AC to DC motor Contoller

[JohnC]

I have several 90VDC, 1/4 hp, 2.6 amp PM motors kicking around.

My plan is to use one for testing windmill projects and such.

What I am in need of is a circuit that will convert 110 AC  to 90 volts DC with a varible speed control of the rpm. In addition to this I would like measure the rpm.

Would greatly appreciate any help with this design.

[wdyasq]

OPTIONS:

Buy one - they are not expensive.

Search - Learn to use a search engine - there are many designs on the internet.

Ron

[HomegrownPower]

wdyasq

I think this will help you . You will still need something to control speed . Nut this ebay iten should do your ac to DC switching ( I think ) Ebay item number 190163973809 for a whopping $7.99 and $4 something to ship ?

This is what it says about it

THESE SUPPLIES ARE JUST UNDER 8 OUNCES, YET PROVIDE A MULTIPLE OUTPUT AT:

5VDC @ 6 AMPS
+12VDC @ 3.6 AMPS
-12VDC @ 0.5 AMPS
THE INPUT IS VERSATILE, 100-240VAC @ 50-60Hz, AND IS AUTOMATIC.

THESE ARE 3 INCHES BY 5 INCHES AND ARE ABOUT AN INCH THICK.


PowDec

Model # PTE43-31

Hope that helps things some

Lonnie

[dbcollen]

since you need 90vdc I would use a variac and a full wave bridge rectifier. You can dial the variac for whatever voltage you want, and the rectifier will convert the output to DC. you will need 63 volts AC to get 90 Volts DC, a capacitor on the output will smooth out the ripple from the single phase ac. Here is one

http://cgi.ebay.com/Metered-Variac-Var-AC-Output-Transformer-5-Amp-NEW_W0QQitemZ320172453519QQihZ011
QQcategoryZ1504QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Dustin

[Goose]

Good quick response Wdysaq!  I'm sure everyone likes reading your colorful responses!  I'll keep the rest of my words towards you to myself.

JohnC

I too would be intererested in the replys you get.  

Personally I use a drive by KB Electronics, the model is KBIC-120.  If you keep an eye on Ebay you can find these things cheap, and you can get your variable speed with them.  If you need to get 180VDC they make a model KBRG.  They have a website where you can find the model that will work for you.

I thought about getting a variac and rectify, but these drives make it cheaper and easier.

[JohnC]

Thanks for your input, any help is appreciated.  This is why I like this group.

I was thinking, (dangerous at times) if I could use a 110V AC light dimmer switch and hook this up to a bridge rectifier. My thoughts would be the switch would get too hot.

THX

[Slingshot]

John,

Cheap light dimmers work by modulating the duty cycle, not the amplitude, of the input AC.  In order to use one of these safely as a variable DC supply you would need to run the output of your rectifier bridge through an inductor-input low-pass filter.  This will convert the duty-cycle-modulated rectifier output to an average DC value.

[Phil Timmons]

It has been a while since Circuits -- but I think the math is that 120 VAC gives about 90 VDC.  (120 * .707 = 84)  The marginally higher rating of 90 VDC the industrial motors all use is to allow the 120 VAC to be a little "hot" -- up to nearly 130 VAC without passing the rating of the DC motor.  

At anyrate, use a variac to vary the AC, hit the output with a rectifier (smoothing capacitor optional) and you have a typical 90 VDC drive circuit that is used in common industrial applications such as variable speed conveyors.  

Need a picture drawn?  No biggie, just say so.  

[Drives]

This is to cool!  Here we are talking about DC drives, I look to the right, and see a Google advertisement for my company!  Sorry, I just had to mention this.

Goose is on the right track, use a SCR DC motor drive.  KB is one of many brands.

The SCR DC motor drive has a built in current limit circuit, speed regulation, IR compensation, uses a potentiometer for speed command, simple switch for run/stop  command, etc, etc.  

The Variac, and light dimmers aren't used in industrial applications because they do not protect the motor, do not provide good speed regulation, and require breaking line current vs. just shutting off the SCR's gate pulse.  The Variac will work, but I wouldn't use it.

In short, the SCR DC motor drive has been around since the SCR was first designed (50's?), and is the proper tool for the job.

   If I did not work for the company I did (I have a few DC drives of my own), I would search EBAY for "DC SPEED CONTROL".  Most of the hits are good, but I would stay away from router controls, and the PWM stuff.  The simple, rugged, industrial DC drive is what you want.  Post your link here, and I'll be happy to check it out for you.

Hope this helps.

[Drives]

This is a good unit at a great price.  Don't know the seller, so be aware.

http://cgi.ebay.com/VARI-PAK-92A61633010000-DC-MOTOR-SPEED-CONTROL-NEW_W0QQitemZ280166055438QQihZ018
QQcategoryZ71393QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Any of the KB units should work well.  The brand Fincor, Reliance, Graham, Danfoss, Hampton, Morse, and (there are a bunch more) are all good units.  My link above is a totally enclosed unit with the speed pot, and on/off switch built in.

Hope that helps.

[Mary B]

full wave bridge into a capacitor filter is 1.4x the AC input