# how to replace dc motor with ac motor power calculation



## waff (Mar 30, 2016)

correction the voltage rating is 440 volts dc


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## joebanana (Dec 21, 2010)

If you have, oh...lets say a 100hp. DC motor, you'd probably want a 100hp AC replacement motor. Plus the transformer, and motor starter, and conductors to match.


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## JRaef (Mar 23, 2009)

kW is kW, so you could theoretically replace it with a 315kW AC motor. But the speed/torque profile of a DC motor can be vastly different than an AC motor. Is theDC controller a Variable Speed Drive or just on-off control? That might make all of the difference.


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## telsa (May 22, 2015)

A DC motor at that scale spells traction -- either in rolling stock (locomotives) -- or in a steel rolling mill.

In which case you need to consult EEs with expertise in the matter.

It's a BIG decision.


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## triden (Jun 13, 2012)

My guess it's a big hoist motor. Nevertheless, any big drive/motor company would be willing to spec out the equipment for you to make the sale.


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## waff (Mar 30, 2016)

JRaef said:


> kW is kW, so you could theoretically replace it with a 315kW AC motor. But the speed/torque profile of a DC motor can be vastly different than an AC motor. Is theDC controller a Variable Speed Drive or just on-off control? That might make all of the difference.




the dc motor is driven by dc drive manufactured by parker


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## John Valdes (May 17, 2007)

First thing first. Torque! Match the torque of the dc motor and you should be good.
The manufacture or distributor would love to assist you in this.


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## mitch65 (Mar 26, 2015)

Manufacturer or vendor of the equipment being driven should be able to help you out if they still exist.


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## JRaef (Mar 23, 2009)

John Valdes said:


> First thing first. Torque! Match the torque of the dc motor and you should be good.
> The manufacture or distributor would love to assist you in this.


Yes, that's why I said the torque PROFILE is important, but you are right, I was not taking into account the likely differences in base speed. The AC motor torque is based on final speed, the DC motor torque can be, depending on design, constant throughout the speed range. This means the DC drive and motor is likely more capable of low speed torque _and _response to step changes in load than what most AC drives and motors can provide. That's not to say it can't be duplicated, but you have to be careful with how you approach it.

315KW = 422.25HP, at 1440RPM = 1539 lb. ft. of torque.
*500HP* AC motor at _1725_RPM = 1521 lb. ft. of torque, but only at full speed or with a VERY good Flux Vector VFD at any speed.


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## oliquir (Jan 13, 2011)

he is in india so probalby a 50hz base motor so rpm is quite the same


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