1B An electrical converter unit 14 according to embodiments of the application is schematically illustrated. Figure 1BThe electrical converter unit 14 in Fig. 1 is otherwise similar to the electrical converter unit 14 shown and described in Figure 1A Fig. 1, except that the control unit 14A is arranged separately in relation to the converter device 14D, e.g. outside its housing. Thus, the control unit 14A can be arranged to be connected only with the conversion circuit 14B. The control unit 14A can be part of a control unit of an external system comprising the electrical converter unit 14, for example.

[0048] Figure 1C An electrical converter unit 14 according to an embodiment of the application is shown schematically. In Figure 1C Fig. 1, the electrical converter unit 14 can comprise a frequency converter with an energy storage 24, e.g. a capacitor (bank) or a battery, arranged to the intermediate circuit 23, or in the case of a battery at least connected with the intermediate circuit 23. The frequency converter can be arranged to supply power between the power grid 20 and the electrical motor 12. The frequency converter can comprise a load bridge 22 connected to the electrical motor 12 for supplying power between the electrical motor 12 and the load bridge 22. The load bridge 22 can comprise controllable solid state switches, e.g. power conversion circuits forming a three-phase two- or three-level inverter. The supply voltage of the electrical motor 12 can be formed by controlling the solid state switches of the load bridge 22 with a control unit 14A of the frequency converter, e.g. with a pulse width modulation (PWM) technique. The frequency converter can comprise current 14C and / or voltage determining means, e.g. current or voltage sensors, which can be arranged in connection with the supply cables of the stator windings of the motor 12 for measuring the stator current and / or voltage.

[0049] The electrical converter unit 14 described above with reference to Figures 1A-1C Fig. 1 can be configured to control the operation of the electrical motor 12, e.g. by a field oriented control or vector control method known to the skilled person.

[0050] In various embodiments of the application, the electrical converter unit 14 shown and described in connection with any one of the figures, or specifically its control unit 14A, can be configured to perform at least one embodiment of the method according to the application. Figures 1A-1C

[0051] Thus, in various embodiments, the control unit 14A can comprise at least a processing unit, e.g. a processor or a microcontroller, for performing calculations and / or executing computer program code, for example, and a memory for storing such code, measurement data, etc.

[0052] In various embodiments, the electrical motor 12 can be one of the following: a synchronous reluctance motor, a permanent magnet motor, a permanent magnet linear motor, a permanent magnet assisted synchronous reluctance motor, a linear switched reluctance motor.

[0053] ​The converter unit 14 can comprise a converter device 14D, e.g. a frequency converter or an inverter, e.g. comprising solid state semiconductor switches. Figure 2 An exemplary implementation of a controllable solid state switch of a load bridge is schematically illustrated. The switch can be, for example, an insulated gate bipolar transistor (IGBT) or a silicon carbide junction field effect transistor. In one embodiment, the control unit of the load bridge 22 (see Figure 1C ) of the electric converter unit 14 controls the solid state switch of the load bridge, e.g. according to the solution of the present application, wherein the first and second operating states are used. Figure 2 The load bridge of the electric converter unit 14 is a load bridge of a two-level converter. The present application is not limited to two-level converters only, but can also be applied to converters of higher voltage levels.

[0054] The load bridge (inverter) is configured to invert an intermediate circuit DC voltage to, for example, a variable frequency three-phase AC voltage. The frequency converter can power, for example, a three-phase AC motor. The inverter can comprise, for example, six diodes D1, D3, D5, D7, D9, D11 and six IGBTs: Q1, Q3, Q5, Q7, Q9, Q11, as Figure 2 illustrated in the example of Fig. 1. The inverter connects each motor phase to the negative or positive pole of the DC bus in a certain order. By adjusting the width and number of voltage pulses, for example, a desired amplitude and frequency of the AC voltage supplied to the motor can be achieved.

[0055] As mentioned earlier, a feature, for example, in an elevator environment is that the required current during acceleration is higher with respect to the required current at the rated speed. In this case, at the beginning of the acceleration, the phase current of the motor is concentrated mainly on one switch of the inverter bridge. The concentration of the current causes a large change in the temperature of the terminals of that particular switch. With the change in the temperature of the terminals, the difference in the coefficient of thermal expansion can cause mechanical stress to the material interfaces of the devices. The mechanical stress can eventually lead to a stress fracture of the interfaces. With the help of the present application, the stress on these devices can be reduced.

[0056] Figure 3 An elevator 100 according to an embodiment of the present application is schematically illustrated. The elevator 100 can comprise an elevator car 10 coupled to a counterweight 17 via a rope 19, a belt or the like. The rope 19 or the like can travel around a drive pulley 18, an electric motor 12 being configured to generate a force into the drive pulley 18 for moving the elevator car 10 in response to operation of the electric motor 12. In particular, the elevator car 10 can be arranged to move in response to movement, e.g. rotation, of a rotor 11 of the motor 12.

[0057] At least one elevator brake 16, i.e. one, two or several, can be arranged so that when controlled by de-energization, it is configured to meet the drive pulley 18 and in this way brake the movement of the motor 12, in particular the movement of its rotor 11, and thus the elevator car 10, or keep the elevator car 10 stationary in the hoistway. When the brake 16 is energized, the brake 16 opens, allowing the elevator car 10 to move. Alternatively, the elevator 100 can be implemented without a counterweight 17. Alternatively, the motor 12 can be in the form of a linear motor, which has a stator extending along the elevator hoistway and a rotor or "thruster" coupled to the elevator car 10, as shown in Figure 4

[0058] The elevator 100 can comprise an elevator control unit 1000 for controlling the operation of the elevator 100. The elevator control unit 1000 can be a separate device or can be included in other components of the elevator 100, for example in the electric drive 14 or as part of the electric drive 14. The elevator control unit 1000 can also be implemented in a distributed manner, so that for example a part of the elevator control unit 1000 can be included in the electric drive 14, for example in its control unit 14A, while another part is included in the elevator car 10. The elevator control unit 1000 can also be arranged in more than two locations or more than two devices in a distributed manner.

[0059] The elevator control unit 1000 and / or the control unit 14A can comprise one or more processors, one or more volatile or non-volatile memories for storing parts of computer program code and any data values, and can comprise one or more user interface units. The mentioned elements can be communicatively coupled with each other with, for example, internal buses.

[0060] The processor of the elevator control unit 1000 and / or the control unit 14A can be configured at least to implement at least some of the method steps of the present application. The implementation of the method can be implemented by arranging the processor to execute at least some part of the computer program code stored in the memory, which computer program code causes the processor and thus the elevator control unit 1000 and / or the control unit 14A to implement one or more method steps of the present application. Thus, the processor can be arranged to access the memory and retrieve and store any information from and to the memory. For the sake of clarity, the processor herein refers to any unit adapted to process information and control the operation of the elevator control unit 1000 and / or the control unit 14A and other tasks. The operations can also be implemented with a microcontroller solution with embedded software. Similarly, the memory is not limited to a specific type of memory, but any memory type suitable for storing the described pieces of information can be applied in the context of the present application. ​

[0061] Figure 4 An elevator 100 according to an embodiment of the present invention is schematically illustrated. The elevator 100 may include at least one or more elevator cars 10 that move within an elevator shaft 13 or an elevator car path 13. The elevator car 10 may include an electrical converter unit 14, such as a converter device 14D, such as a frequency converter or inverter, and / or a second energy storage device, such as one or more batteries. The electrical converter unit 14 can be used to operate a thruster 11 disposed on the elevator car 10 to move the car 10 along the elevator shaft 13. Other electrically operated devices, such as lighting, doors, user interfaces, emergency rescue devices, etc., may also be present in the elevator car 10. The electrical converter unit 14 or other converters, such as inverters or rectifiers, may be used to operate one or more of the other devices of the elevator car 10. Preferably, the second energy storage device may be electrically connected to the electrical converter unit 14, for example, electrically connected to its intermediate circuit 23, for providing power to the electrical converter unit 14 and / or for storing power provided by the electrical converter unit 14 or another converter or other power source. Elevator 100 may preferably include elevator control unit 1100 and / or control unit 14A, for example, in combination with Figure 3 The control unit described or a similar control unit.

[0062] One or more actuators 11 may be connected to one or each of the elevator cars 10. The number of actuators 11 may vary depending on the structure of the linear motor 12, such as the number of stator beams 12A.

[0063] Preferably, the elevator 100 may include at least two floors having floor doors 25 or openings 25. The elevator car 10 may also include doors. Although in Figure 4 The image shows vertically aligned floor stations with two horizontally separated groups or "columns," but there can also be only one column as in a traditional elevator, or more than two columns, such as three columns.

[0064] Regarding the elevator shaft 13, it can be, for example, defining a substantially enclosed volume in which the elevator car 10 is adapted and configured to move. The walls can be, for example, concrete, metal, or at least partially glass, or any combination thereof. In this document, the elevator shaft 13 essentially refers to any structure or path along which the elevator car 10 is configured to move.

[0065] from Figure 4 As can be seen from this, regarding the multi-car elevator 100, one or more elevator cars 10 can move vertically and / or horizontally along the elevator shaft 13 according to the direction of the stator beam 12A. This is similar to... Figure 3In an embodiment of the present application, one or more elevator cars 10 can be configured to move along several vertical and / or horizontal stator beams, for example, as Figure 4 The stator beam 12A is part of a linear electric motor of the elevator 100 for moving one or more elevator cars 10 in the elevator shaft 13. The stator beam 12A can preferably be arranged in a fixed manner, i.e. fixed with respect to the elevator shaft 13, for example by fastening parts to the wall of the shaft, which can be arranged rotatable at the change of position in the direction of the elevator car 10.

[0066] In the solution of the present application, the thermal stress of the power semiconductor switches, e.g. IGBTs, of the electric converter unit is reduced. In the solution of the present application, the load is measured or determined and based on the measured or determined load and / or a predetermined speed profile, the required motor current is estimated. The electric converter unit has at least a first operating state and a second operating state. The second operating state is used if a predetermined criterion is met, which relates to at least one of the following: the estimated required current, the measured motor speed, the temperature of the power semiconductor switches and / or the electric converter unit, a temperature model of the power semiconductor switches and / or the electric converter unit. In the second operating state, a lower switching frequency of the power semiconductor switches is used than in the first operating state, and in the second operating state, a higher switching speed of the power semiconductor switches is used than in the first operating state.

[0067] For example, the second operating state can be used if the motor speed is below a certain predetermined threshold value and the estimated required current value is above a certain predetermined threshold value. In an embodiment of the present application, the operating state is changed from the first state to the second state when starting the drive with a higher load and the motor speed is low and / or when the motor is decelerating and the motor speed is low and the load is high. In this case, the phase current of the motor is mainly concentrated on one switch of the inverter bridge because the motor speed is low.

[0068] In an embodiment of the present application, the switching speed of the power semiconductor switches is increased by using a lower gate resistance value of the power semiconductor switches. In an embodiment of the present application, the electric converter unit comprises a first gate resistance value, a second gate resistance value and means for switching between the first gate resistance value and the second gate resistance value, wherein the first gate resistance value is higher than the second gate resistance value. In an embodiment of the present application, the second resistance value is used for the second operating state and the first resistance value is used for the first state.

[0069] In one embodiment of the application, the switching speed of the power semiconductor switch is increased by increasing the gate control voltage of the power semiconductor switch. In one embodiment of the application, the electrical converter unit comprises a first gate control voltage, a second gate control voltage and means for switching between the first gate control voltage and the second gate control voltage, wherein the first gate control voltage is lower than the second gate control voltage. In one embodiment of the application, the first gate control voltage is used for the first operating state and the second gate control voltage is used for the second operating state.

[0070] In the solution of the application, the load can be determined directly or indirectly. The load can be determined, for example, by a scale in the elevator car, in the rope and / or in connection with the attachment points of the rope. In addition, a weight sensor can be used to determine the load. In one embodiment of the application, the load determination can be based on the motor torque, for example, when the elevator car remains stable after the release of the brake.

[0071] In one embodiment of the application, the internal temperature of the power semiconductor switch and / or the electrical converter unit is measured and / or simulated, and the operating state is changed from the first state to the second state if, in addition to reaching a predetermined motor speed and a predetermined estimated required current value, a certain measured and / or simulated temperature threshold limit is also reached. The operating state can change back from the second state to the first state when the temperature is below the temperature threshold limit.

[0072] In one embodiment of the application, the internal temperature of the power semiconductor switch and / or the electrical converter unit is measured and / or simulated, and the operating state is changed from the first state to the second state only when a certain measured and / or simulated temperature threshold limit is reached, regardless of the motor speed and the estimated required current value. The operating state can change back from the second state to the first state when the temperature is below the temperature threshold limit.

[0073] In one embodiment of the application, the temperature determination can be used as a criterion for changing the operating mode between the first operating mode and the second operating mode. In one embodiment, the steps of determining the load and estimating the required motor current on the basis of the determined load and / or a predetermined speed profile are not necessarily performed. In this embodiment, for example, the operating state can change to the second operating state if the temperature (measured and / or simulated) is above a certain temperature limit. In this case, the second operating mode can be used, for example, when the motor speed is low. If the motor speed is low, but the temperature does not exceed the predetermined limit, the system can operate in the first operating state, as the temperature stress does not require a change in the operating mode.

[0074] Figure 5A and 5BAn example is presented of how the operating mode can be changed in an elevator environment and which information can be utilized when selecting the operating mode. In this example, an elevator with a counterweight is used as the elevator. In these figures, the motor speed during elevator movement is shown at the top of the figure, as well as a threshold level at which the temperature stress on the semiconductor switches can become a problem if high current is required. Below the motor speed graph, the required current level is shown with a threshold current level, which is the minimum current level that can cause stress on the semiconductor switches, especially when the motor speed is also low. The next two graphs present at which moment the motor speed is below the threshold and at which moment the required current is above the threshold. The last three graphs present which operating state is used, whether a higher or lower gate resistance value is used, and whether a higher or lower switching frequency is used.

[0075] Figure 5A An example is presented of how the operating mode can be changed in an elevator environment and which information can be utilized when selecting the operating mode. In this example, an elevator with a counterweight is used as the elevator. In these figures, the motor speed during elevator movement is shown at the top of the figure, as well as a threshold level at which the temperature stress on the semiconductor switches can become a problem if high current is required. Below the motor speed graph, the required current level is shown with a threshold current level, which is the minimum current level that can cause stress on the semiconductor switches, especially when the motor speed is also low. The next two graphs present at which moment the motor speed is below the threshold and at which moment the required current is above the threshold. The last three graphs present which operating state is used, whether a higher or lower gate resistance value is used, and whether a higher or lower switching frequency is used.

[0076] Figure 5B An example is presented of how the operating mode can be changed in an elevator environment and which information can be utilized when selecting the operating mode. In this example, an elevator with a counterweight is used as the elevator. In these figures, the motor speed during elevator movement is shown at the top of the figure, as well as a threshold level at which the temperature stress on the semiconductor switches can become a problem if high current is required. Below the motor speed graph, the required current level is shown with a threshold current level, which is the minimum current level that can cause stress on the semiconductor switches, especially when the motor speed is also low. The next two graphs present at which moment the motor speed is below the threshold and at which moment the required current is above the threshold. The last three graphs present which operating state is used, whether a higher or lower gate resistance value is used, and whether a higher or lower switching frequency is used.

[0077] In one embodiment of the invention, the change from the first operating state to the second operating state can be made when the estimated required current is above a predetermined threshold limit and / or the motor speed is zero or below a certain threshold. This is the case, for example, when the motor speed starts to accelerate from zero, for example when a fully loaded elevator car starts to be hoisted.

[0078] In one embodiment of the application, the change from the first operating state to the second operating state can be made when the motor speed is decelerated and the motor speed is reduced below a certain threshold value and the estimated required current exceeds a certain predetermined threshold limit. This is for example the case when the motor has to brake and decelerate an empty elevator.

[0079] In one embodiment of the application, the change from the first operating state to the second operating state can be made based on the measured temperature and / or an estimated temperature based on a temperature model if the temperature exceeds a certain threshold level. In this case, the estimated required motor current and / or motor speed can be used as additional criteria. In this case, the operating state is changed only if the estimated required motor current, motor speed and temperature meet the criteria required for changing the state. In one embodiment of the application, the operating state can be changed based on the temperature only, for example, without considering other criteria such as the estimated required current and motor speed.

[0080] In one embodiment of the application, the change from the second operating state to the first operating state can be made when the motor speed exceeds a certain predetermined threshold limit. This is for example the case when the motor speed is increased to a certain speed, for example when the elevator reaches a certain speed.

[0081] In one embodiment of the application, the first operating state can be used even if the motor speed is zero or below a certain threshold value when the estimated required current is below a certain threshold value. This is for example the case if the motor load remains low, for example if an empty elevator car is lifted.

[0082] In one embodiment of the application, the change from the second operating state to the first operating state can be made based on the measured temperature and / or an estimated temperature based on a temperature model if the temperature is below a certain threshold level. In this case, the estimated required motor current and / or motor speed can be used as additional criteria. In this case, the operating state is changed only if the estimated required motor current, motor speed and temperature meet the criteria required for changing the state. In one embodiment of the application, the operating state can be changed based on the temperature only, for example, without considering other criteria such as the estimated required current and motor speed.

[0083] The solution of the application can be implemented in many different ways in the electrical converter unit. Figure 6A and 6B The drive circuit of the electrical converter unit is schematically shown as an example implementation embodiment.

[0084] In Figure 6AIn an example embodiment, the reduced switching time of the IGBT Q1 is achieved by using a field effect transistor Q2, the drain of which is connected to the first pole of the turn-off gate resistor R2. The source of the field effect transistor Q2 is connected to the gate G of the IGBT Q1 to be controlled. The second pole of the turn-off gate resistor R2 is connected to the output U1 of the main gate controller. The gate of the field effect transistor Q2 is connected to the output U2 of a separate auxiliary gate controller. A discharge resistor R3 can be connected between the gate and the source of the field effect transistor Q2. A discharge resistor R4 can be connected between the auxiliary emitter and the gate of the IGBT to be controlled. The current output capability of the auxiliary emitter is determined based on the field effect transistor Q2 for which the turn-on requires only a comparably low current.

[0085] In this example, the separate two-level control voltage, e.g. +15V / -15V, can be generated in a conventional way by rectifying a dc square wave with a diode bridge BR1. The rectified voltage can be filtered by capacitors C1 and C2, the center poles of which are grounded to the auxiliary emitter AE of the IGBT to be controlled.

[0086] When the CTRL_ON signal is active and the 2ND_OPER_STATE_ON is inactive, the +15V control voltage is directed to the gate of the IGBT via the gate resistor R1. When the CTRL_ON signal is active and the 2ND_OPER_STATE_ON is active, the +15V control voltage is directed to the gate of the IGBT via the series connection of the gate resistor R1 and the auxiliary gate resistor R2 and the field effect transistor Q2 in parallel with the gate resistor R1. Thus, the current supplied from the output U1 of the main gate controller is distributed between the gate resistor R1 and the auxiliary gate resistor R2.

[0087] When the IGBT Q1 is controlled to turn off, the CTRL_ON signal is inactive and the 2ND_OPER_STATE_ON signal is inactive, the gate charge is discharged via the gate resistor R1, the parasitic diode of the field effect transistor Q2 and the auxiliary gate resistor R2. When the CTRL_ON signal is inactive and the 2ND_OPER_STATE_ON is active, the gate charge of the IGBT is discharged via the gate resistor R1, the auxiliary gate resistor R2 and the open channel of the field effect transistor Q2.

[0088] The control signals CTRL_ON and 2ND_OPER_STATE_ON can be at the voltage potential of the control voltage. The 2ND_OPER_STATE_ON can be adjusted individually for each switch of the inverter and / or simultaneously for all switches. The CTRL_ON control signal is an individual signal for each switch of the inverter.

[0089] Figure 6B The example embodiment is otherwise similar to the previous example, but an adjustable DC-DC converter PSU1 is added to the circuit, in this case a higher level control system can change the control voltage instruction with CTRL_UGE control signal. The DC-DC converter PSU1 adjusts and regulates the two-stage control voltage based on the instruction it receives.

[0090] The control voltage level regulation features described herein in relation to Figure 6B may be implemented without the optional gate resistor values of the previous examples, or can be implemented as an addition to the solution with optional gate resistor values, for example as shown in Figure 6A .

[0091] The specific examples provided in the description given above should not be construed as limiting the applicability and / or interpretation of the claims that follow. The lists and groups of examples provided in the description given above are not exhaustive, unless explicitly stated otherwise.

Claims

1. A method for reducing thermal stress of a power semiconductor switch of an electrical converter cell (14), the electrical converter cell (14) comprising at least a gate control circuit, wherein, The electrical converter unit (14) controls an electrical motor (12), characterized in that the method comprises: - determining a load, - estimating a required motor current based on the determined load and / or a predetermined speed profile, - wherein the electrical converter unit (14) has at least a first operating state and a second operating state, - wherein the second operating state is used if a predetermined criterion is fulfilled, the predetermined criterion relating to at least one of: the estimated required current, a measured motor speed, a temperature of the power semiconductor switches and / or the electrical converter unit, a temperature model of the power semiconductor switches and / or the electrical converter unit (14), - wherein the operating state is changed from the first operating state to the second operating state when the drive is started with a load above a predetermined load value and the motor speed is below a predetermined speed, and / or when the motor is decelerating and the speed of the motor is below a certain predetermined speed, - wherein in the second operating state a lower switching frequency of the power semiconductor switches is used than in the first operating state, and in the second operating state a higher switching speed of the power semiconductor switches is used than in the first operating state.

2. The method of claim 1, wherein, The second operating state is used if the motor speed is below a certain predetermined threshold value and the estimated required current value is above a certain predetermined threshold value.

3. The method of claim 2, wherein, The internal temperature of the power semiconductor switches and / or the electrical converter unit (14) is measured and / or simulated and the operating state is changed from the first operating state to the second operating state if, in addition to reaching a predetermined motor speed and a predetermined estimated required current value, a certain measured and / or simulated temperature threshold limit is reached.

4. The method of claim 1, wherein, The internal temperature of the power semiconductor switches and / or the electrical converter unit (14) is measured and / or simulated and the operating state is changed from the first operating state to the second operating state only when a certain measured and / or simulated temperature threshold limit is reached, regardless of the motor speed and the estimated required current value.

5. The method according to any of the preceding claims, characterized in that, The electrical converter unit comprises a first gate resistance value, a second gate resistance value and means for switching between the first gate resistance value and the second gate resistance value, wherein the first gate resistance value is higher than the second gate resistance value.

6. The method according to any one of claims 1 to 5, characterized in that, The switching speed of the power semiconductor switches is increased by using a lower gate resistance value of the power semiconductor switches.

7. The method of claim 5, wherein, The second gate resistance value is used for the second operating state and the first gate resistance value is used for the first operating state.

8. The method according to any one of claims 1 to 5, characterized in that, The electrical converter unit comprises a first gate control voltage, a second gate control voltage and means for switching between the first gate control voltage and the second gate control voltage, wherein the first gate control voltage is lower than the second gate control voltage.

9. The method according to any one of claims 1 to 5, characterized in that, The switching speed of the power semiconductor switches is increased by increasing the gate control voltage of the power semiconductor switches.

10. The method of claim 8, wherein, The first gate control voltage is used for the first operating state and the second gate control voltage is used for the second operating state.

11. The method according to any one of claims 1 to 5, characterized in that, The electrical motor (12) is an elevator motor (12) of an elevator (100).

12. The method according to any one of claims 1 to 5, characterized in that, The electric motor (12) is one of the following: a synchronous reluctance motor, a permanent magnet motor, a permanent magnet linear motor, a permanent magnet assisted synchronous reluctance motor, a linear switched reluctance motor.

13. An electric converter cell (14) comprising at least a power semiconductor switch and a gate control circuit, wherein The electric converter unit (14) is configured to control the electric motor (12), characterized in that the electric converter unit is configured to: - determine a load, - estimate a required motor current based on the determined load and / or a predetermined speed profile, - wherein the electric converter unit (14) has at least a first operating state and a second operating state, - wherein the electric converter unit (14) is configured to use the second operating state if a predetermined criterion is met, the predetermined criterion relating to at least one of: the estimated required current, a measured motor speed, a temperature of the power semiconductor switches and / or electric converter unit, a temperature model of the power semiconductor switches and / or electric converter unit (14), - wherein the electric converter unit (14) changes operating state from the first operating state to the second operating state when starting driving with a load above a predetermined load value and the motor speed is below a predetermined speed, and / or when the motor is decelerating and the motor speed is below a predetermined speed, - wherein the electric converter unit (14) is configured to, in the second operating state, use a lower switching frequency of the power semiconductor switches than in the first operating state, and in the second operating state, use a higher switching speed of the power semiconductor switches than in the first operating state.

14. The electrical converter cell (14) according to claim 13, characterized in that The electric converter unit (14) is configured to use the second operating state if the motor speed is below a certain predetermined threshold value and the estimated required current value is above a certain predetermined threshold value.

15. The electrical converter cell (14) according to claim 14, characterized in that The electric converter unit (14) is configured to measure and / or simulate an internal temperature of the power semiconductor switches and / or electric converter unit (14) and change operating state from the first operating state to the second operating state if, in addition to reaching the predetermined motor speed and predetermined estimated required current value, a certain measured and / or simulated temperature threshold limit is reached.

16. The electrical converter cell (14) according to claim 13, characterized in that The electric converter unit (14) is configured to measure and / or simulate an internal temperature of the power semiconductor switches and / or electric converter unit (14) and change operating state from the first operating state to the second operating state only when a certain measured and / or simulated temperature threshold limit is reached, regardless of the motor speed and estimated required current value.

17. The electrical converter cell (14) according to any of claims 13 to 16, characterized in that The electric converter unit (14) comprises a first gate resistance value, a second gate resistance value, and means for switching between the first gate resistance value and the second gate resistance value, wherein the first gate resistance value is higher than the second gate resistance value.

18. The electrical converter cell (14) according to any of claims 13 to 16, characterized in that The electric converter unit (14) is arranged to increase the switching speed of the power semiconductor switches by using a lower gate resistance value of the power semiconductor switches.

19. The electrical converter cell (14) according to claim 17, characterized in that The electrical converter unit (14) is configured to use the second gate resistance value in the second operating state and the first gate resistance value in the first operating state.

20. The electrical converter cell (14) according to any of claims 13 to 16, characterized in that The electrical converter unit (14) comprises a first gate control voltage, a second gate control voltage and means for switching between the first gate control voltage and the second gate control voltage, wherein the first gate control voltage is lower than the second gate control voltage.

21. The electrical converter cell (14) according to any of claims 13 to 16, characterized in that The electrical converter unit (14) is configured to increase the switching speed of the power semiconductor switch by increasing the gate control voltage of the power semiconductor switch.

22. The electrical converter cell (14) according to claim 20, characterized in that The electrical converter unit (14) is configured to use the first gate control voltage in the first operating state and the second gate control voltage in the second operating state.

23. The electrical converter cell (14) according to any of claims 13 to 16, characterized in that The electrical motor (12) is an elevator motor (12) of an elevator (100).

24. The electrical converter cell (14) according to any of claims 13 to 16, characterized in that The electrical motor (12) is one of the following: synchronous reluctance motor, permanent magnet motor, permanent magnet linear motor, permanent magnet assisted synchronous reluctance motor, linear switched reluctance motor.

25. The electrical converter cell (14) according to any of claims 13 to 16, characterized by The electrical converter unit comprises a converter device (14D).

26. An elevator (100) comprising an elevator car (10), an elevator motor (12) configured to move the elevator car (10), an electrical converter unit (14) for operating the elevator motor (12), and a control unit (1000; 14A) configured to control the elevator and / or the electrical converter unit (14), characterized in that the electrical converter unit (14) is the electrical converter unit (14) according to any one of the preceding claims 13 to 25.

Images