Help: Mains Powered DC Motor - Electronic Circuits Projects Diagrams Free

bobledoux · 1st October 2007, 05:27 PM

I’m looking for some help with 120 volt DC motor control.

I want to power a micro lathe with this American Bosch 120 volt DC, 5.5 amp permanent magnet motor:

http://www.surpluscenter.com/item.as...tname=electric

I’ve been told I could use a bridge rectifier through my autotransformer to provide variable speed.

Would the small controllers intended for 90/180 volt DC motors also work for this application?

Would a dimmer switch through a rectifier also work?

Do I have to ramp up the voltage when starting the motor?

Are there other variable speed control options?

Sceadwian · 1st October 2007, 11:52 PM

There are many options for driving DC motors with variable speed control, more than you'll likley every want to know about. I like the autotransformer and bridge rectifier sollution though, it's very simple and would be very reliable if you properly over rate the diodes. The inductance/intertia of the motor will do some smoothing itself but you still may get 120hz pulsations without capacitors to filter the output. A dimmer switch will work if you can find one rated for the current, but it's output is pretty rough so the filtering requirements are going to be higher.

bobledoux · 2nd October 2007, 01:28 PM

I'm considering a PIC controlled PWM motor control. In the past I've used transistor switches for low voltage applications. What is the mechanism for switching high current DC at over 100 volts?

stevez · 2nd October 2007, 08:50 PM

I have several Baldor 90 dvc motors with controllers - maybe 1/2 hp or so each. The controllers appear to be very basic but I am told they are effective in maintaining reasonable control of RPM with varying loads. I've looked thru catalogs (McMaster Carr or Grainger I think) and see that these controllers are not all that expensive. I've also seen just the control boards from places like Jameco - maybe even kits.

Keep in mind that varying the voltage to a DC motor will adjust the speed. Without some kind of feedback there really is no control - and the speed will vary considerably in some instances as the load changes.

The plan for my motor - power my Craftsman/Atlas bench top lathe.

Hero999 · 10th October 2007, 09:30 PM

You should be able to power a 120VDC PM motor from 120VAC using a bridge rectifier without any problems.

If you want to add variable speed controll then just use a lamp dimmer before the rectifier.

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1st October 2007, 05:27 PM	(permalink)
bobledoux	Help: Mains Powered DC Motor I’m looking for some help with 120 volt DC motor control. I want to power a micro lathe with this American Bosch 120 volt DC, 5.5 amp permanent magnet motor: http://www.surpluscenter.com/item.as...tname=electric I’ve been told I could use a bridge rectifier through my autotransformer to provide variable speed. Would the small controllers intended for 90/180 volt DC motors also work for this application? Would a dimmer switch through a rectifier also work? Do I have to ramp up the voltage when starting the motor? Are there other variable speed control options?

1st October 2007, 11:52 PM	(permalink)
Sceadwian	There are many options for driving DC motors with variable speed control, more than you'll likley every want to know about. I like the autotransformer and bridge rectifier sollution though, it's very simple and would be very reliable if you properly over rate the diodes. The inductance/intertia of the motor will do some smoothing itself but you still may get 120hz pulsations without capacitors to filter the output. A dimmer switch will work if you can find one rated for the current, but it's output is pretty rough so the filtering requirements are going to be higher. __________________ "Because I be what I be. I would tell you what you want to know if I could, mum, but I be a cat, and no cat anywhere ever gave anyone a straight answer, har har."

2nd October 2007, 01:28 PM	(permalink)
bobledoux	I'm considering a PIC controlled PWM motor control. In the past I've used transistor switches for low voltage applications. What is the mechanism for switching high current DC at over 100 volts?

2nd October 2007, 08:50 PM	(permalink)
stevez	I have several Baldor 90 dvc motors with controllers - maybe 1/2 hp or so each. The controllers appear to be very basic but I am told they are effective in maintaining reasonable control of RPM with varying loads. I've looked thru catalogs (McMaster Carr or Grainger I think) and see that these controllers are not all that expensive. I've also seen just the control boards from places like Jameco - maybe even kits. Keep in mind that varying the voltage to a DC motor will adjust the speed. Without some kind of feedback there really is no control - and the speed will vary considerably in some instances as the load changes. The plan for my motor - power my Craftsman/Atlas bench top lathe. __________________ stevez

10th October 2007, 09:30 PM	(permalink)
Hero999	You should be able to power a 120VDC PM motor from 120VAC using a bridge rectifier without any problems. If you want to add variable speed controll then just use a lamp dimmer before the rectifier. __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez