WO2002021674A1 - Power supply for high speed motor - Google Patents

Power supply for high speed motor Download PDF

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Publication number
WO2002021674A1
WO2002021674A1 PCT/AU2001/001126 AU0101126W WO0221674A1 WO 2002021674 A1 WO2002021674 A1 WO 2002021674A1 AU 0101126 W AU0101126 W AU 0101126W WO 0221674 A1 WO0221674 A1 WO 0221674A1
Authority
WO
WIPO (PCT)
Prior art keywords
motor
buss
power
power supply
controller
Prior art date
Application number
PCT/AU2001/001126
Other languages
French (fr)
Inventor
Huai Yu Lin
Ronald David Conry
Original Assignee
Turbocor Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Turbocor Inc filed Critical Turbocor Inc
Priority to AU2001285599A priority Critical patent/AU2001285599A1/en
Publication of WO2002021674A1 publication Critical patent/WO2002021674A1/en

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C32/00—Bearings not otherwise provided for
    • F16C32/04—Bearings not otherwise provided for using magnetic or electric supporting means
    • F16C32/0406—Magnetic bearings
    • F16C32/044—Active magnetic bearings
    • F16C32/0444—Details of devices to control the actuation of the electromagnets
    • F16C32/0457—Details of the power supply to the electromagnets
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C32/00—Bearings not otherwise provided for
    • F16C32/04—Bearings not otherwise provided for using magnetic or electric supporting means
    • F16C32/0406—Magnetic bearings
    • F16C32/044—Active magnetic bearings
    • F16C32/0442—Active magnetic bearings with devices affected by abnormal, undesired or non-standard conditions such as shock-load, power outage, start-up or touchdown
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J9/00—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting
    • H02J9/04—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source
    • H02J9/06—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source with automatic change-over, e.g. UPS systems
    • H02J9/066—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source with automatic change-over, e.g. UPS systems characterised by the use of dynamo-electric machines
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2380/00—Electrical apparatus
    • F16C2380/26—Dynamo-electric machines or combinations therewith, e.g. electro-motors and generators

Definitions

  • This invention relates to a power supply for a high speed electric motor and relates particularly to a power supply for a motor using magnetic bearings.
  • a known difficulty with use of magnetic bearings is to supply power to the bearings during a system power failure where the power supply to the motor fails. While it is known to supply auxiliary or back-up power supplies to the system by way of batteries of the like, such auxiliary power supplies are relatively expensive and require additional switching controls to enable the auxiliary supply to take over when the main power supply fails. Further, the batteries have a limited life and generally must be replaced every two (2) years. This adds substantial further costs to the system.
  • a power control system for a high speed electric motor with at least one magnetic bearing comprising a DC/DC converter supplied from a DC link buss connected to a main power supply, said buss supplying power for the electric motor and a bearing actuator, the converter providing low voltage DC power supplies for a motor controller, a bearing controller and a supervisory controller, the supervisory controller monitoring the main power supply and communicating with the motor controller and bearing controller so as to cause the motor to operate as a generator in the event of a failure of the main power supply to thereby supply power to the DC link buss to maintain operation of the magnetic bearing.
  • the invention is particularly adapted for use with a high electric motor the rotor of which is supported solely by magnetic bearings.
  • the invention may also be utilised for an electric motor having a combination of magnetic and gas bearings.
  • the DC link buss incorporates at least one capacitor which, in normal use, is maintained in a charged condition by the main power supply.
  • the capacitor is able to provide sufficient power in conjunction with that supplied by the motor running as a generator to run down the motor from full speed and maintain operation of the magnetic bearings during the run down period.
  • Running the motor as a generator during the run down period extracts the kinetic energy stored in the motor and other rotating parts and constitutes an electric brake to quickly and safely stop the rotor rotation.
  • power continues to be supplied from the motor, running as a generator, to the DC link buss which provides an uninterruptable power supply to the DC/DC converter and the several controllers as well as the magnetic bearing actuator for the full run down period.
  • a method of running down a high speed, DC electric motor run on magnetic bearings in the event of a failure of the main power supply including the steps of supplying the motor and the magnetic bearings from a high voltage DC buss connected to the main power supply, providing a DC/DC controller to supply low voltage DC power to a magnetic bearing controller and a motor controller, using switching devices to control the motor operation, sensing a main power supply failure and providing a signal to the motor controller, controlling the switching devices to cause the rotating motor to run as a generator, and supplying the generated power to the DC buss to maintain operation of the magnetic bearings.
  • FIG. 1 is a block diagram of a power control system in accordance with the present invention.
  • the power control system 12 is connected to a three phase AC power supply 14 through a bridge rectifier 16.
  • a DC link buss 17 supplies DC power to a DC/DC converter 18, magnetic bearing actuator 19 and electric motor 21.
  • a large capacitor 22 is connected across the link buss 17 to provide a buffer of stored power for motor run down.
  • the DC link buss voltage is 1000V and the capacitor, or several capacitors, will have a capacity sufficient for a motor run down time of about 0.1 sec to about 1.5 sec, in the absence of any other power source.
  • the DC DC converter 18 provides low voltage DC power for a motor controller 23, a bearing controller 24 and a supervisory controller, which, in this embodiment, takes the form of a computer 26.
  • the converter 18 also supplies low voltage power for various sensors associated with the magnetic bearings and for Insulated Gate Bipolar Transistors (IGBT) which are used for control purposes in the magnetic bearing actuator 19 and the electric motor power supply 21.
  • IGBT Insulated Gate Bipolar Transistors
  • the magnetic bearing actuators and associated IGBTs and the electric motor control circuits and its associated IGBTs are known in the art and will not be described in detail.
  • Gate drive signals for the various IGBTs are generated by the bearing controller 24 and motor controller 23, respectively, to provide the desired operational parameters for the electric motor and the electric motor bearings.
  • An AC power monitor 27 provides a signal to the supervisory computer 26 in the event of a failure of the main AC power supply 14. On receipt of such a signal, the motor controller 23 controls the motor current to reverse relative to the motor magnetic field thereby turning the electric motor into a generator.
  • the motor controller controls the operation of a number of electronic switches (6 in a 3-phase motor) between "open” and “closed” conditions to direct the motor current through the motor windings for controlling the motor parameters.
  • the switches are actuated to short the motor windings for a period to generate winding current when the voltage on the capacitor 22 is higher than the motor voltage.
  • the switches are then actuated to connect the motor winding, in generator mode, to the DC buss 17 to feed power to the DC buss 17.
  • the power developed by the motor/generator 21 is fed into the DC link buss 17 via the motor IGBTs to maintain the power supply for the magnetic bearings 18.
  • the rotor By drawing power from the motor 21, the rotor is electrically braked thereby taking potentially hazardous kinetic energy away from the rotor shaft.
  • the power generated during the run down together with the power stored in the capacitor 22 maintains the power supply to the magnetic bearings 18 and the controllers 23 and 24 for sufficient time to enable the motor 21 and associated rotating parts to run down to a stop.
  • the supervisory computer when the electric motor is used to drive a refrigeration compressor, the supervisory computer, on sensing a power failure, will also operate to unload the compressor.
  • a run down time of between 2 to 3 seconds is achievable.
  • the motor 21 as a generator and supplying power to the DC link buss 17, the charge in the capacitor 22 is maintained for a substantial part of the run down time.

Abstract

A power supply system for a high speed DC electric motor includes a high voltage DC buss (17) which supplies DC power to the motor (21) and magnetic bearing actuator(19). A capacitor (22) is connected into the DC buss and in maintained in a charged condition by the buss voltage. A DC/DC converter (18) connected to the DC buss supplies low voltage DC power to the motor controller (23) and the bearing controller (24). In the event of a power failure, a signal is generated which causes the motor controller to reverse the motor magnetic field to thereby turn the motor into a generator and supply power to the DC buss.

Description

POWER SUPPLY FOR HIGH SPEED MOTOR
Field of the Invention
This invention relates to a power supply for a high speed electric motor and relates particularly to a power supply for a motor using magnetic bearings.
International Patent Application No WO 98/33260 describes a high speed electric motor which is particularly suitable for use as a refrigeration compressor motor. Such a motor may be used in, for example, a compressor of the type described in Australian Patent No 686174 and utilizing magnetic bearings for the rotating parts.
Background of the Invention
A known difficulty with use of magnetic bearings is to supply power to the bearings during a system power failure where the power supply to the motor fails. While it is known to supply auxiliary or back-up power supplies to the system by way of batteries of the like, such auxiliary power supplies are relatively expensive and require additional switching controls to enable the auxiliary supply to take over when the main power supply fails. Further, the batteries have a limited life and generally must be replaced every two (2) years. This adds substantial further costs to the system.
It is therefore desirable to provide an improved power supply system for a high speed electric motor running in magnetic bearings which can maintain power to the bearings in the event of a main power supply failure.
It is also desirable to provide a power supply system for continuously supplying power to the magnetic bearings of a high speed electric motor following a failure of the main power supply until such time as the rotating parts are at rest.
It is also desirable to provide an improved controller for a high speed electric motor which enables a spinning rotor to spin down under controlled conditions.
It is also desirable to provide a power supply controller for a high speed electric motor with magnetic bearings which is relatively inexpensive, which is efficient in its operation and which provides a substantially fail-safe power supply for the magnetic bearings.
Summary of the Invention
In accordance with one aspect of the invention there is provided a power control system for a high speed electric motor with at least one magnetic bearing comprising a DC/DC converter supplied from a DC link buss connected to a main power supply, said buss supplying power for the electric motor and a bearing actuator, the converter providing low voltage DC power supplies for a motor controller, a bearing controller and a supervisory controller, the supervisory controller monitoring the main power supply and communicating with the motor controller and bearing controller so as to cause the motor to operate as a generator in the event of a failure of the main power supply to thereby supply power to the DC link buss to maintain operation of the magnetic bearing.
The invention is particularly adapted for use with a high electric motor the rotor of which is supported solely by magnetic bearings. The invention may also be utilised for an electric motor having a combination of magnetic and gas bearings.
Preferably, the DC link buss incorporates at least one capacitor which, in normal use, is maintained in a charged condition by the main power supply. The capacitor is able to provide sufficient power in conjunction with that supplied by the motor running as a generator to run down the motor from full speed and maintain operation of the magnetic bearings during the run down period. Running the motor as a generator during the run down period extracts the kinetic energy stored in the motor and other rotating parts and constitutes an electric brake to quickly and safely stop the rotor rotation. During the run down period, power continues to be supplied from the motor, running as a generator, to the DC link buss which provides an uninterruptable power supply to the DC/DC converter and the several controllers as well as the magnetic bearing actuator for the full run down period.
In accordance with another aspect of the invention there is provided a method of running down a high speed, DC electric motor run on magnetic bearings in the event of a failure of the main power supply including the steps of supplying the motor and the magnetic bearings from a high voltage DC buss connected to the main power supply, providing a DC/DC controller to supply low voltage DC power to a magnetic bearing controller and a motor controller, using switching devices to control the motor operation, sensing a main power supply failure and providing a signal to the motor controller, controlling the switching devices to cause the rotating motor to run as a generator, and supplying the generated power to the DC buss to maintain operation of the magnetic bearings.
One embodiment of the invention will now be described with reference to the accompanying drawing in which Figure 1 is a block diagram of a power control system in accordance with the present invention.
Description of one embodiment
Referring to the drawing, the power control system 12 is connected to a three phase AC power supply 14 through a bridge rectifier 16. A DC link buss 17 supplies DC power to a DC/DC converter 18, magnetic bearing actuator 19 and electric motor 21. A large capacitor 22 is connected across the link buss 17 to provide a buffer of stored power for motor run down. In this embodiment, the DC link buss voltage is 1000V and the capacitor, or several capacitors, will have a capacity sufficient for a motor run down time of about 0.1 sec to about 1.5 sec, in the absence of any other power source.
The DC DC converter 18 provides low voltage DC power for a motor controller 23, a bearing controller 24 and a supervisory controller, which, in this embodiment, takes the form of a computer 26. The converter 18 also supplies low voltage power for various sensors associated with the magnetic bearings and for Insulated Gate Bipolar Transistors (IGBT) which are used for control purposes in the magnetic bearing actuator 19 and the electric motor power supply 21. The magnetic bearing actuators and associated IGBTs and the electric motor control circuits and its associated IGBTs are known in the art and will not be described in detail. Gate drive signals for the various IGBTs are generated by the bearing controller 24 and motor controller 23, respectively, to provide the desired operational parameters for the electric motor and the electric motor bearings.
An AC power monitor 27 provides a signal to the supervisory computer 26 in the event of a failure of the main AC power supply 14. On receipt of such a signal, the motor controller 23 controls the motor current to reverse relative to the motor magnetic field thereby turning the electric motor into a generator.
To do this, the motor controller controls the operation of a number of electronic switches (6 in a 3-phase motor) between "open" and "closed" conditions to direct the motor current through the motor windings for controlling the motor parameters. When a power failure is detected, the switches are actuated to short the motor windings for a period to generate winding current when the voltage on the capacitor 22 is higher than the motor voltage. The switches are then actuated to connect the motor winding, in generator mode, to the DC buss 17 to feed power to the DC buss 17. The power developed by the motor/generator 21 is fed into the DC link buss 17 via the motor IGBTs to maintain the power supply for the magnetic bearings 18. By drawing power from the motor 21, the rotor is electrically braked thereby taking potentially hazardous kinetic energy away from the rotor shaft. The power generated during the run down together with the power stored in the capacitor 22 maintains the power supply to the magnetic bearings 18 and the controllers 23 and 24 for sufficient time to enable the motor 21 and associated rotating parts to run down to a stop.
In one particular form of the invention, when the electric motor is used to drive a refrigeration compressor, the supervisory computer, on sensing a power failure, will also operate to unload the compressor.
Subject to the motor speed, the inertia of the rotating parts associated with the motor and any external load on the motor, a run down time of between 2 to 3 seconds is achievable. By operating the motor 21 as a generator and supplying power to the DC link buss 17, the charge in the capacitor 22 is maintained for a substantial part of the run down time. By maintaining a power supply to the magnetic bearings during run down, damage to the bearings is avoided and the motor is able to be safely brought to rest.

Claims

CLAIMS:
1. A power control system for a high speed electric motor with at least one magnetic bearing comprising a DC/DC converter supplied from a DC link buss connected to a main power supply, said buss supplying power for the electric motor and a bearing actuator, the converter providing low voltage DC power supplies for a motor controller, a bearing controller and a supervisory controller, the supervisory controller monitoring the main power supply and communicating with the motor controller and bearing controller so as to cause the motor to operate as a generator in the event of a failure of the main power supply to thereby supply power to the DC link buss to maintain operation of the magnetic bearing.
2. A power control system according to claim 1 wherein the rotor of the electric motor is supported solely by magnetic bearings.
3. A power control system according to claim 1 or claim 2 wherein at least one capacitor is connected across the DC buss and is maintained in a state of charge by the buss voltage while a power supply is maintained to the DC buss.
4. A power control system according to claim 3 wherein the motor, run as a generator, supplies sufficient power to the DC buss during run down of the motor and any connected rotating parts to maintain, together with the capacitor, sufficient power for actuation of the magnetic bearings until the motor has come to a stop.
5. A power control system according to any one of the preceding claims wherein the motor controller, on receipt of a signal indicating a failure of the main power supply, controls the motor current to cause the motor magnetic field to reverse thereby turning the motor into a generator.
6. A power control system according to claim 5 including switching devices controlled by the motor controller which, when a power failure occurs, short circuits the motor windings for a period of time to establish a generated current to supply the DC buss, the switching devices being switched to cause the generated current to flow to the DC buss when the generated voltage is greater than the DC buss voltage.
7. A power control system according to any one of the preceding claims wherein the DC buss voltage is between 500v and 1200v, and the run down time is between 2 and 5 seconds..
8. A method of running down a high speed, DC electric motor run on magnetic bearings in the event of a failure of the main power supply including the steps of supplying the motor and the magnetic bearings from a high voltage DC buss connected to the main power supply, providing a DC/DC controller to supply low voltage DC power to a magnetic bearing controller and a motor controller, using switching devices to control the motor operation, sensing a main power supply failure and providing a signal to the motor controller, controlling the switching devices to cause the rotating motor to run as a generator, and supplying the generated power to the DC buss to maintain operation of the magnetic bearings.
9. A method according to claim 8 including the steps of connecting at least one capacitor into the DC buss, maintaining the capacitor in a charged state by the buss voltage while a power supply is maintained to the DC buss, and using the capacitor charge in conjunction with the power supplied by the motor run as a generator to maintain sufficient power in the DC buss to maintain operation of the magnetic bearings for a motor run down period if the main power supply fails.
10. A method according to claim 8 including the steps of controlling the motor control switching devices to short the motor windings on receipt of a power failure signal, monitoring the DC buss voltage, and connecting the windings to the DC buss when the motor is running as a generator and generating power at a voltage higher than the DC buss voltage.
11. A method according to claim 8, 9 or 10 including the steps of running the motor as a generator to constitute an electric brake to quickly and safely stop the rotor rotation, while, during the run down period, power continues to be supplied from the motor, running as a generator, to the DC link buss which provides an unmterruptable power supply to the DC/DC converter and the motor and magnetic bearing controllers.
12. A power control system for controlling the run down of a high speed electric motor with at least one magnetic substantially as hereinbefore described with reference to the accompanying drawings.
13. A method of running down a high speed, DC electric motor run on magnetic bearings in the event of a failure of the main power supply including the steps hereinbefore described with reference to the accompanying drawings.
PCT/AU2001/001126 2000-09-11 2001-09-07 Power supply for high speed motor WO2002021674A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2001285599A AU2001285599A1 (en) 2000-09-11 2001-09-07 Power supply for high speed motor

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AUPR0024 2000-09-11
AUPR0024A AUPR002400A0 (en) 2000-09-11 2000-09-11 Power supply for high speed motor

Publications (1)

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WO2002021674A1 true WO2002021674A1 (en) 2002-03-14

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102198900A (en) * 2010-03-23 2011-09-28 上海三菱电梯有限公司 Backup source operation control system of energy feedback elevator
EP3346151A1 (en) * 2017-01-06 2018-07-11 LG Electronics Inc. Compressor driving apparatus and chiller including the same
EP3640488A4 (en) * 2017-11-07 2020-09-02 Gree Green Refrigeration Technology Center Co. Ltd. of Zhuhai Power supply system for magnetic bearing and control method therefor
EP3872976A4 (en) * 2018-12-17 2021-12-22 Gree Electric Appliances, Inc. of Zhuhai Power consumption control device, magnetic levitation system, and power consumption control method
US11973400B2 (en) 2018-12-17 2024-04-30 Gree Electric Appliances, Inc. Of Zhuhai Power consumption control device, magnetic levitation system, and power consumption control method

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5574345A (en) * 1994-02-28 1996-11-12 Ntn Corporation Power supply circuit for magnetic bearing system
US5726560A (en) * 1995-09-01 1998-03-10 Barber-Colman Company Switched reluctance generator
US5757148A (en) * 1996-03-13 1998-05-26 Ebara Corporation Method of and apparatus for stopping a motor having magnetic bearings
US5917297A (en) * 1996-07-25 1999-06-29 Lust Antriebstechnik Gmbh Arrangement and method for operating a magnetically suspended, electromotoric drive apparatus in the event of a mains disturbance

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5574345A (en) * 1994-02-28 1996-11-12 Ntn Corporation Power supply circuit for magnetic bearing system
US5726560A (en) * 1995-09-01 1998-03-10 Barber-Colman Company Switched reluctance generator
US5757148A (en) * 1996-03-13 1998-05-26 Ebara Corporation Method of and apparatus for stopping a motor having magnetic bearings
US5917297A (en) * 1996-07-25 1999-06-29 Lust Antriebstechnik Gmbh Arrangement and method for operating a magnetically suspended, electromotoric drive apparatus in the event of a mains disturbance

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102198900A (en) * 2010-03-23 2011-09-28 上海三菱电梯有限公司 Backup source operation control system of energy feedback elevator
EP3346151A1 (en) * 2017-01-06 2018-07-11 LG Electronics Inc. Compressor driving apparatus and chiller including the same
US10677496B2 (en) 2017-01-06 2020-06-09 Lg Electronics Inc. Compressor driving apparatus and chiller including the same
EP3640488A4 (en) * 2017-11-07 2020-09-02 Gree Green Refrigeration Technology Center Co. Ltd. of Zhuhai Power supply system for magnetic bearing and control method therefor
US11454278B2 (en) 2017-11-07 2022-09-27 Gree Green Refrigeration Technology Center Co., Ltd. Of Zhuhai Power supply system for magnetic bearing and control method therefor
EP3872976A4 (en) * 2018-12-17 2021-12-22 Gree Electric Appliances, Inc. of Zhuhai Power consumption control device, magnetic levitation system, and power consumption control method
US11973400B2 (en) 2018-12-17 2024-04-30 Gree Electric Appliances, Inc. Of Zhuhai Power consumption control device, magnetic levitation system, and power consumption control method

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