short circuit torque

Question

short circuit torque

gaux (Mechanical)

(OP)

11 Feb 09 04:30

I have a asyncronous generator 500 kw and 500 rpm speed, and i´´m designing a fly wheel for it, and the short circuit torque given by the manufacturer is 96 KNm, and i think that maybe is too much... how could i know if this is true..or no so true.... does somebody could help me.... I´´m not very confortable with this questions.... thanks.

dpc (Electrical) · Answer 1 · 2009-02-11 11:32:30

You need to use the value given by the manufacturer, unless you have a lot of liability insurance.

You might ask them to verify, but in the end, you must use their value.

gaux (Mechanical) · Answer 2 · 2009-02-11 11:48:03

but in your opinions, what do you think? is too much?? and why it could be a high value..?
what are the elements that make it to be high? reactance?
thanks

7anoter4 (Electrical) · Answer 3 · 2009-02-12 06:37:58

I agree with dpc you have to follow the Manufacturer indications.
For a very rough appreciation let's take as follows:
Prime motor [DG or wind or else] rated torque as Generator rated torque: Trated= 60*1000/2/PI()*P/rpm=9549.3 Nm.
For a similar induction motor the inertia moment will be J= 60 Kg.m^2.Let's say the prime motor has the same inertia moment.
Let's suppose, up to generator breaker will trip time=0.07 sec and within this time the generator will positively stop.
The possible torque on the Generator shaft will be Te=(Jgen+Jmot)dw/dt+Trated
dw=(2*pi*rpm/60-0)= 52.36 rot/sec
Te=2*60*52.36/.07+9549.3=102000 Nm=102 kNm.

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