Online assistance for electrical trade people Login  |  Register  |   Forgot Password
Assistance for electrical trade people




Click here to send Ron a pdf document for publication on this Topic

Documents must be less than 200k in pdf format

Posted By Topic: VSD

Apr 04 2013 21:20

Put a VSD on 0.37Kw motor in order to increase its speed for a specific operation. The frequency was increased from 50 to 80Hz to aquire the desired speed. Why did the motor open circuit after only 2 days of operation?

Angry Client
Apr 04 2013 21:36

I once had a some equipment that I ran at 160% of it's rated capacity (due to demands of the market) and I too was surprised that it only lasted a matter of hours.

Dam filthy, cheaply constructed, imported crap!!

Can't wait to see some of the replies on this one! Bring it on electrical experts!

Apr 04 2013 22:18

Prob due to the rating if the motor, its rated for 50hz, not 80. If u increase the hz then u take it past what it us rated for. A motor is rated for a certain hz, if u go above that, then u will reduce the toeque of the motor, so will draw more curry than its ment to fir the given load. Most motors will have a max % u can increase without damage but their is limits. Get another motor with less polls,and reduce it rather than increase it.

Apr 05 2013 20:23

If this was a application which required a "fixed" speed in excess of the motors nominal speed, wouldn't a gearbox been a better way to achieve it?


Apr 06 2013 13:12

which is also why it's often not OK to run American 60 Hz gear at our 50Hz supply; the motor is 20 % slower and may not get sufficient cooling.

There are motors designed for over-speed by increased frequency, talk to a reputable motor suppler. But it'll be expensive.

Horses for courses.
VSDs are for varying speed situations, not constant speed.
For start-current reduction, use a soft-starter

And if you just want high speed, use pulleys / gearbox and a standard motor.

Especially with such a small motor, should be easy, and much cheaper than the VSD option