Single phase 1/8HP motor wiring 2

[DynahoeDave]

IHi everyone,
I recently acquired a 1960's Bridgeport milling machine. The cross feed has a motor driven feed mechanism.
The motor Nameplate:
Master
Alternating Current Motor
Serial DV6265 Style 245574
Type PA Frame 5217 H/P 1/8
Volts 208-220 Cycles 60 / 50
Amps .7 Phase 1
RPM 1725 / 1425
Code M Temp. Rise Cont 50 C

It has 2 Black #16 AWG wires. Also, 2 blue #18 wires, and a red #18 wire. One of the blue is connected to a 71-90 MFD 110-125V capacitor. Metal can, rubber terminal end with 2 lugs. The other lug is connected to the red wire.

It also has a KB Electronics solid state motor switch [model KB-6] . One line connection goes to the yellow [line] wire of the KB-6. The other line connection goes to one of the black motor wires. The loose blue wire goes to the KB-6 red / start wire. The remaining black wire goes to the KB-6 Blue main wndg wire.

I have this connected to 240VAC line. It is drawing around 4 amps, which is really high for such a small motor, and way over the .7 on the nameplate. I have a clamp on ammeter, and it shows 4amps in the run winding, and a pulse during start in the start winding, and in the capacitor wiring.

I removed one end cover, and the windings do not look discolored, burned, etc. The bearings are good, and all of this is with no load on the motor.

I did a few tests trying to determine if a winding is bad, or somehow they had been swapped or miss wired, as the wiring in the machine was kind of a hack job in places.

I left the black wire connected to one line input. I disconnected the Motor switch. Wired a 100W incandescent in series with each of the 2 windings, and connected the other side of the lamps to neutral, to give it only 120V. Both lights light up nearly full brightness, motor does not turn or buzz. If I momentarily bypass the lamp on the start winding, it spins up, and the other lamp dims, as I would expect. Actually, the start lamp dims also, but not as much. And it will continue to run with the start circuit open. If I then bypass the lamp in the run winding circuit, the motor continues to run, hum gets a little louder, current goes up to about an amp. Obviously, if I were to go to 240, the current would go up to the 4 amps I measured at the start of realizing something isn't right. It almost seems like it would be happy to run on 120VAC - although I don't know if the torque would be there. But with it wired to the KB-6, it doesn't do anything with only 120V applied.

Alll of my wiring description is based on how it was when I got it, so there could be an error in the assumptions. I'm hoping to find someone familiar enough with this sort of motor to confirm / help narrow down anything I'm missing.

[the main [3 phase] motor on the milling machine I got a VFD for, and it's working great]

 

[Skogsgurra]

Bill just added a point worth considering. I mostly see three phase windings with a run capacitor. Then it works. But if the number of turns in the start winding differs - it will not.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[flexoprinting]

Bill

I didn't see your other post till now and that is a possibility I didn't think of

However, with a number of common arrangements, if the run winding is interchanged with the start winding the current and the heating will be much higher.

LPS for that method of testing, will wait for OP to reply

Thank you Gunnar!

Chuck

 

[DynahoeDave]

The windings are not electrically separate, one of the main wires is common. One of my early thoughts was that possibly the start & run windings were swapped, but yesterday's investigations showed they were not.

The capacitor has 2 wires that go into the windings. When I connected a lamp in series with each winding feed, the start winding drew more power [it's lamp was brighter] once I spun the motor up.

I determined the start winding wire was actually the start winding - since the current going into it always matched the current through the capacitor.

The start winding wire is 18AWG, and the run winding wire is 16AWg, as is the common one. The 2 wire to the cap are also 18AWG, Does this wire gauge difference make sense or give a clue?

Unless the cap is wired completely incorrectly.... It will not be easy to trace as the wires go into the windings lacing, and it's all coated with enamel / varnish.

The capacitor is soldered to it's 2 wires, unlike the other connections which are wire nuts. This caused me to not think of the capacitor being miss wired as easily as any of the others...

There is no indication anywhere the the motor needs to be reversed electrically. The table feed direction is selected by a mechanical lever and gearing / dogs.

 

[flexoprinting]

Well since you checked and ruled out those possibilities my call would be to say you have failed winding's, without a meggar test @ 500v it's difficult to know for sure. Separating/running stator leads out for testing is difficult. Depending on mounting of motor to gear box acquiring the same motor would be easiest unfortunately it's looking like your options are a motor repair shop, fleabay and a roll of the dice, or re manufacturing the mounting system with a new motor and similar specs .

Chuck

 

[itsmoked]

Powerfeed??

Keith Cress
kcress -

http://www.flaminsystems.com