Lathe humming when trying to start.

B

Black Jack

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Ottawa
Thought of asking here since most guys in here have a metal lathe. I have a Jet 1550 with a 3 phase motor. I'm using a phase static converter using 240v single phase. Everything always ran fine. I've been gone for 3 months and wanted to thread a barrel last night. Motor humms but will not start. It's not really the motor but the contactors in the electrical panel of the lathe. It kinda jerks a little to want to start but it stays there. I can spin it by hand easily. If I manually press the contactors for forward or the reverse one. It does the same. Humms but won't turn. I suspect humidity got somewhere and prevents full power to go where it needs but where to test? Anybody has an idea where to go from here. Tks

Pat
 
Not sure but sounds like the capacitor might be shot. Look for a cylindrical shaped silver or black “tube” somewhere near the motor, 2 wires. Sort of stores power so the motor can get spinning, also sometimes attached to contacts inside the motor that switch it out when the rpm gets high enough, kinda looks like a little governor but disconnects a couple of contacts so the motor runs off straight ac when it’s wound up... might be bad contacts not allowing enough current for start up.
 
Well to start messing with three phase motor starters is not something you want to be doing as a non electrician. From what you describe I would check there is voltage at the motor as it sounds like you have lost a phase but where, it could be at your phase converter, overloads on the motor starter the fuse or breaker or even the motor, broken windings would not affect the mechanics so the motor would turn by hand.
Also there are no need for capacitors on a three phase system capacitors and starting windings are only needed on a single phase motor.
 
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One phase is not getting power, that's why your getting the humming and a little jerk of the motor when you turn it on. Check your wiring, I see it all the time where one wire of the plug will pull out inside the plug. If there's nothing wrong and your getting the correct voltage to your motor it's your motor that's shot.
 
Blackjack it sounds like one of the relays is stuck there should be three in the control panel of the lathe you can manually engage it by pushing on the tabs on each side of it and should free it up they get sticky sometime.
 
Single phase hum of a 240V motor is caused by a missing phase. Likely one of your fuses is "blown" or a conductor (wire path) has opened. Trust me, I'm an electrician.

Scott
 
first is the lathe getting any power, humming is typical if one phase (wire) is not connected, check the lathe plug has all wire connections good, also at the converter, a cap could be the issue but you have several and doubt they all failed.

there is also relays that can corrode, if they are the open type get some contact cleaner and spray on contacts, check all connections, you should also see if there is voltage across all 3 wires
 
Do you have a volt meter? Are you comfortable using it?

Trouble shooting procedure;
1. Check for voltage at the receptacle, should be 240v between phases, 120v to neutral for each phase. If yes proceed with steps, if no check fuse/ breaker in panel.
2. Are there fuses in the lathe control box? If so check for voltage out of each.
3. Check if any relays are operating properly.
4. Check if there is a start capacitor and if there is voltage present in and out.
Let us know how you make out
 
not gonna lie, i had this happen to me once on a ski tuning machine - everything ran fine no problems, but after having the shop kid clean the work room, the machine would boot, touch screen control panel would come on, the motor would hum but wouldn't fire up the next day.

after calling the manufacturer and having the tech come out (from another province) and check everything, play with the panel and breakers we figured it out.



The plug had partly come out of the wall. We figured the shop kid hit it with the mop the week before
 
Update, checked for power in my phase converter, all good both lines coming in at 115v. Checked output all good going out 3 legs 115v. Checked in the electrical panel of the lathe. all good there also. Checked fuse. Oooooh... one is not good. Hopefully that's it. Now I need to find an FLNR 30. Checked online but nothing close. Anybody knows what type of store would carry such a beast? Tks
 
Black Jack said:
Update, checked for power in my phase converter, all good both lines coming in at 115v. Checked output all good going out 3 legs 115v. Checked in the electrical panel of the lathe. all good there also. Checked fuse. Oooooh... one is not good. Hopefully that's it. Now I need to find an FLNR 30. Checked online but nothing close. Anybody knows what type of store would carry such a beast? Tks
Click to expand...

Nedco - 700 Industrial Avenue, in Ottawa.
 
Black Jack said:
Thought of asking here since most guys in here have a metal lathe. I have a Jet 1550 with a 3 phase motor. I'm using a phase static converter using 240v single phase. Everything always ran fine. I've been gone for 3 months and wanted to thread a barrel last night. Motor humms but will not start. It's not really the motor but the contactors in the electrical panel of the lathe. It kinda jerks a little to want to start but it stays there. I can spin it by hand easily. If I manually press the contactors for forward or the reverse one. It does the same. Humms but won't turn. I suspect humidity got somewhere and prevents full power to go where it needs but where to test? Anybody has an idea where to go from here. Tks

Pat
Click to expand...

It doesn't know the words?
 
Black Jack said:
Update, checked for power in my phase converter, all good both lines coming in at 115v. Checked output all good going out 3 legs 115v. Checked in the electrical panel of the lathe. all good there also. Checked fuse. Oooooh... one is not good. Hopefully that's it. Now I need to find an FLNR 30. Checked online but nothing close. Anybody knows what type of store would carry such a beast? Tks
Click to expand...

Buy one of these https://www.tecowestinghouse.com/products/Drives/fm50.html and run your 3 phase lathe off a standard 115 single phase outlet. I finally got around to installing mine and it works perfectly.
 
I have one on my milling dirtybarry. I love it. Will probably go this route if the fuse doesn't fix my problem. Thanks JZA for the location. I'm not too far from them. Will go there. Tks
 
When checking voltages check phase to phase, not phase to ground on a 3phase three wire system. 115volts to ground is not a good way to see if you static phase converter is ok. Phase A-b, b-c and c-a. They should all read 240 ish volts
 
Black Jack said:
Update, checked for power in my phase converter, all good both lines coming in at 115v. Checked output all good going out 3 legs 115v. Checked in the electrical panel of the lathe. all good there also. Checked fuse. Oooooh... one is not good. Hopefully that's it. Now I need to find an FLNR 30. Checked online but nothing close. Anybody knows what type of store would carry such a beast? Tks
Click to expand...

Me, I'd stick a piece of copper wire in place of the blown fuse, and try the motor.

If it grunts, groans, or otherwise makes odd noises, I would very quickly kill the power and start shopping for a new motor. Otherwise I would take it on faith that the motor was good and the fuse finally gave up, and replace all the fuses, as they are, no doubt, of a similar vintage.

YMMV.

In this day and age, there are enough choices for Variable Frequency Drives out there that I would not be too enamored of a static converter.
 
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