Speed variable inverters for 3 phase squirrel cage induction motors usually
use space vector (sine wave) commutation for obviosly good reasons. Becouse
of small CPU power, I like to try a 6 state trapezoidal commutation as
normally only used for BLDC motor where one phase is always switched off.
The motors are "off the shelf" 3 phase AC induction with output power of 90
Watt (very small & poor efficiency) and 1200 Watt what is also not too big.
Probably the slip will be higher, audible noise appears and torque may go
down becouse of thermal reasons but I have really no idea how much. A speed
range of 1:2 or 1:3 will be sufficient for the application and the variable
frequency is mainly used for soft start with low torque. Any experience
with those unusual constructions? Are the methods also used in small power
white goods like washing mashines ?
16 years ago