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  #1  
Old Tue 26 February 2008, 21:40
ekdenton
Just call me: Ed #8
 
Alamogordo, NM
United States of America
Power supply transformer - series/parallel of the output (secondary) side

I am using the the oriental 2A motors and have been calculating my power supply. I think that I have it figured out okay but hope to get a check on my calculations.

I will wire the motors half coil or unipolar. Wiring them unipolor rather than bipolar will increase the amp draw of the motors from 2amps to 3amps.
The square root of the inductance of these motors is 1.23
So 1.23 x 31.6 = 38.88VDC Which should be the DCV i will need to supply the motors.

I have the 300VA 25+25 toroidal 6A.
I will rectify one of the 25VAC secondarys.
25 x 1.4 =35VDC


The toroidal didn't come with any data but I take it that the 6A rating is for secondary series wiring, and hence the reason for not using the series wiring if using the 2A motors? Using the lower voltage should give higher Amp rating of the transformer, and still run the motors properly?

Output voltages I calculated are aproximate since I have no way of knowing if the rating of the transfomer is loaded or unloaded rating, plus the AC line voltage here can vary 5 or 6 volts
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  #2  
Old Tue 26 February 2008, 23:11
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
ED, the 6 amp rating on the transformer is the amount of current allowed to flow in the output wire. When those output coils are in series, it is effectively one long wire making 50 volts carrying 6 amps (50 X 6 = 300).

When you put the transformer output coils in parallel, you have 2 wires side by side each carrying 6 Amps, total 12 Amps, making 25 Volts (25 X 12 = 300)

If you only use one coil of the transformer, you only get 25 X 6 = 150VA

No harm in having excess VA's available on the transformer side - parallel the output coils to get a full 300VA at 25V AC, which rectifies to 35VDC.
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  #3  
Old Wed 27 February 2008, 09:01
ekdenton
Just call me: Ed #8
 
Alamogordo, NM
United States of America
Thanks Gerald, I understand now.
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