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How do I bring this massive motor back to life? Answered

I have an old, fairly large treadmill motor lying around, and I would like to put it to good use again. However, I have a bit of a problem- the control board is missing, and I don't want to have to get a new one....
The motor has a sticker that says:
P.M. D.C. Motor Model-C3354B3304 (judging by the number of hits that I got on eBay, this model is probably fairly popular)
ICON P/N M- 190528
21.4 AMPS
CW Rotation
INS. Class H
1.5 HP CONT. DUTY @ 95 DC
ICON Health and Fitness.
(On the far right, it says "2.65 HP")
What would be the cheapest way to get this working? I was thinking of getting a bridge rectifier with http://search.digikey.com/us/en/products/GBJ2504-F/GBJ2504-FDI-ND/815157, adding an inductance to lower the current draw, and connecting some old caps from a computer SMPS to smooth the output, but I don't quite know if this will work. Can someone lend a hand?



Best Answer 6 years ago

First you probably do not need to use inductance to filter the motor
because the motors own inductance and mechanical inertia will
provide the smoothing you seek.

Another motor characteristic is that you should expect a ten per unit
starting current surge if starting is at full voltage.  Ergo your rectfier
needs to be rated at 200  Amps.  The transformer needs only to be
sized for the continuous load.  The thermal mass will not be affected
by an occasional 3sec 200 amp start that decays to load current ..


The bridge rectifier says that it has a max surge current of 350 amps, but only for 8.3 milliseconds (and I think the circuit breaker would give out long before that...).
Is there any way to lessen that startup load?

Start at reduced input voltage, easy to do with a contactor on a split winding
transformer or a series load that changes seconds after power on.

I decided to buy a 50 amp rectifier instead of the 25 amp one, and used the technique that you described to start it up (and it works, thanks!).

I still have a problem, though; even though I have a 20 ohm resistance (temporary, it doesn't work well) in series with the motor, it still spins up to dangerously high speeds (The mount I made looked like it was going to get torn apart, and the brushes began to arc!). Are there any reliable ways to reduce its speed?

(I've been thinking about taking Jack A Lopez's approach and using a dimmer switch, but it may not be able to handle the stress).

You are missing a major point.  All visible info on the motor is the;
  • Current = 21.4 Amperes
  • The HP = 2.65 horsepower × 746 W / HP = 1977 Watts
  • Supply VDC = W / I  = 1977 / 21.4 = 92.4 vdc
If you are running your system off of Rectified 120 VAC then ;
  • Rectified Peak DCV =  RMS × 1.414 = 120 × 1.414 = 170 VDCPEAK
  • That would add 80 Volt more then rated current causing motor damage
Keep in mind that running a 21 Amp motor off a 2 A light dimmer ain't going
to work.  If you do succeed and  make a high current phase control then
the high RMS current pulses will turn the solid carbon brushes to dirty dust
in less then 10 minutes.

So your  MAXIMUM DC MOTOR VOLTAGE  is only 90VDC   !!


Well, that explains a lot. Thanks for all the help, I think I can come up with something to deal with this (or not, but it's worth a try).

Alright, I'll try this. Thanks for the help!

Where would you find a motor mount & a DC rectifier for this? The mount would be used to mount it to a 1.5" or 2" round metal fence post. I plan to use a similar motor like this for a turbine project.


6 years ago

Hook it up to a gerbil wheel and give your rodent the thrill of its life!

I dunno.  Maybe a lamp-dimmer plus that beefy bridge rectifier. I'm not sure how much capacitor you want at the output, if any.  The motor might not care at all about large amounts of ripple.

I have not actually tried this, but my intuition tells me that it would work OK at low power, but maybe burn out the lamp dimmer if you turned it up too far.

Just a guess. You know.  That's waht the voices tell me.

Wot, no speed control ?