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ab72756
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Join Date: Apr 2008
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a/c-d/c electric motor

05/25/2008 8:17 AM

Is it possible for an electric motor to run on either A/C or D/C.

Also:

I have an old electric motor (132v. D/C) that has external connections for both the armature windings and the field windings. What is the best way to connect controls to regulate speed and power.
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JRaef
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#1

Re: a/c-d/c electric motor

05/25/2008 2:04 PM

There is a type of motor design called a "Universal Motor" which will accept an AC or DC supply. Technically, it is a DC motor design modified to rectify the DC to AC at the point of use. Hand power tools and small appliances use this type of motor. But this is a very specific motor design. You cannot intermix AC and DC in motors as a rule.

As to your existing motor motor connections, it is best to check with the manufacturer f possible. There are quasi-standards for connections, but not everyone goes by them. But just in case, here is a chart on the mot common connections.

http://www.usmotors.com/Products/DC/2286.pdf

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Sparkstation
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#4
In reply to #1

Re: a/c-d/c electric motor

05/26/2008 9:30 PM

Hello JRaef

from me for that.

Kind Regards....

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Bill
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#2

Re: a/c-d/c electric motor

05/26/2008 2:22 PM

Yes. A universal motor runs on both AC and DC. The motor is a brush type with a field stator that is excited by AC or DC, and the rotating armature of the motor is excited by AC or DC, respectively, (it is not rectified by any means). The rotor follows the rotating field of the stator.

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garth
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#3

Re: a/c-d/c electric motor

05/26/2008 8:38 PM

I would suspect your 132 Volt motor has a shunt winding as well as a series winding. The shunt winding is not suitable for AC operation and the series winding would not be large enough to give a reasonable output of power. If the motor were connected to AC with shunt field disconnected it would probably overspeed and damage itself.

The best way to operate the DC motor with AC is to fit a suitably rated bridge rectifier in circuit and operate it as it was meant to

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Sparkstation
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#5
In reply to #3

Re: a/c-d/c electric motor

05/26/2008 9:32 PM

Hello garth

from me for that.

Kind Regards....

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#6
In reply to #3

Re: a/c-d/c electric motor

05/26/2008 11:31 PM

garth; universal motors mean ac-dc,that means they will run on 25 to 60 hz & DC perry
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garth
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#7
In reply to #6

Re: a/c-d/c electric motor

05/27/2008 8:02 PM

I did not see any reference to a universal motor in the original post. What was your point?

Also by way of a follow up now I am posting again, to vary the speed with a DC supply you can feed the shunt winding with a variable voltage, or the armature within the ratings of the motor the output power will depend on which combination you choose.

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Anonymous Poster
#8

Re: a/c-d/c electric motor

05/28/2008 3:40 AM

the application is very important

dc motor is used when u need to control starting current and regulate speed , but they are suffering from some problems like brushes and commutator, spark, carbonate..

the best way is to use ac motor with frequency converter which is now very simple and cheep. where you can control the speed and starting current smoothly without any headache about brushes and sparks.
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