Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K21/00—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets
  • H02K21/02—Details
  • H02K21/04—Windings on magnets for additional excitation ; Windings and magnets for additional excitation
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02K—DYNAMO-ELECTRIC MACHINES
  • H02K21/00—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets
  • H02K21/02—Details
  • H02K21/04—Windings on magnets for additional excitation ; Windings and magnets for additional excitation
  • H02K21/042—Windings on magnets for additional excitation ; Windings and magnets for additional excitation with permanent magnets and field winding both rotating
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
  • H02P29/00—Arrangements for regulating or controlling electric motors, appropriate for both AC and DC motors
  • H02P29/02—Providing protection against overload without automatic interruption of supply
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
  • H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
  • H02P6/34—Modelling or simulation for control purposes

Definitions

• the invention is based on a brushless DC drive according to the preamble of patent claim 1.
• Permanent magnet-excited, brushless DC drives are used in motor vehicles for a variety of purposes, including for electric power steering. These DC drives have a synchronous motor with a stator or armature winding and a permanent magnet excited rotor. The armature winding is connected to the via an inverter in a bridge circuit with semiconductor circuit breakers
• the inverter which commutates the stator winding is controlled by an electronic control unit.
• DE 37 09 168 AI describes a synchronous motor operated on a DC voltage network, in which three of one Control device-controlled semiconductor circuit breakers are arranged in the winding phases of the star winding connected in a star. If faults occur in the stator winding and / or in the • circuit breakers, the DC drive can generate a permanent electromagnetic braking torque without a DC voltage being applied, since the synchronous motor now works as a generator against a low load resistance. In many applications, such a braking torque affects the function of the unit or system in which the DC drive is used. In electric power steering, for example, the braking torque that occurs in the event of a fault forces considerable steering forces that the driver can control with his own
• DC drive does not have a disruptive or disadvantageous influence on the unit or the system, ie it works as if the DC drive was not present.
• a mechanical clutch is used to generate the desired fail-silent behavior, via which the output shaft of the synchronous motor engages in the steering gear. In the event of a fault, the clutch is opened and the motor is mechanically separated from the steering system.
• a hybrid-excited electrical machine is known (EP 0 729 217 B1) in which the magnetic field of the rotor is generated both by means of permanent magnets and by means of a field excitation winding supplied with excitation current via slip rings.
• the rotor is axially divided into two rotor halves, which are mounted on the rotor shaft at an axial distance from one another. In the laminated core of each rotor half, receiving openings are provided, into which the permanent or permanent magnets are inserted.
• the permanent magnets are arranged in polarity 'in the rotor halves so as to in a rotor with its half. Point the north pole and in the other half of the rotor with their south pole to the air gap of the machine.
• the permanent magnets in the two rotor halves are offset from one another by one pole pitch.
• the field excitation winding designed as a ring coil is inserted into the space between the two rotor halves. If the field excitation winding is supplied with direct current, then a magnetic flux which increases or weakens the magnetic flux of the permanent magnets, depending on the current direction of the excitation current, is generated. This results in a large control range for the speed or voltage of the machine.
• the brushless DC drive according to the invention with the features of claim 1 has the advantage that the desired fail-silent behavior of the DC drive without expensive external components, such as mechanical clutches, with simple control processes in
• the magnetic field of the permanent magnets can be reduced or canceled by the magnetic field of the field excitation winding, so that no or only a reduced induced voltage occurs in the synchronous motor and therefore no or only a reduced short-circuit current can flow, which has no or only a very small one Braking torque generated.
• a moderate, temperature-dependent reduction in the magnetic field leads to a reduction in the braking torque and prevents irreversible demagnetization of the permanent magnets and thus their permanent damage. If a reduction in Bre smor ⁇ ents is not sufficient, the magnetic field can be made zero overall, but then the permanent damage to the permanent magnets must be accepted.
• the field excitation winding has a number of coils corresponding to the number of permanent magnets, each of which encloses one of the permanent magnets.
• the coils are connected in parallel or in series and are rotatably connected to the rotor connected slip ring pair connected.
• 1 is a circuit diagram of a brushless DC drive
• FIG. 2 schematically shows a cross section of a three-phase, four-pole synchronous motor in the DC drive according to FIG. 1,
• FIG. 3 shows a schematic view of the rotor of the synchronous motor in FIG. 2.
• brushless DC drive has a synchronous motor 10, which is operated by means of a switching device 11 for electronic commutation on a DC voltage network, which is marked in FIG. 1 with "+" and "-" and with
• the synchronous motor 10 has, in a known manner, a stator 12 and a rotor 13 which is seated on a rotor shaft 14 (FIG. 2) which is rotatably mounted in a housing.
• the stator 12 carries an armature or stator winding 15 which, in the exemplary embodiment, is of three-phase design and whose winding phases 151-153 are connected in star.
• the winding connections 1, 2 and 3 of the stator winding 15 are each connected to the switching device 11 via a connecting line 16.
• the switching device 11 designed as a B6 inverter has six semiconductor power switches 15 in a bridge circuit, which in the exemplary embodiment are designed as MOS-FETs.
• the connecting lines 16 leading to the winding connections 1, 2 and 3 are each connected to one of the taps 4, 5 and 6 of the bridge branches each formed by series connection of two circuit breakers 17, which are connected by two circuit breakers 17 each.
• the circuit breakers 17 can be controlled by an electronic control unit 18.
• the rotor 13 which is only symbolically indicated in FIG. 1 and is shown schematically in section in FIGS. 2 and 3, has a rotor body 19 formed by a laminated plate assembly or a solid iron assembly, which is seated in a rotationally fixed manner on the rotor shaft 14, and several which are fixed on the outside of the rotor body 19
• Permanent magnetic poles 20 The rotor 13 outlined in FIG. 2 is designed with four poles and accordingly has four permanent magnet poles 20, each offset by 90 ° on the circumference of the rotor body 19, successive permanent magnet poles 20 having alternating polarity “N” and “S”, as shown in FIG. 3.
• a field excitation winding 21 is also accommodated on the rotor body 19 and is connected to a pair of slip rings 22, 23 that are seated in a rotationally fixed manner on the rotor shaft 14.
• the field excitation winding 21 consists of a total of four coils 24, one coil 24 in each case being wound around one of the permanent magnet poles 20, that is to say enclosing the permanent magnet pole 20 on its four side surfaces which extend in the axial direction and in the circumferential direction.
• the coils 24 are connected in parallel in the exemplary embodiment of FIGS. 2 and 3, and the parallel connection is connected to the slip rings 22, 23. Alternatively, the coils 24 can also be connected in series. The coils 24 are wound in such a way that the excitation current drawn from the slip rings 22, 23 ′′ generates an inverse magnetic field in successive coils 24.
• the field excitation winding 21 is part of a device for forcing a so-called fail-silent behavior of the direct current drive, which ensures that if a fault occurs in the direct current drive, which can be caused, for example, by a defective circuit breaker 17 or a winding short in the stator winding 15, the system interacting with the DC drive is not adversely affected or disturbed.
• this device also has one in the control unit 18 integrated control device 25, three in each 'one winding phase 151, 152, 153 arranged in the measuring shunt 26, and an engine temperature detecting temperature sensor 27.
• the measuring shunts 26 and the temperature sensor 27 are connected to inputs of the control device 25 via measuring lines 28.
• control device 25 Two outputs of the control device 25 are connected to the slip rings 22, 23 via control lines 29.
• the control device 25 measures the currents flowing through the measuring shunts 26 according to magnitude and phase and adds them vectorially. If the DC drive is error-free, the result of the addition is always zero. If the vector sum deviates significantly from zero, there is an error in the winding phases 151-153 or in the circuit breakers 17. In this case, the control device 25 controls the circuit breaker 32 in such a way that it opens, and an excitation current is applied to the field excitation winding 21, which generates a magnetic flux opposite the magnetic flux of the permanent magnet poles 20 ' via the coils 24 ' .
• the field of excitation of the synchronous motor 10 is weakened, so that no or only a small voltage is induced in the stator winding 15 and therefore no or only a small braking torque occurs.
• the weakening of the magnetic field is carried out as a function of the temperature of the synchronous motor 10, which is detected by the temperature sensor 27 and fed to the control device 25. The. Temperature dependent The magnetic field is weakened in such a way that irreversible demagnetization of the permanent magnet poles 20 is avoided and thus permanent damage to the synchronous motor 10 is excluded.
• the size of the excitation current applied by the control device 25 to the slip rings 22, 23 ' which can be set, for example, by means of pulse width modulation, is regulated as a function of the phase current in the stator winding 15, that is to say the excitation current is increased until the field weakening thereby achieved is only one low voltage induced and thus only a low short-circuit current flows, which generates an acceptable braking torque. If this reduction in the braking torque is not sufficient, the resulting excitation field can be brought to zero, in which case, however, the permanent damage to the permanent magnet poles 20 must be accepted.
• the device for enforcing fail-silent behavior can advantageously also be used in normal operation of the DC drive. If the current direction in the field excitation winding 21 is selected such that the magnetic field generated by it is added to the magnetic field of the permanent magnet poles 20, a motor with a high power density is produced. If the current direction in the field excitation winding .21 is reversed and the resulting magnetic field is weakened, higher speeds can be set. The size of the field gain or field weakening is in turn set by the control device 25 by means of pulse width modulation of the direct current supplied to the slip rings 22, 23. The current interrupter 32 is not activated.

Landscapes

• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Control Of Motors That Do Not Use Commutators (AREA)
• Permanent Magnet Type Synchronous Machine (AREA)
• Brushless Motors (AREA)
• Control Of Ac Motors In General (AREA)

Applications Claiming Priority (3)

Publications (1)

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ID=7685391

Family Applications (1)

Country Status (6)

Families Citing this family (29)

Family Cites Families (12)

• 2001
  • 2001-05-18 DE DE10124436A patent/DE10124436A1/de not_active Ceased
• 2002
  • 2002-03-16 JP JP2002592256A patent/JP2004519999A/ja active Pending
  • 2002-03-16 EP EP02732332A patent/EP1400003A1/de not_active Withdrawn
  • 2002-03-16 WO PCT/DE2002/000968 patent/WO2002095903A1/de active Application Filing
  • 2002-03-16 US US10/333,181 patent/US6828702B2/en not_active Expired - Fee Related
  • 2002-03-16 KR KR10-2003-7000604A patent/KR20030020372A/ko not_active Application Discontinuation

Non-Patent Citations (1)

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