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tonguesandwich
10-05-2006, 10:48 PM
What can I use for a power source for a 90 vdc motor -Dayton (4z728A)? Wouldn't mind slowing it down (89 RPM)

slash
01-03-2007, 08:38 AM
A transformer. Would it blow on 110v AC? If not, you don't need a transformer, just put it on a surge protector.

Scottzilla
03-16-2007, 01:54 AM
Since it's a DC motor you would need to use some diodes or a bridge rectifier after your transformer to make sure it always receives the correct polarity, otherwise it would probably just sit there and shake back and forth.

slash
04-04-2007, 06:54 PM
Since it's a DC motor you would need to use some diodes or a bridge rectifier after your transformer to make sure it always receives the correct polarity, otherwise it would probably just sit there and shake back and forth.

What the hell is a bridge rectifier, LOL I don't think the polarity would get reversed from the simple turning of a motor, it doesn't change the wires around. AC is alternating current, DC is direct current. AKA AC is constantly changing direction. Maybe you mixed up the two?

Scottzilla
04-09-2007, 06:11 PM
We're both right about AC vs DC; I think you're thinking of the problem backwards though.

AC = Alternating Current = "constantly changing direction" = reverses polarity 120 times a second.

DC = Direct Current = doesn't change polarity

The motor wants DC (same polarity the whole time). If you reverse the polarity on a DC motor it will run backwards.

If you run AC through a transformer you get a different voltage out the other side but it's still AC (DC won't go through a transformer at all).

Since the motor wants to see a constant polarity and instead it sees the polarity switch back and forth 120 times a second with AC it probably won't run.

A bridge rectifier basically converts AC to DC. It has four diodes inside that make sure that whatever polarity you put on the two input terminals, the output terminals always have the correct polarity. The output voltage will still rise and fall like AC, but the polarity will never change (True DC has a constant voltage & doesn't rise & fall like an AC wave). This should be good enough to run a DC motor (I've had pretty good luck with this method).

slash
04-12-2007, 04:31 PM
I got ya. However, I've seen transformers convert 12AC to 120AC, but I've seen DC ones too, maybe they had these bridge rectifiers in them?

Nightmaretony
04-12-2007, 04:37 PM
yuppers, they use a bridge rectifier. Also, if you try connecting a DC motor to AC power, all it will do is burn, hum and smoke...

Scottzilla
04-12-2007, 04:43 PM
Hey, that could be a pretty scary effect, even if it's not quite what you're looking for... :D

imax
04-13-2007, 08:22 AM
Unfortunately, I've never seen inexpensive 90vdc power supplies. You can probably build it cheaper than you can buy it, the ones I see immediately are variable 0-100vdc, and are the rock-starts of power supplies, clocking in around a thousand bucks.

If you can run off batteries, you can string them together in series to get 90 volts. If there's sufficient current, it will hurt (and likely kill you), too!

My suggestion: Return the motor for an AC version or a lower voltage DC version. If you go with DC, 12vdc is best, there's lots of inexpensive ways to power them.

Or, if you have the talent, go build a power supply for it.

-- I

Scottzilla
04-14-2007, 02:42 AM
I use a Variac for weird voltages like that:

http://cgi.ebay.com/3-Amp-Variac-Variable-Transformer-NEW-8275_W0QQitemZ320102675542QQihZ011QQcategoryZ73153 QQrdZ1QQcmdZViewItem
(not my auction; just an example)

$49 is better than thousands of $s, but still not very cheap. I guess it helps that I already have one.

If you really want to get your motor going you could pick up a Variac, plug it in, adjust it so that it is putting out 90v AC, hook up a bridge rectifier to convert it to pulsed-DC, then connect your motor. Of course, for the money you're spending you could probably get a different motor like imax said.