do you think we can save electricity in using variable frequency drives?

Answer 1

yes, but only on larger motors.

for examplek, the electricity savings available on a 5HP or smaller motor would not offset the energy consumed to produce the VFD. You may save a few cents on the monthly electric bill but the payback would be long and the net savings of energy to all of society may never be realized.

However, large motors 100 horsepower and larger definitely save energy with VFDs. The torque required to start a motor can be very large. Consider a sump collecting water either from a sewage system or industrial process. Modulating the motor to match the level and inflow into the sump deinitely save elkectricity over letting the sump fill, having the motor turn on and pump it down and then turn off, only to be restarted after the sump fills again. The VFD allows the motor to slow down and speed up and the off-on off cycle can usually be avoided with good engineering.

There is a cut off for when it makes economic sense (the electricity savings will offset the VFD cost) and this can vary. Usually, everyone agrees that % horsepower motors do not warrant the additional expense of a VFD and 100 horsepower and larger do. I know one place that had a cut off to even consider a VFD at 30 HP and above, but I would say between 5 and 100 horsepowe motors should be evaluated on a case by case basis.

Answer 2

yes

Answer 3

No.