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I have an older General Electric 120v DC motor that I need to run on AC?

Just like the title I have a 120 v DC General Electric motor that I want to convert so it will run off 110v AC or basically house current.  I am not a cheapskate but I am on a really tight budget ( alright enough whining).  Thanks

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iceng1 year ago
Plain-DC-Motor.jpg
iceng iceng1 year ago

Great code fix, in good time too !

GaryC61 year ago

I would make a full wave rectifier and add a 200uf cap or so in parallel to the output to just keep down the arcing you may want a snubber diode on that as well. Make your rectifier diodes at least 600v @ 8 to 10 amps as you will a quite high in rush current to start a motor. If you are gong to have a problem that will be it probably but as I said your voltage dc is going to be in the range of 180 V. The output voltage of the rectifier will be Line voltage in RMS times Sqrt of 2. So most U.S. line voltages are actually around 128 volt * sqrt 2 = 181 volts. This may overheat your motor. In which case you may have to do something to regulate the voltage to the motor. it's worth a try. You can add a transistor pass regulator to that but a pulse width modulator line controls a battery drill motor would be better.

dwilson54 (author) 1 year ago

I found a rectifier and will order it later today along with a heat sink. I am using the motor to power a belt driven arbor with grinding and buffing attachments.

GaryC61 year ago

You still haven't said what you are going to use it for. Using a "big dimmer" can work for speed but you loose torque that way. If you are using it for an application where variable speed is not required then required the belt system will work.

Simplest method is probably a big dimmer rated for inductive loads, followed by the recitifer then.

+1

+1

iceng1 year ago

Here is how to wire it with and without dynamic braking.

You don't need a big filter capacitor because of the rotor inertial mass

A small film or ceramic capacitor across the brushes can help quiet brush noise.

DC-Motor.jpgPlain-DC-Motor.jpg
dwilson54 (author) 1 year ago

I could also control speed by various belt placement on a stepped belt pulley I only know basic electrical so any help you give needs to be detailed if possible I am putting together a knife grinding shop and building as many of my tools as I can

GaryC61 year ago

I'll bet you want this for a sewing machine motor don't you. The simplest method would be to use a rectifier capacitor circuit with a sewing machine pedal. However the best way to do it would be to use a pulse width modulated control circuit. My question for that would be are you good with electronic circuit boards and mechanical design? The latter will take some experimenting to get it just right for your application. A "simple" pulse modulation circuit would be a good circuit. The best would be a pulse modulation circuit with feedback. The PWM circuit would slow down and be dependent on human feedback to regulate speed as will be the simple rectifier circuit though I would expect it to have speed problems on the other end. The latter would regulate speed only relative to the pedal control but it's more complicated. I would also recommend if you try and build something you do it from the standpoint of it being a work in progress where you are experimenting to produce your final product. The two pulse width mod circuits would require you to make a foot pedal with a pot in it for the control. How much trouble do you want to go to?

dwilson54 (author)  GaryC61 year ago
no actually using it to run various homemade belt driven machines like grinders and buffers etc
GaryC61 year ago

That would be the rectifier circuit having speed problems on the high end.

GaryC61 year ago

I made the comment about rectifier on wife's computer earlier, please direct info to me.

dwilson54 (author)  GaryC61 year ago
I would like this motor to have speed control if possible I forgot to mention that.
GaryC61 year ago

What will it be used for is a good question as well?

GaryC61 year ago

Is this a brush type motor. Are you wanting speed control or are you just wanting it to run.

The obvious answer to this is a rectifier. However just a rectifier with a capacitor filter will produce about 180V. I need more information to give a complete answer on this. For example how large is this motor? Does it have a horsepower rating? How about a current rating on the information plate? I just happened to sit down at my wife's computer and see this so I will have to look this up on my computer. But I will help if I can.

dwilson54 (author)  gail.d.collins1 year ago

it is 1/4 hp at 2.35 amps according to the plate. I tried to include a picture of the plate in the original post but I guess it didn't take.

GaryC61 year ago

Another question is do you need speed control?

Get a big bridge rectifier, mains rated, and put AC into one side- DC comes out the other.