AC Motor Control and EV Applications

PMSM High-Speed Operation

Chapter 7

Single-Pole Section of PMSM

Air Gap Electromagnetic PowerElectric Loading

Air gap power

Torque

Rotor

Torque is proportional to the rotor volume.

Magnetic and Electric Loadings

Motor Speed Selection

Torque

Speed

Torque

Speed

Same Power

HighStartingTorque Low

StartingTorque

Motor I Motor II

Larger Volume Smaller Volume

• Torque is proportional to current ( T= k I ).• Since max. current loading is utilized, higher current implies larger volume.

Under the same power condition, high speed motor has smaller volume.

Reduction Gear

Current and Voltage Vectors

d axis

q axis

d axis

q axis

Voltage limits

Voltage Limits versus Speeds

q-axis

d-axis

Current limit

Voltage limits

x x

x

Speedincrease

x

q-axis

d-axis

Current limit

x

(a) (b)

Voltage Limit

Power

Speed

-if

Voltage limits

max

q-axisCurrent limit

d-axis

Power

Speed

-if

Voltage limits q-axis

Current limit

d-axis

Power

Speed

-if

Voltage limits q-axis

Current limit

d-axis

(a) (b) (c)

Power Profile Depending on Ld Is and m

Voltage and Current Angles

Magnetic and Reluctance Torques vs

Maximum Torque Per Ampere

MTPAcontour

ide

iqe

Constantcurrent

contoursConstant

torquecurves

MTPA (Different Derivation)

Current limits

Constanttorquecurves

ide

iqe

Maximum Power Control

Maximum Torque/Flux Control

Constantflux curves

Max. torque/flux

Combination of Control Methods

Max. power

3200rpm

7600rpm

10200rpm20000rpm C

Max. torque/flux

MTPA

Current limit

=2600rpmA

B

O

=8Nm

=4Nm

Example Motor

Power, Torque, Currents, and Current Angle

Continued Example

Unity Power Factor Control

Unity PF for

Exercise 7.2

d axis

q axis

34A

-22A

-54.8V

-172V

77.5V

173.5V 82.5o

32.9o

Power and PF vs PM Strength

Per Unit Model of PMSM

[pu]2 4 6 8

IPMSM-A

IPMSM-B

Normalized Power Curves (Exercise 7.6)

EV Motor Example