A.C. electric motors

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Ray(in England)
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A.C. electric motors

Post by Ray(in England) » Thu Nov 27, 2003 6:43 pm

Can an A.C. electric motor be made to run from a D.C. supply?.
If so, how?.
Thanks,Ray.

Tom
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Post by Tom » Thu Nov 27, 2003 7:59 pm

either an inverter is needed, or the motor might already have one on, which you take off to get a dc motor? please corect me if i am wrong.
Experience speaks more then hypothesizing ever can. More-so in chemistry.

Mike Kirney
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Never Heard Of That

Post by Mike Kirney » Thu Nov 27, 2003 8:33 pm

I doubt many affordable AC motors have built-in inverters. Even if a motor had an inverter and you removed it, you would still be left with an AC machine. You could run an AC motor from a DC supply by spinning and exciting an alternator field with a DC motor and supply and then using the alternating current generated by that to power your AC motor. This was a common technique in the days before tubes and semi-conductors and mains power.

Ivar
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Post by Ivar » Sat Dec 06, 2003 6:36 pm

Let`s face it:
when you have DC, why on God`s green earth would you want to drive a AC motor with it? And if you *still* want to attempt that meaningless stunt then buy a frequency alternator for an AC engine. It consist of 2 main parts - the power supply that makes AC into DC, then "chopps it up" to simulate AC at the frequency required. If youremove the power supply and connect your battery there (at the needed voltage).
In comparison, a speed\power control systems are most affordable and most efficient for AC motors since they have been developed for a long while now, and provide simplicity in operation and a very, very wide range of speeds, start-effects, stop-slowdowns, anything you want, but if you have DC then converting it back is pretty much a waste.

Bruce
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Post by Bruce » Sat Dec 06, 2003 10:34 pm

It depends on what type of AC motor it is.

Some types (such as the induction motors commonly used for relatively low-power applications such as the water pumps in washing machines) will not work on DC.

Other types, often referred to as "universal motors" will run on either AC or DC.

Of course most commonly used AC motors will require 110 or 220 volts to run so, even if they are a universal type, you can't just whack a 12V battery on them and expect to see much action.

Ray(in England)
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A.C. motor

Post by Ray(in England) » Fri Dec 12, 2003 7:22 pm

Bruce,
So I am wrong to think that a 240 V.Universal motor on 12V. D.C. supply would just turn at 5% of the 240V. rpm?.
So it wouldn't turn at all because it wouldn't have a strong enough electromagnetic field to envelope the rotor?.
Thanks,Ray.

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