Help - Lathe motor running backwards - no oil pressure

ChriS2000 · Dec 15, 2019

Hey guys, hoping for an assist here.

My electrician and I got a 220v single phase circuit ran for my lathe yesterday, hooked up the static phase converter, fired up the lathe, and it's not making any oil pressure. Lathe runs on 230v 3 phase.

After some detective work, I'm almost sure that the lathe motor is running in reverse, which is in turn spinning the oil pump in reverse.

Last night I tried switching two of the leads going into the disconnect box on the machine (middle leg stayed the same) but then the motor wouldn't start at all.

There are absolutely no markings on the motor, and the wires for it are quite inaccessible as it's huge and stuffed into the machine base.

This type of electrical work is a bit out of my area of expertise, but I can follow instructions if anyone has any suggestions. Thanks for taking a look either way.

Phase converter:

Disconnect box on the lathe:

Starter box on the lathe:

JohnEvans · Dec 15, 2019

Does the lathe have a F-R switch ? If so try that in the other direction. How many HP is the lathe motor and does it have a clutch so the motor starts unloaded ? Try switching the center and one of the other wires. About the biggest HP non clutched lathe motor I have successful ran on a static box was 2 HP,above that went to rotary converter system. You can use your static box with a correct [as big as box is rated for] idler motor to make a rotary setup.
EDIT is the oil pump driven from the lathe motor or septerate motor? If septerate switch any 2 wire at that motor.

ChriS2000 · Dec 15, 2019

JohnEvans said:
Does the lathe have a F-R switch ? If so try that in the other direction. How many HP is the lathe motor and does it have a clutch so the motor starts unloaded ? Try switching the center and one of the other wires. About the biggest HP non clutched lathe motor I have successful ran on a static box was 2 HP,above that went to rotary converter system. You can use your static box with a correct [as big as box is rated for] idler motor to make a rotary setup.
EDIT is the oil pump driven from the lathe motor or septerate motor? If septerate switch any 2 wire at that motor.

No electrical reverse switch, lathe does that with gearing.

Lathe motor is 7.5hp, the lathe shifter has a neutral position so it can be started out of gear.

The static converter is rated up to 10hp, doesnt seem to struggle starting or running the machine. The oil pump is belt driven off of the main drive belts coming off of the motor.

I'll try switching leg "B" with "A" or "C". Does it matter where the legs are switched, as in top vs bottom of the disconnect, or top of the starter box?

johnoder · Dec 15, 2019

Maybe the feed for the mag starter coil circuit is being lost in the process

If those electrolytic caps drop out after starting the motor you only have two hots going to lathe at that time

I.E., statics are not three phase makers outside their starting lash up

13engines · Dec 15, 2019

I would say put the two wires back like you had them before. Then go to the box where the contactors are and determine which two wires are the ones that feed the coils of the contactors. Then either in that box or any box before that, reverse those two wires from whatever connection they're on.

In short hand... you want to make sure the two wires you electrician brought in are the same two wires that feed the coils of your contatcors. Your contactors probably say 220v somewhere on their coils.

Dave

ChriS2000 · Dec 15, 2019

13engines said:
I would say put the two wires back like you had them before. Then go to the box where the contactors are and determine which two wires are the ones that feed the coils of the contactors. Then either in that box or any box before that, reverse those two wires from whatever connection they're on.

In short hand... you want to make sure the two wires you electrician brought in are the same two wires that feed the coils of your contatcors. Your contactors probably say 220v somewhere on their coils.

Dave

Dave, can you explain in simpler terms which contactors / coils you're referring to? I'm guessing they're inside the starter box.

13engines · Dec 15, 2019

ChriS2000 said:
Dave, can you explain in simpler terms which contactors / coils you're referring to? I'm guessing they're inside the starter box.

Yes, the box in the last picture with the Square D stuff in it. They coil connections might say A1 and A2. The L1 L2 L3 or T1 T2 T3 connections are your power connections.

I would suggest that you do not change the connections at the coils but before the wires get there. Changing the connections at the coils won't do anything to change rotation direction.

Rob F. · Dec 15, 2019

Use that static converter to power another motor, you then have a RPC, giving you much better 3 phase power.

ChriS2000 · Dec 15, 2019

13engines said:
Yes, the box in the last picture with the Square D stuff in it. They coil connections might say A1 and A2. The L1 L2 L3 or T1 T2 T3 connections are your power connections.

I would suggest that you do not change the connections at the coils but before the wires get there. Changing the connections at the coils won't do anything to change rotation direction.

Ok cool, that was the consensus that my electrician and I had too. I'll report back in a bit after I try it. Thanks for the advice.

ChriS2000 · Dec 15, 2019

johnoder said:
Maybe the feed for the mag starter coil circuit is being lost in the process

If those electrolytic caps drop out after starting the motor you only have two hots going to lathe at that time

I.E., statics are not three phase makers outside their starting lash up

The starter cap in the converter definitely drops out after thr motor is running, but I can't imagine that would affect the direction of rotation right?

ChriS2000 · Dec 15, 2019

I swapped the "A" and "B" legs going into the power disconnect box on the lathe and it worked! Previously I had tried swapping "A" and "C".

Also my theory about the oil pump was correct, and now it's got a solid 40psi of oil pressure.

Thanks for the help everyone!

13engines · Dec 15, 2019

ChriS2000 said:
I Also my theory about the oil pump was correct, and now it's got a solid 40psi of oil pressure.

Glad to hear that you got things turned round.

This is something you can take with you into the future should you buy another machine or when getting into CNC machines. The first motors you want to run after wiring in a new machine are not the main drives and spindles, but the coolant pumps or hydraulic pumps and the like. Even coolant pumps without coolant can be jogged on for a couple seconds just to check rotation. Many CNC controls will run the spindle in the proper direction no matter which way the machine is wired. So first paying attention to the smaller 3 phase motors is the safest bet. If one small motor is running the right way, likely all the other things are too. Still they all should be checked at some point.

Dave

ChriS2000 · Dec 16, 2019

13engines said:
Glad to hear that you got things turned round.

This is something you can take with you into the future should you buy another machine or when getting into CNC machines. The first motors you want to run after wiring in a new machine are not the main drives and spindles, but the coolant pumps or hydraulic pumps and the like. Even coolant pumps without coolant can be jogged on for a couple seconds just to check rotation. Many CNC controls will run the spindle in the proper direction no matter which way the machine is wired. So first paying attention to the smaller 3 phase motors is the safest bet. If one small motor is running the right way, likely all the other things are too. Still they all should be checked at some point.

Dave

Thanks Dave. The oil and coolant pumps on this particular machine are mechanically driven off of the spindle drive belt, which is turned by the main electric motor.

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Help - Lathe motor running backwards - no oil pressure

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