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Eliminating damper for slip ring motor


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#1 ram14375

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Posted 11 June 2006 - 03:56 AM

Dear sir,
We have got a 2650 kw 11kv /rotor voltage 1425 rotor current 1125 /1000 rpmslip ring motor used for fan application.we are varying the speed from 600 rpm to rated speed(994) with the grid resistances.

The resistance values are 0.09/0.18/0.36/0.72/1.44 connected in delta across the rotor.
While starting we close the damper at the inlet of the fan and start it at 600 rpm.We wanted to removed this damper as this is causing some pressure drop .

whether this damper can be removed and the motor be started at the same speed(600 rpm).how will be the impact of starting current.

Thanks
ram

#2 marke

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Posted 11 June 2006 - 06:25 AM

Hello ram14375

Welcome to the forum

I would expect that if you remove the damper and start in the same manner as you do now, there will not be a major problem. You may find that the fan takes longer to start with reduced acceleration as it approaches 600RPM due to the increased load.
Note. The damper will only have an effect where the fan is beginning to move a significant amount of air. This will not be an issue at very low speeds.

The big question would be, can the equipment and supply withstand a longer starting time??

Best regards,

#3 mariomaggi

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Posted 11 June 2006 - 10:01 AM

Dear ram14375,
I'm surprised to read how many losses in kW you have at reduced speed!

Do you evaluated the possibility to recover such energy using another converter instead of resistors?
Probably you can save such energy, using the same for a non-critical application or resending the energy on a low-voltage bus bars.

Regards
Mario

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