METHOD FOR BRAKING A COMPRESSOR, COMPRESSOR OF A REFRIGERATION APPLIANCE, AN AIR CONDITIONING APPLIANCE OR A HEAT PUMP, AND REFRIGERATION APPLIANCE, AIR CONDITIONING APPLIANCE OR HEAT PUMP HAVING THE COMPRESSOR

Abstract

A method is provided for braking a compressor of a refrigeration appliance, of an air conditioning appliance or of a heat pump in which the compressor has a brushless motor with windings and a controller for braking the motor. The controller is configured to brake the brushless motor by using a braking current in a controlled manner starting from an operating rotational speed, in which the braking current during the controlled braking is dependent on induced voltages determined before the controlled braking. The method for braking includes rotating the motor at an operating rotational speed, receiving a signal for decelerating, braking or slowing down, determining voltages induced in the windings and supplying a braking current having a decreasing frequency to the windings, in which the braking current during the braking is dependent on the previously determined induced voltages. A compressor and a refrigeration appliance having the compressor are also provided.

Claims

1-15 (canceled)

16. A method for braking a compressor of a refrigeration appliance, of an air conditioning appliance or of a heat pump, the method comprising the following steps: a) rotating a brushless motor at an operating rotational speed for driving the compressor; b) receiving a signal for slowing down the brushless motor; c) determining voltages induced in windings of the brushless motor; and d) energizing the windings of the brushless motor with a braking current at a decreasing frequency, the braking current during braking being a function of the previously determined induced voltages.

17. The method according to claim 16, which further comprises providing the signal for slowing down as a preselected rotational speed being smaller than the operating rotational speed.

18. The method according to claim 17, which further comprises providing the signal for slowing down as a preselected rotational speed of zero.

19. The method according to claim 16, which further comprises determining a load torque for determining the braking current from the determined induced voltages.

20. The method according to claim 16, which further comprises upon receiving the signal for slowing down, approaching a limit rotational speed by using a rotational speed regulation, and deactivating the rotational speed regulation upon reaching the limit rotational speed.

21. The method according to claim 20, which further comprises approaching the limit rotational speed by using a conventional or ramp-type rotational speed regulation.

22. The method according to claim 20, which further comprises operating the brushless motor at an operating rotational speed above the limit rotational speed, and setting the limit rotational speed as a rotational speed above which the brushless motor is controlled by determining a rotor position using measured induced voltages.

23. The method according to claim 16, which further comprises carrying out the step of energizing the windings of the brushless motor with a braking current at a frequency decreasing in a ramp-type manner.

24. The method according to claim 16, which further comprises measuring induced voltages after slowing down to a rotational speed of zero.

25. The method according to claim 16, which further comprises stopping the energizing step after slowing down.

26. The method according to claim 16, which further comprises carrying out the energizing step with a substantially sinusoidal current.

27. The method according to claim 26, which further comprises generating the substantially sinusoidal current by pulse width modulation.

28. A compressor of a refrigeration appliance, of an air conditioning appliance or of a heat pump, the compressor comprising: a brushless motor having windings; and a controller for braking said brushless motor starting from an operating rotational speed, said controller being configured to slow down said brushless motor in a controlled manner with a braking current, and said braking current during controlled braking being a function of induced voltages determined before said controlled braking.

29. The compressor according to claim 28, wherein said controller is configured for: a) rotating said brushless motor at said operating rotational speed; b) providing a signal for slowing down said brushless motor; c) determining said voltages induced in said windings of said brushless motor; and d) energizing said windings of said brushless motor with said braking current at a decreasing frequency.

30. A refrigeration appliance, air conditioning appliance or heat pump, comprising a compressor according to claim 28.

Description

[0025] Further features and advantages of the invention will emerge from the description which follows of exemplary embodiments with reference to the accompanying figures, in which:

[0026] FIG. 1 shows an equivalent circuit diagram of an electric motor, which is configured as a brushless motor, such as a PMSM or a BLDC motor, of an inventive compressor,

[0027] FIG. 2 shows a flow diagram of an inventive method, and

[0028] FIG. 3 shows a diagram of a rotational speed curve for braking an inventive compressor.

[0029] FIG. 1 shows an equivalent circuit diagram of a brushless motor 100, which can be used for example as a compressor drive in a refrigerator. The brushless motor 100 has a voltage source 110, an inverter 120, three motor windings or windings 130U, 130V, 130W and a controller 160.

[0030] The voltage source 110 supplies an intermediate circuit voltage between an intermediate circuit supply potential and an intermediate circuit ground. The inverter 120 has six switches T1 to T6, which are arranged in the form of a B6 bridge and supply the windings 130U, 130V and 130W with current. More precisely two switches T1 and T2, T3 and T4 and T5 and T6 respectively are connected in series between the intermediate circuit supply potential and the intermediate circuit ground. The nodes between the switches T1 and T2, T3 and T4 and T5 and T6 are each connected to one side of the windings 130U, 130V and 130W. On their other side the windings 130U, 130V and 130W are connected to a star point 140. Shunt resistors 150 are also provided between the switches T2, T4 and T6 respectively and the intermediate circuit ground.

[0031] The switches T1 to T6 can each comprise for example a power transistor and a freewheeling diode connected parallel thereto. The switches T1 to T6 are activated by means of control signals X1 to X6 supplied by a controller 160. The controller 160 here corresponds to an apparatus for controlling an electric motor. The windings 130 are activated in such a manner that a rotating magnetic field is generated, in which a rotor comprising a permanent magnet rotates. The motor is therefore a permanent magnet synchronous motor with three windings 130U, 130V and 130W, which is supplied with a three-phase voltage by means of the B6 inverter 120, exciting currents lu, lv and lw being generated through the windings 130U, 130V and 130W.

[0032] The inventive compressor of a refrigeration appliance has a brushless motor 100 with windings 130U, 130V and 130W and a controller 160 for braking the motor starting from an operating rotational speed, the controller 160 being designed to slow down the brushless motor 100 in a controlled manner with a braking current, the braking current during braking being a function of induced voltages determined before controlled braking.

[0033] The further properties of the controller 160 will emerge from the description which follows of the inventive method.

[0034] FIG. 2 shows a flow diagram 200 of an inventive method for braking a compressor of a refrigeration appliance, the compressor having a brushless motor with windings, like the brushless motor 100 with windings 130U, 130V and 130W and the controller 160, as known from FIG. 1.

[0035] The method starts with method step a), rotating 201 the motor at an operating rotational speed as an initial situation, in which according to method step b) a signal 202 for slowing down is received. In method step c) voltages induced in the windings 203 are determined and in method step d) the windings 204 are energized with a braking current at a decreasing frequency, the braking current during braking being a function of the induced voltages determined before controlled braking.

[0036] FIG. 3 shows a diagram 300 of a rotational speed curve 301 for braking an inventive compressor, on which the individual method steps can be completed and in which a number of embodiments are described. The rotational speed S is plotted over time t in diagram 300.

[0037] According to the embodiment of the invention illustrated in diagram 300 the method starts with method step a), rotating 201 the motor at a constantly shown operating rotational speed 302 as an initial situation. At time point t1 the controller receives 202 a signal 303 for slowing down according to method step b). In the illustrated exemplary embodiment the signal for slowing down is given in the form of a preselected rotational speed of zero. Until time point t1 a rotational speed regulator regulates the motor. When the signal 303 is received, the inventive controller takes over control of the motor.

[0038] Diagram 300 shows an embodiment according to which the rotational speed is still within the range of the rotational speed regulator at the time point of the signal 303 for slowing down. The inventive controller utilizes this, on receipt of the signal 303 for slowing down, first to approach a limit rotational speed 305 with a ramp-type rotational speed profile 304 using conventional rotational speed regulation. The limit rotational speed 305 is the lower limit of the regulating range of the rotational speed regulator. The limit rotational speed 305 is reached at time point t2, whereupon conventional the rotational speed regulator is deactivated.

[0039] In method step c) voltages induced in the windings are determined, 203, allowing the controller indirectly to detect the current load at the instantaneous rotational speed, in this instance the limit rotational speed 305.

[0040] This information is taken into account to allow controlled braking, with the windings being energized in method step d) with a braking current at a decreasing frequency 204. During such controlled braking the braking current during braking is a function of the induced voltages determined before controlled braking. The motor here is slowed down on a predefined rotational speed curve, in this instance with a ramp-type rotational speed profile 306, until it comes to a stop at time point t3.

[0041] It can be checked that the motor has stopped in that no more induced voltages can be determined. Energization is stopped after slowing.

[0042] Braking takes place in that the rotational speed is controlled on a predefined rotational speed curve, there being no need to monitor the rotor position constantly.

[0043] It should be noted that the segment shown in this embodiment with the regulated approach to the lower limit frequency, illustrated by the rotational speed profile 304, can be omitted. The voltages induced in the windings could also be determined and used for controlled braking immediately on receipt of the signal for slowing down at t1.

[0044] It would also be possible to determine the voltages induced in the windings immediately on receipt of the signal for slowing down at t1 and only to use said voltages after t2 for the controlled braking of the motor on a predefined rotational speed curve, as the externally predefined load conditions change at most insignificantly between t1 and t2.

[0045] In a compressor of a refrigeration appliance with a brushless motor 100 with windings 130U, 130V, 130W and a controller 160 for braking the motor starting from an operating rotational speed, the controller 160 is designed to slow down the motor in a controlled manner with a braking current, the braking current during controlled braking being a function of induced voltages determined before controlled braking, in other words before the start of the rotational speed profile 306 in diagram 300.

[0046] According to a further embodiment of the present invention the windings of the motor are energized with an essentially sinusoidal current, which is generated by means of pulse width modulation. Inductive inertia causes pulse width modulated voltages to be formed in controlled currents, resulting essentially in a sinusoidal current

LIST OF REFERENCE CHARACTERS

[0047] 100 Motor [0048] 110 Voltage source [0049] 120 Inverter [0050] 130U, 130V, 130W Windings [0051] 140 Star point [0052] 150 Resistor [0053] 160 Controller [0054] 200 Flow diagram [0055] 201 Rotating the motor at an operating rotational speed [0056] 202 Receiving a signal for slowing down [0057] 203 Determining voltages induced in the windings [0058] 204 Energizing windings with a braking current [0059] 300 Diagram [0060] 301 Rotational speed curve [0061] 302 Operating rotational speed [0062] 303 Signal for slowing down [0063] 304 Rotational speed profile [0064] 305 Limit rotational speed [0065] 306 Rotational speed profile [0066] T1 . . . T6 Switches [0067] t1, t1 Time points