Multiphase motor winding topology and control

Details Multiphase motor winding topology and control Multiphase motor winding topology and control

2003-09-10

2004-09-14

Mullins, Burton (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S071000, C310S179000, C310S180000, C310S254100, C318S254100

Reexamination Certificate

active

06791226

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to rotary electric motors, more particularly to winding circuit configurations for motors having a plurality of phases and the control of a multiphase motor using a minimum number of control states.
BACKGROUND
The above-identified copending patent applications describe the challenges of developing efficient electric motor drives for vehicles, as a viable alternative to combustion engines. Electronically controlled pulsed energization of windings of motors offers the prospect of more flexible management of motor characteristics. By control of pulse width, duty cycle, and switched application of a battery source to appropriate stator windings, superior functional versatility can be achieved. In many motor applications, a vehicle drive environment is but one example, it is highly desirable to attain smooth operation over a wide speed range, while maintaining a high torque output capability and conserving the power source.
Motor structural arrangements described in the identified copending applications contribute to these objectives. Electromagnet core segments may be configured as isolated magnetically permeable structures in an annular ring to provide increased flux concentration. Isolation of the electromagnet core segments permits individual concentration of flux in the magnetic cores, with a minimum of flux loss or deleterious transformer interference effects with other electromagnet members.
FIG. 1
is an exemplary view showing rotor and stator elements of a motor such as disclosed in the copending application Ser. No. 09/826,422, the disclosure of which has been incorporated herein. Rotor member
10
is an annular ring structure having permanent magnets
12
substantially evenly distributed along cylindrical back plate
14
. The permanent magnets are rotor poles that alternate in magnetic polarity along the inner periphery of the annular ring. The back plate may comprise magnetically permeable material that serves as a magnetic return path between adjacent permanent magnetic poles
12
. The rotor surrounds a stator member
20
, the rotor and stator members being separated by an annular radial air gap. Stator
20
comprises a plurality of electromagnet core segments of uniform construction that are evenly distributed along the air gap. Each core segment comprises a generally u-shaped magnetic structure
24
that forms two poles having surfaces
26
facing the air gap. The legs of the pole pairs are wound with windings
28
. Alternatively, the core segment may be constructed to accommodate a single winding formed on a portion linking the pole pair. Each stator electromagnet core structure is separate, and magnetically isolated, from adjacent stator core elements. The stator elements
24
are secured to a non magnetically permeable support structure (not illustrated), thereby forming an annular ring configuration. This configuration eliminates emanation of stray transformer flux effects from adjacent stator pole groups.
The above-identified application Ser. No. 10/173,610 describes motor control strategies contemplated for precise controlled performance for various applications of such motors. While typical control systems assume uniformity of parameter values over the entire motor, it is recognized in that application that provision of independent structural elements may cause variance of circuit parameters, such as phase resistance, phase self-inductance and the like, among the various stator elements. Motor control thus involves the fusion of nonlinear feedforward compensation coupled with current feedback elements. Each stator core segment is individually controlled as a separate phase, each set of phase windings energized in response to control signals generated by a controller in accordance with the set of control parameters associated with the stator phase component for the phase winding energized. In the exemplified seven phase motor illustrated, active control is required individually for all seven states.
Control according to application Ser. No. 10/173,610 is illustrated in
FIGS. 2 and 3
. The stator phase windings are switchably energized by driving current supplied from d-c power source
40
via electronic switch sets
42
. The switch sets are coupled to controller
44
via gate drivers
46
. Controller
44
has one or more user inputs and a plurality of inputs for motor conditions sensed during operation. Current in each phase winding is sensed by a respective one of a plurality of current sensors
48
whose outputs are provided to controller
44
. The controller may have a plurality of inputs for this purpose or, in the alternative, signals from the current sensors may be multiplexed and connected to a single controller input. Rotor position sensor
46
is connected to another input of controller
44
to provide position signals thereto. The output of the position sensor is also applied to speed approximator
50
, which converts the position signals to speed signals to be applied to another input of controller
44
.
The sequence controller may comprise a microprocessor or equivalent microcontroller, such as Texas Instrument digital signal processor TMS320LF2407APG. The switch sets may comprise a plurality of MOSFET H-Bridges, such as International Rectifier IRFIZ48N-ND. The gate driver may comprise Intersil MOSFET gate driver HIP4082IB. The position sensor may comprise any known sensing means, such as a Hall effect devices (Allegro Microsystems 92B5308), giant magneto resistive (GMR) sensors, capacitive rotary sensors, reed switches, pulse wire sensors including amorphous sensors, resolvers, optical sensors and the like. Hall effect current sensors, such as F. W. Bell SM-15, may be utilized for currents sensors
48
. The speed detector
50
provides an approximation of the time derivative of the sensed position signals.
FIG. 3
is a partial circuit diagram of a switch set and driver for an individual stator core segment winding. Stator phase winding
28
is connected in a bridge circuit of four FETs. Any of various known electronic switching elements may be used for directing driving current in the appropriate direction to stator winding
28
such as, for example, bipolar transistors. FET
53
and FET
55
are connected in series across the power source, as are FET
54
and FET
56
. Stator winding
28
is connected between the connection nodes of the two series FET circuits. Gate driver
46
is responsive to control signals received from the sequence controller
44
to apply activation signals to the gate terminals of the FETs. FETs
53
and
56
are concurrently activated for motor current flow in one direction. For current flow in the reverse direction, FETs
54
and
55
are concurrently activated. Gate driver
46
alternatively may be integrated in sequence controller
44
.
The particular circuitry shown and described above is merely representative of various alternative motor energization circuitry. However, each phase has associated switching and driver circuitry that permits active control of each phase state. For motors having a large number of phases, the duplication of such circuitry for each phase and the increased complexity of circuit real estate and functionality becomes expensive and burdensome. The need thus exists for effective control of a motor having a large number of phases while reducing the number or controllable states.
DISCLOSURE OF THE INVENTION
The present invention fulfills this need, while maintaining the benefits of the separated and ferromagnetically isolated individual stator core element configurations such as disclosed in the copending applications. A reduced number of controllable states is achieved while retaining a high degree of precision controllability.
Advantages are achieved with a multiphase brushless permanent magnet motor having a stator provided with at least one winding for each phase, the windings permanently connected to each other at a plurality of junctions. A power source is coupled, via controlled motor energization circuitry, to a plurality of terminals

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