Intro of VFD

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zahidr1000
Posts: 1
Joined: Mon Sep 24, 2018 2:26 pm

Intro of VFD

Post by zahidr1000 » Mon Sep 24, 2018 2:43 pm

Hi,
In a scenario where there is no power grid available and an electric Generator is needed to power motors.

I have been told that if one wants to run a 20 kw motor from a Generator .The Generator needs to at least produce 60 kw because when a motor is first started it requires three times the power. That is to say at start up the motor requires 3 x 20 kw, hence the need for a 60 kw Generator . There after the motor requires only 20 kw so is only using 20 kw discharged from generator and the rest is wasted.

Is this correct ?

Secondly if one connects the 20 kw motor via a variable frequency drive. Then the motor would be started up gradually using the VFD so would not require 60 kw generator and the same 20 kw motor could be powered by 20 kw - 25 kw producing Generator.

Regards

Zahid

jremington
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Posts: 2321
Joined: Fri Jun 15, 2007 9:41 pm
Location: Eugene, Or

Re: Intro of VFD

Post by jremington » Tue Sep 25, 2018 8:12 am

Most generators are capable of providing for a very temporary overload, like a motor starting. But you should always oversize the power source, so that it is not running continuously at full rated output.

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