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Associate

Join Date: May 2011
Posts: 38

VFD Selection

05/20/2011 8:33 AM

Dear friends ,

My system voltage is 380v/3ph/60hz & one of the motor rating is 7.5kW/3ph/50hz , I need to install a motor on 50hz for system voltage of 60hz .Is it better to select a VFD where we can make setting in the VFD from 60hz to VFD.

Is it right way to select the VFD.

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Guru
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#1

Re: VFD Selection

05/20/2011 11:08 AM

The right way is to specify the correct motor / drive arrangement.

Why pay for all the equipment and aggravation when a bit of forethought would have given a simple solution.

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Guru
United States - Member - New Member Engineering Fields - Power Engineering - New Member

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#2

Re: VFD Selection

05/20/2011 12:56 PM

Assuming that you had no choice in the initial selection and are the person responsible for making it work now, yes a VFD will probably solve your problem. But you did not state the VOLTAGE rating of the motor, only the kW and Hz. ASSUMING it is also 380V (or anywhere from 380-415V), then you would simply program your VFD with that motor nameplate data and tell it that it's maximum output is 50Hz at 380V. The VFD does not care what the incoming frequency is, all it does is rectify it to DC anyway.

If you need for your motor to run at 60Hz however, then you have a problem. Your V/Hz ratio will be deficient and you will lose torque as the speed is increased above the base design speed. Depending on your application this may or may not be a problem, motors are sometimes over sized anyway. If it is a problem, you will need to increase the input voltage to a commensurate level to maintain the original design V/Hz ratio of 7.6:1, so 7.6 x 60Hz = approx. 460V. These are relatively common transformers.

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