All:
I have a few questions about VSD’s that is the result of reading other threads referring to motors needing to be VSD rated. I have not worked with drives in several years and realize that the technology has changed. Please correct me with my outdated assumptions.
I have seen several references to the output voltage being 1.414 higher than the output RMS volts. In the past with PWM type drives the actual overshoot would be in the order of 3 to 4 times the bus voltage at the time of the semi-conductor switching. Even then to get numbers that low you would need an extremely well designed drive. The only way to prevent this overshoot was to build an elaborate capacitor filter to be placed between the drive and the motor. In simple terms this overshoot would literally try to shoot holes in not only the motor insulation, but the cable insulation too.
Q:
Has drive technology improved enough that the expected overshoot is not that high?
The other point about using “inverter duty motors” was the expected vibration or mechanical stress on the motor winding themselves that was caused by the constant switching or pulses.
Q:
Do VSD rated motors have additional blocking on the windings to prevent them from moving (walking) during inverter operation?
Old technology was that the pulses from a PWM drive would try to shoot holes in the insulation of both motors and cable.
Q:
Were there ever any recommendations about upgrading the cable insulation on the output of a VSD?
Once again I am very far removed from the drive industry. It is my understanding that drives are now operating with a sinusoidal output. The idea of operating a transistor in a linear fashion is amassing. Heat dissipation must be a big problem.
Q:
Are drives being made that can do that? If so what type transistor is being used? With a drive like this do you need a VSD rated motor?
Thanks for any input you may offer.
David
I have a few questions about VSD’s that is the result of reading other threads referring to motors needing to be VSD rated. I have not worked with drives in several years and realize that the technology has changed. Please correct me with my outdated assumptions.
I have seen several references to the output voltage being 1.414 higher than the output RMS volts. In the past with PWM type drives the actual overshoot would be in the order of 3 to 4 times the bus voltage at the time of the semi-conductor switching. Even then to get numbers that low you would need an extremely well designed drive. The only way to prevent this overshoot was to build an elaborate capacitor filter to be placed between the drive and the motor. In simple terms this overshoot would literally try to shoot holes in not only the motor insulation, but the cable insulation too.
Q:
Has drive technology improved enough that the expected overshoot is not that high?
The other point about using “inverter duty motors” was the expected vibration or mechanical stress on the motor winding themselves that was caused by the constant switching or pulses.
Q:
Do VSD rated motors have additional blocking on the windings to prevent them from moving (walking) during inverter operation?
Old technology was that the pulses from a PWM drive would try to shoot holes in the insulation of both motors and cable.
Q:
Were there ever any recommendations about upgrading the cable insulation on the output of a VSD?
Once again I am very far removed from the drive industry. It is my understanding that drives are now operating with a sinusoidal output. The idea of operating a transistor in a linear fashion is amassing. Heat dissipation must be a big problem.
Q:
Are drives being made that can do that? If so what type transistor is being used? With a drive like this do you need a VSD rated motor?
Thanks for any input you may offer.
David
