115 shunt wound motor pwm circuit. Where to start?

Thread Starter

Hamlet

Joined Jun 10, 2015
519
I doubt that those motors could care less about ripple. I've seen similar general purpose type DC motors like those used on some pretty crude DC power supplies that ran for years in near continuous use without issues.

Given their low amp ratings I would just use a simple light dimmer unit ahead of a bridge rectifier and a large capacitor for the power supply. I've got several DC motors I run like that in variable speed applications that work just fine.
Experience counts. Thanks.

I used a light 600w triac dimmer ahead of bridge rectifier for testing, but the dimmer eventually died. The uF value of cap I was using at the time
was small.
 

Thread Starter

Hamlet

Joined Jun 10, 2015
519
I just did a test with a bridge rectifier to mains, a cap of 1uF/500v, and 3.5Amps of resistive load.
The d.c. voltage was 158v under load. I'll try a dimmer from my junk box again, and then load
test with the motor.
 

tcmtech

Joined Nov 4, 2013
2,867
The motors I have set up that way I used around 100 uf or more per amp of their rating and the dimmer were the rotary type the shut off when turned opposed to th epush on/off type that can supply full power when switched on.

The rotary on/off type work well as automatic soft start units being they are always switching on at their minimal output point.
 

tcmtech

Joined Nov 4, 2013
2,867
Then you may want to use a heavy duty type dimmer (1000 - 1500 watt) or ceiling fan speed controller unit ahead of the rectifier. They will take the inrush current spikes much better than the 600 watt rated dimmers can.
 

Thread Starter

Hamlet

Joined Jun 10, 2015
519
Then you may want to use a heavy duty type dimmer (1000 - 1500 watt) or ceiling fan speed controller unit ahead of the rectifier. They will take the inrush current spikes much better than the 600 watt rated dimmers can.
Difficult to find a 1000w unit on ebay that doesn't specifically exclude anything but incandescent or halogen lighting. Fan dimmers are 1.5A to about 5A. 600w dimmers are very common, and maybe those would work better with a diode on the motor for EMF.

I think my best bet is to control the d.c. after the rectifier, rather than the other way around.

I did find this router control,

http://www.ebay.com/itm/131662809948?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT
 

tcmtech

Joined Nov 4, 2013
2,867
None of the light dimmers I have ever used were rated for anything but incandescent or halogen bulbs but they still worked just fine as speed controllers for DC motors.

To be honest the speed control trigger in power tools is not really any different than a light dimmer. Just more compact and capable of handling higher power. That router controller is basically the same thing in an external box. ;)

The other option for making variable DC voltage from an AC source to run a motor is to use a Variac transformer instead of a phase angle control system.

If you are looking for off the shelf pre-built plug and play units just search eBay or Amazon for '90 DC motor control'. you will find loads of them that are for running higher voltage variable speed DC motors from regular AC line power.
 

MaxHeadRoom

Joined Jul 18, 2013
28,619
I did find this router control,
Those are Triac control aimed primarily at Universal motor control, the fact they claim for DC motor also implies a bridge after the Triac.
The advantage with the KB controllers, both SCR and PWM is they have accel/decel/speed limit adjustment and current regulation.
Max.
 
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