Air Gap Electromagnetic PowerElectric Loading
Air gap power
Torque
Rotor
Torque is proportional to the rotor volume.
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
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
Combination of Control Methods
Max. power
3200rpm
7600rpm
10200rpm20000rpm C
Max. torque/flux
MTPA
Current limit
=2600rpmA
B
O
=8Nm
=4Nm
Example Motor