Hi all.

I got a "Naniwa" (chinese?) single phase series AC motor. I tried to reverse the rotor connections (brushes) as I figured out this is the way it is done in hand drill.

It is rated 220v/0.5 amps. I connect 2+5, 6+4, and connect 1,3 to 220v AC. Runs fine, 18,000rpm as stated.

The problem is, it runs fine in normal, but to reverse, I connect 2+6, 5+4, and 1,3 is 220v. It runs about 11,000 rpm, brushesh spark out , and gets warm soon.

My fear is , this is uni directional motor. Is there any way to change winding? I guess need to get my head around winding the motor...just don't have time. So previous experience is much appreciated..



There are 2 symmetrical stator windings, and one rotor with brushes.

 

I must admit that this is odd. The two wires that are connected to the brushes should be capable of being swapped.

 

Probably brush allignment; for bi-directional rotation, brushes are in-line with commutator diameter.

 

Probably brush allignment; for bi-directional rotation, brushes are in-line with commutator diameter.

I dismissed that thought but there doesn't seem to be any other obvious explanation. What was it that S. Holmes used to say....?

 

good morning.

I was carefully monitoring the contact are of brushes , as soon as saw this problem. I'll try to file the brushes, so either direction the contact area is the same.
But...will this help? another question is, I don't have any cap hooked up into motor, should I put one? which contacts?

Thanks

 

Universal (Brush) Motors don't require Start Caps. They have very high stall torque. If you do find caps, they're usually very small disk caps, used to reduce RFI only.

 

I've managed to hook up stators to 12 v DC, and the rotor to ~45v DC. Runs ok, can reverse by reversing rotor connections. But, power is sacrificed obviously..


the next step, is to connect all in series, and hook up to DC, see how it runs..

 

I've managed to hook up stators to 12 v DC, and the rotor to ~45v DC. Runs ok, can reverse by reversing rotor connections. But, power is sacrificed obviously..

If it's a series motor I would expect the the stator and Armature windings to divide up the supply voltage as per the manufacturer's design . Why have you been applying 12V to the Stators and 45V to the Armature? This may be partially the source of your excessive sparking but not certain.

the next step, is to connect all in series, and hook up to DC, see how it runs..

Why haven't you been running it like this to start with?

 

I was testing at which current the stator windings start becoming warm, hooked up paralel to 12v DC, about 2.7A (a bit high for winded wire gauge), and in series connection almost draws 1.3A.

one thing I found out, is stator windings are ~3.6 Ohm each, and the rotor (single contact place) is ~28 Ohm some. So in series, much power will be dissipated by greater resistance, so staror should be ok.

the answer is, I was planning to have fixed connections on stator, and then remotely change rotor connections, to reverse with built relays with radio control.

I just thought about connecting stator and rotor in series to same supply source rather that separate. will try today.

 

Well you could have tested reversing the armature leads with everything in series to start with. These motors are popular for their high stall torque and variable speed using PWM. The schematic that Sgt. Wookie drew for the Split Phase Motor thread can be adapted to your motor.

 

Probably brush allignment; for bi-directional rotation, brushes are in-line with commutator diameter.

Exactly.

The motor brushes are usually offset to counter armature reaction if a motor is designed to run in a single direction, which is what happens in the OP's case.

Running the motor in reverse would require adjusting the position of the brushes to reduce heavy sparking caused by commutation. This can't be done if the brush housing is fixed to the motor frame and does not allow adjustment.

 

When motors are designed as such it's fairly obvious when looking at the brush holders as they mate with the commutator. I would have thought that the OP would have noticed it.

 

Thanks gents, valuable suggestions. I'll get back with findings once get a chance to sit behind my desk this weekend..

 

I dismissed that thought but there doesn't seem to be any other obvious explanation. What was it that S. Holmes used to say....?

"After eliminating the impossible, whatever is left no matter how improbable must be the answer."
AND
"Elementary...Watson."

 

"After eliminating the impossible, whatever is left no matter how improbable must be the answer."
AND
"Elementary...Watson."

Yeah, that it!

 

good day.

this damn motor is a lump of confusion...so..

I connected only rotor to DC 50v, runs! (no stator connected yet)..I reverse the polarity, it runs in SAME direction..weird..

I connect the stator to DC 12v, I can reverse by changing rotor, but speed is less than when it runs without stator hooked up...

I've connected the stator and rotor in series with ALL possible permutations of wire connection, no result at all trying to reverse..

I'm guessing best thing to do , is find another motor...

 

Good morning all.

The solution was an easy one, just needed a small experiment...

I hooked up motor to variable AC power supply, I can reverse now by only reversing ROTOR connections, as would be normal from the first day.

The problem starts after ~ 150v. Runs normal, by sparks out in reverse. at ~ 180v sparks become bigger.

So, I run it now from 110v AC power supply, and no problem reversing.

Just for easy hook up, I'll use 110W light bulb in series, and hook the motor directly to 220v. The motor is 110W, so in theory the voltage should be devided in half between the motor and the bulb. We'll see.

The devil is in the detail...

 

Good morning all.


Just for easy hook up, I'll use 110W light bulb in series, and hook the motor directly to 220v. The motor is 110W, so in theory the voltage should be devided in half between the motor and the bulb. We'll see.

The devil is in the detail...

I see you have discovered the value of the tungsten current limiter

 

)) easy physics, equal powers split the voltage) and the easiest match for 110W was the bulb..

I'll post some photos after I get finished with the door, hope everything will work as per plan..

 

The downfall of your power splitting plan is that it will only work up to a 110W load (0.147 HP) on the motor. That is the balance point at which the voltage will divide equally. Above that, the voltage split will cause the voltage on the bulb to increase above its voltage rating and it will then become a fuse if that increase is significant.