low voltage high frequency drives
low voltage high frequency drives
(OP)
I am using variable frequency drives for altering the speed of a 3 phase motor. As frequency is increased from 50 to 150 hz, my 2 pole motor attains 9000 rpm. Now i wish to use the same drive for low voltage 3 ph motor. can the output from a VFD be fed to a step down transformer for reducing the voltage from 415 v to 50 v.Can someone provide me with a standard circuit for such an arrangement. my motor runs on 50 volts 3ph ~ suppply of 150 hz, capacity 1.5 KW.





RE: low voltage high frequency drives
you will need to take the extra heating of the vfd's pwm into account when sizing it. If you are in the USA I would be happy to quote you just such a transformer.
RE: low voltage high frequency drives
RE: low voltage high frequency drives
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: low voltage high frequency drives
What is the application of the low voltage high speed drive ? The low voltage might have been chosen due to especially restrictive safety concerns.
RE: low voltage high frequency drives
RE: low voltage high frequency drives
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: low voltage high frequency drives
We have never used an isolation transformer ("2 winding transformer") on output of a vfd as theoretically it is a bad idea: from 0 to prob around 30+hz its output would be zero, so you would be basically applying 1/2 motor voltage instantly to the motor, which will result in the normal 600% current draw, causing the vfd to simply shut down on ourput overcurrent. But ok by me for someone to try it. If you do try it, please report back how it works.
These reasons are why only autoxfmrs are used on output of vfd drives: dc thru the max freq go thru just fine and don't mess up the v/hz ratio.
RE: low voltage high frequency drives
http://www.boschproductiontools.com/productionstoo...
You will also find the safety/low voltage issue beeing discussed there.
Beside the rotating equipment described in the catalog there are also inverters available specifically for this purpose. Of course it is tempting to apply a standard drives inverter for this purpose because of cost, but going with speciallized equipment looks more appropriate to me unless you are a specialist on this application yourself. The low voltage approach for safety is only viable if you provide isolation from the mains.
RE: low voltage high frequency drives