Freewheeling motor 1

[bush600]

I am installing a crusher with 2 X 75HP 460V 3PH drive motors.
Machine is belt driven.
As we are not at full capacity the plan is just to power one drive motor. This will mean the unpowered motor will freewheel at 1760 rpm..
Should I short out the undriven motor windings or just leave unconnected? Thanks.
Gordie Forrest

 

[davidbeach]

Leave unconnected. You'll gain nothing by shorting the leads.

 

[waross]

What David said!

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[jraef]

AC induction motors only regenerate when the windings are excited, usually by the line power. But even then, only when driven FASTER than their base synchronous speed. In your situation you have neither condition.

"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
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[electricpete]

There will be some small residual voltage associated with iron Br and dependent upon the deenergization transient. When I do phase rotation test, I often see it about 100 millivolts spinning at 100 rpm. With 1800 rpm motor that could mean around 1.8 volts at full speed, open-circuit condition.

With leads shorted, I'm not sure what results would be.
Safest thing, just leave the leads open as said above.

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(2B)+(2B)' ?

 

[electricpete]

I imagine leaving the circuit open is also the easier option... just involves opening a single contactor. Shorting would require a more complicated setup which isn't required and might possibly (not sure) have some adverse consequences.

Sorry if I am repeating the obvious for other posters.

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(2B)+(2B)' ?