inverter duty motors on soft starts 2

[buzzp]

Do inverter duty motors need to be used with soft starts? Thanks

 

[itsmoked]

Negative. Soft starts do not send millions of sharp-edged waveforms into the motor the entire time it's in operation.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[buzzp]

Agreed, but they send some at start-up, albeit not as dramatic. Thanks!

 

[itsmoked]

Actually SSs typically use SCRs that merely gate the line voltage to the motors which is not at all like an IGBT switching full peak line voltage stored on a capacitor bank into a motor. So have at it with your ancient open winding motor. LOL

Keith Cress
kcress -

http://www.flaminsystems.com

 

[jraef]

Keith's right, apples and oranges here. The main risky issue with inverters is the steep rise time of the pulses, typically 0.1 microsecond for 3rd generation IGBTs, newer 4th gen IGBTs are now as fast as 0.01 microsecond, but only a few micro drives are using those yet.

In comparison, SCR turn-on is in the order of 1000 times slower (upward of 100 microseconds), plus they only turn on once per cycle, not 16,000 times per cycle. SCRs are not a problem for the motor...


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[LionelHutz]

Besides the lack of rise time, some inverter duty motors have a torque curve that doesn't work very well with a soft-starter, or any kind of fixed frequency starting method for that matter.