Method and device for determining phase currents and an excitation current of an electrical machine, and motor system

Patent metadata

Field	Value
Publication number	US-2016197569-A1
Application number	US-201414912102-A
Country	US
Kind code	A1
Filing date	Aug 5, 2014
Priority date	Aug 15, 2013
Publication date	Jul 7, 2016
Grant date	—

Abstract

The invention relates to a method for determining the phase currents through phase windings ( 12 ) and an excitation current through an excitation winding ( 13 ) of an electrical machine ( 11 ), wherein an excitation winding ( 13 ) is connected between a star point ( 14 ) of the phase windings ( 12 ) and a defined reference potential, the method comprising the following steps: —periodic driving of the electrical machine ( 11 ) with a predefined pulse pattern ( 30 ); —determining a respective measurement current (I mess ) in a plurality of temporal measuring windows ( 31, 32, 33 ) of a measuring period ( 37 ), wherein the measurement currents (I mess ) correspond to currents through one of the phase windings ( 12 ) and through one or more parallel connections of a plurality of the phase windings ( 12 ); and —determining the phase currents and the excitation current by evaluating the measurement currents (I mess ) determined during the measuring period ( 37 ).

First claim

1 . A method for determining phase currents through phase windings ( 12 ) and a field current through a field winding ( 13 ) of an electrical machine ( 11 ), wherein a field winding ( 13 ) is connected between a star point ( 14 ) of the phase windings ( 12 ) and a specific reference potential ( 17 ),
the method comprising:
periodically driving the electrical machine ( 11 ) with a predefined pulse pattern ( 30 );
determining in each case one measurement current (I measure ) in a plurality of time measurement windows ( 31 , 32 , 33 ) of a measurement period ( 37 ), wherein the measurement currents (I measure ) comprise a current through one of the phase windings ( 12 ) and at least one current through one or more parallel circuits of a plurality of the phase windings ( 12 ); and
determining the phase currents and the field current by evaluating the measurement currents (I measure ) which are determined during the measurement period ( 37 ).

2 . The method as claimed in claim 1 , wherein the measurement currents (I measure ) are determined by a current measurement apparatus ( 27 ) which is arranged between the specific reference potential ( 17 ) and a driver circuit ( 15 ) which is intended to switch the phase windings ( 12 ) and which is connected to the phase windings ( 12 ).

3 . The method as claimed in claim 1 , wherein the electrical machine ( 11 ) is driven by pulse width modulation signals, wherein, during each measurement window ( 31 , 32 , 33 ), the number of phase windings ( 12 ), which are each connected to the specific reference potential ( 17 ), is different and the remaining phase windings ( 12 ) are each connected to a potential which is different from the specific reference potential.

4 . The method as claimed in claim 3 , wherein a measurement current (I measure ) which corresponds to the field current is determined, depending on whether all phase windings ( 12 ) are connected to the specific reference potential ( 17 ) for a prespecified minimum period of time in an actual measurement period ( 37 ).

5 . The method as claimed in claim 4 , wherein an assessment as to whether a measurement current (I measure ) which corresponds to a field current is measured in the actual measurement period ( 37 ) and is performed on the basis of the instantaneous load on the electrical machine ( 11 ).

6 . The method as claimed in claim 4 or 5 , wherein the electrical machine ( 11 ) has three phase windings ( 12 ), wherein, during each measurement period ( 37 ), a first phase current is measured as measurement current (I measure ) in a first measurement window ( 31 ), and a linear combination of a second phase current with the field current is measured as measurement current (I measure ) in a second measurement window ( 32 ), and wherein a current value of the field current, which current value is measured in a third measurement window ( 33 ), or the stored and/or calculated current value of the field current is used.

7 . An apparatus for determining phase currents through phase windings ( 12 ) and a field current through a field winding ( 13 ) of an electrical machine ( 11 ), in which apparatus a field winding ( 13 ) is connected between a star point ( 14 ) of the phase windings ( 12 ) and a specific reference potential, wherein the apparatus is designed
to determine in each case one measurement current (I measure ) in a plurality of time measurement windows ( 31 , 32 , 33 ) of a measurement period ( 37 ) in an electrical machine ( 11 ) which is periodically driven with a predefined pulse pattern ( 30 ), wherein the measurement currents (I measure ) correspond to currents through one of the phase windings ( 12 ) and through one or more parallel circuits of a plurality of the phase windings ( 12 ); and to determine the phase currents and the field current by evaluating the measurement currents (I measure ) which are determined during the measurement period ( 37 ).

8 . A motor system ( 10 ), comprising:
an electrical machine ( 11 ) with external or hybrid excitation, which electrical machine has a field winding ( 13 ) which is connected between a star point ( 14 ) of the phase windings ( 12 ) and a specific reference potential; a driver circuit ( 15 ) by which electrical energy is supplied to the phase windings ( 12 ) and which supplies current to the phase windings ( 12 ) in accordance with a pulse pattern ( 30 ); a current measurement device ( 24 ) which is arranged between the driver circuit ( 15 ) and the specific reference potential, so that an associated measurement current (I measure ) can be determined in a measurement window ( 31 , 32 , 33 ), said measurement current flowing through one of the phase windings ( 12 ) or a parallel circuit of a plurality of the phase windings ( 12 ) altogether in a corresponding manner with respect to a predetermined current direction; and an apparatus as claimed in claim 7 .

9 . The motor system ( 10 ) as claimed in claim 8 , wherein the driver circuit ( 15 ) comprises an inverter with a bridge circuit.

10 . The motor system ( 10 ) as claimed in claim 8 , wherein a drive unit ( 26 ) is provided in order to generate a plurality of time measurement windows ( 31 , 32 , 33 ) in a measurement period ( 37 ) of the measurement operation by driving the driver circuit ( 15 ) by in each case one or more phase windings ( 12 ) being simultaneously coupled to the connection ( 28 ) of the specific reference potential in accordance with a predefined pulse pattern ( 30 ).

11 . The method as claimed in claim 3 , wherein the pulse width modulation signals are left-aligned.

12 . The method as claimed in claim 3 , wherein the remaining phase windings ( 12 ) are each connected to a supply voltage connection ( 16 ).

13 . The method as claimed in claim 3 , wherein a stored and/or calculated current value is assumed for the field current, depending on whether all phase windings ( 12 ) are connected to the specific reference potential ( 17 ) for a prespecified minimum period of time in an actual measurement period ( 37 ).

14 . The method as claimed in claim 4 , wherein the prespecified minimum period of time in an actual measurement period ( 37 ) is in a time range at the end of a pulse width modulation period ( 38 ).

15 . The method as claimed in claim 6 , wherein the current value of the field current, or the stored and/or calculated current value of the field current is used to determine a third phase current.

16 . The motor system ( 10 ) as claimed in claim 9 , wherein the bridge circuit, is a B6 bridge circuit.

Assignees

• Bosch Gmbh Robert

Inventors

• Lamprecht Dirk

Classifications

• H02P6/32 Primary

  Arrangements for controlling wound field motors, e.g. motors with exciter coils · CPC title

• G01R19/0092 Primary

  Measuring current only · CPC title

• H02M7/53875

  with analogue control of three-phase output · CPC title

• H02M1/0009

  Devices or circuits for detecting current in a converter · CPC title

• H02P21/22

  Current control, e.g. using a current control loop · CPC title