varible power supply for a pm dc motor

[spindown]

I need a schematic to make a variable power supply for a pm dc motor with 90 volt l5 amp rating. I want to vary the speed of the motor. Thanks Paul

[russlk]

This schematic will get you started. It was designed for 24 VDC and 50 amps but the IRF540 is rated for 100 volts (to be safe, I would use a 200 volt MOSFET). Change the 620 ohm resistor to 3.9K 5 watts.
http://www.geocities.com/russlk/motorckt.jpg
Copy and paste the URL because geocities does not allow links.

[Chris Foley]

Permanent magnet 90VDC motors are usually driven from DC motor drives, sometimes called SCR drives. These commercially available motor drives typically have speed control through a potentiometer which is either mounted on the enclosure or, for "open frame" drives, is connected at the terminal block. Most SCR drives have the capability of remote potentiometer control, and some have the capability of speed control through an analog input voltage (typically 0-5VDC or 0-10VDC). A few have the capability of isolated voltage control (electrical isolation from the line voltage), which allows them to be driven by a PC with a D/A output card or other control circuitry, without worrying about hazardous electrical potentials.<p>An off-the-shelf solution would probably be cheaper and more efficient than anything you could easily make yourself. SCR motor drives are just a more efficient way of driving 90VDC motors. The SCR control, which rectifies and then chops the AC line voltage, provides better motor torque at varying speeds. These drives also typically have IR comp, which improves the ability of the motor to maintain constant speed under varying load conditions. They are typically very easy to hook up and set up. All you have to do is read the manual that comes with the drive. If you're cash-challenged, DC motor drives can typically be found at industrial auctions. If not, there are numerous suppliers available.<p>If you want to do this yourself, you might want to look into SCR control of DC motors. There are a number of resources available on the subject, starting with the Gottlieb books on motors from Tab (I think). However, unless you <really> know what you're doing, this could be a very hazardous area for experimentation. 90VDC, whether floating or at line potential, is no joke. Happy hunting.

[Chris Foley]

<Quote> "...with 90 volt l5 amp rating..."<p>By the way, is this an 0.5A, 1.5A, or 15A motor? I think you've got a typo -- "L5"?

[spindown]

Thanks to respondents and the rating of the motor is 90 volts and 15 amps. Paul

[Joseph]

I am planning to do basically the same thing for an electric bicycle project. I am going to base it on the universal power supply circuit. Instead of using closed loop feedback as shown in the schematic, a potentiometer can be connected to the power supply output shown. Just run the output of the power supply through such a regulator as an LM317 before the potentiometer.
http://f3.grp.yahoofs.com/v1/kNkLPwqxoD ... Jomeis.GIF

[zotdoc]

There is an excellent article in home shop machinist magazine giving instructions on how to make a controller for a 90 volt5 dc Pm moptor up to 1 1/2 hp, using an SCR, diodes, a large amp bridge and a diac. I have a copy of the article and if you will send me a self addressed stamped envelope I will mail it to you.
William Miller
203 S. Shirley Ave.
Douglas, GA 31533