Capacitance

[Enzo]

On split secondary transformers, if it is rated 40 amps at 12vAC, that is with the two secondaries in parallel - 20 amps each. But in series for 24vAC the two 20 amp windings in series do not add, So you get 24v at only 20 amps.<p>I really doubt filtration is the issue. 24v at 40 amps is almost 1000 watts. That is a very large transformer, 1000 watts. I would expect it to be the size of a bowling ball almost.<p>You say the AC primary does not sag under load, but how about the secondary? It starts at 12 per winding, but what does it sink to under load? If it goes down to 6v, all the caps in the world won't help. You would need larger tranny.
In model railroading we used to have a switch that removed the filter from the 12vDC for slow speed operation. The pulsing DC made the moter more effective at low speeds. Your motor might actually prefer raw pulsing DC. Or maybe not.

[bsparky]

Voltage does sag to 7vdc under load. What do you think of connecting to of these trans. and bridge rect. in parallel on the DC side. I wish I had a DC amp. meter so I could confirm the DC amperage, I have a AC meter. Anyway to use an Ocilliscope?

[jwax]

BTW bsparky, what sort of terminals are you using to connect the supply to the motor? I'm hoping they're heavy duty clean copper lugs and bolts.
Anything like jumper cables will cause your excessive voltage drop.
That 5 volt drop (12-7) @ 40 amps is a 200 watt heater burning somewhere!
John

[dyarker]

Sounds like you still have the transformer secondaries wired in series for 24VAC. They need to be in parallel for 12VAC at 40Amps.

[bsparky]

Thats just it there is no heat anywhere, all leads are soldered except at the bridge rect. stackon connecters. Have not been up to the club in awhile, but will have to check trans. wire like you suggest Dale, but I'm sure I wired it according to wiring dia. on the trans. I believe that was parallel, will check. Any ideas about measuring DC amp. really don't want to buy DC amp meter. Not much call for one these days with AC motors and drives. No use for it at work any more. Thanks