Boom, help finding replacement contactor

After a year and half without my beloved 10EE due to living temporarily somewhere else then a shop move, I was thrilled when power was finally dropped today. It ran beautifully for several minutes until ... smoke, lots of smoke, then a muffled boom and everything died.

Upon investigation with my electrician it's believed the 3 phase leg which ran the 120V electromagnet for the contactor had the bad luck to get the stinger so it got 209V instead. At least those are the words he used and I believed him. The electromagnet is rather a nasty shade of melted now. I'm hoping the VFD itself is fine.

My lathe has what I believe to be an Al Sharon VFD conversion. I'm seeking help to find a replacement contactor of the same make/model as there are lots of wires coming off of it and if possible I'd rather do a straight swap. I couldn't find any writing on it but I am including photos and I hope someone will recognize. You can see the scorch marks on the backside view. Any leads appreciated.

The photos appear to be upside down in this post, though not upside down on my phone or computer. curious. Happy to send directly to anyone if that's helpful.

wfrancis said:

After a year and half without my beloved 10EE due to living temporarily somewhere else then a shop move, I was thrilled when power was finally dropped today. It ran beautifully for several minutes until ... smoke, lots of smoke, then a muffled boom and everything died.

Upon investigation with my electrician it's believed the 3 phase leg which ran the 120V electromagnet for the contactor had the bad luck to get the stinger so it got 209V instead. At least those are the words he used and I believed him. The electromagnet is rather a nasty shade of melted now. I'm hoping the VFD itself is fine.

My lathe has what I believe to be an Al Sharon VFD conversion. I'm seeking help to find a replacement contactor of the same make/model as there are lots of wires coming off of it and if possible I'd rather do a straight swap. I couldn't find any writing on it but I am including photos and I hope someone will recognize. You can see the scorch marks on the backside view. Any leads appreciated.

The photos appear to be upside down in this post, though not upside down on my phone or computer. curious. Happy to send directly to anyone if that's helpful.

View attachment 174464View attachment 174465View attachment 174466

Click to expand...

"Al Sharon"? I'd call it "Al Qaida". Definitely not like anything Monarch ever shipped...



Replacing like with like is not the best idea when the critter has exhibited catastrophic failure of that sort rather than tripping-out the VFD, a fuse or breaker. Control power deserves appropriate protective devices, just as operating power does.

If the VFD is not toast, it is entitled to be.

I doubt I'll be the Lone Ranger in suggesting best way forward is to give us a good shot of the motor nameplate. And-then-also.. tell us what you have available for power outta the wall.

Expect to be advised to remove all the rest and do it over, better, with a new VFD, fuse or circuit breakers, rated on-machine disconnect, all sized and wired per the VFD maker's specs -

IOW - Schematic is in the manual. Needs nought but a note or three. No more mystery, anywhere, hence easily maintainable / standard-component replaceable, going forward into the far future.

And.... that any competent VFD actually has no pressing need of an external, third-party magnetic starter, anyway.

Which is the only half-way sane rationale for a contactor of that type even being present at all. "HALF way".

And their wiring is dirt-simple and widely published even so:

"ON" from a normally-open momentary switch, usually a pushbutton, carries coil power to the actuator.

Hold-in aux contact parallels that whilst power is available, drops-out and STAYS out until re-energized manually should power fail.

"OFF" from a normally-closed momentary switch, usually a pushbutton, optionally alone or with one or more Normally-Closed E-Stop switches in series, ANY of which manually interrupts hold-in coil power.

Check your VFD manual.

It may have a relay that presents a 'dry' contact closure to operate an external contactor to the same functionality IF it is also provided with control power separately from the power it is meant to be making 3-Phase variable frequency out of.

A single-phase 120 VAC or 240 VAC direct input, for example: Fused, AND NOT switched, before it hits the VFD.

If so, and it had been set for 120 VAC - with no fuse - that's why I suspect the VFD has been toasted by the same 200+ VAC that cooked the contactor's coil. Control circuit likely to be damaged. Control relay coil and/or contacts overloaded to failure.

A simple, dumb VFD with no such options MAY have survived.

Check the Enable/Run control optioning, you can probably confirm that by simply bypassing the toasted contactor. Fuses strongly recommended.


Bill

Bill,

I think the problem was the control voltage to the contactor was on the high leg of 240 delta three phase. That looks like a generic 4 pole contactor with a aux contact block.

I doubt the VFD is damaged.

Steve

Steve in SoCal said:

Bill,

I think the problem was the control voltage to the contactor was on the high leg of 240 delta three phase. That looks like a generic 4 pole contactor with a aux contact block.

I doubt the VFD is damaged.

Steve

Click to expand...

No question as to why it was damaged (the contactor).

Some question as to why it was THERE and neither fused nor already documented. Generic or 'as built' schematic. Make & model/ Part Number - ELSE generic specs. And yes, it should be vanilla / generic, anything with comparable ratings a near-as-dammit drop-in, and wiring 'obvious'.

That said, I'm sure it is not 'news' to anyone, but VFD's inherently perform their own 'Starter' functionality by simply optioning to NOT re-start after a power interruption until told to 'Run', or at least 'Enable' manually.

"Remotable" those inputs are as well. So, too E-Stops and RPM controls.

If one wants to preserve legacy on-machine control switches, all of the above can still work w/o need of a contactor OR direct access to the VFD's control panel.

Bill

A master contactor is rather common, perhaps not on a single motor VFD install but, with a coolant pump it makes sense.

All my machines with more than a single motor and, other electric devices have main power contactors. The ones I have reworked have all been brought up to 24 VAC control power. The VFD would provide low voltage control for it however, a coolant pump had line voltage control when installed back in the day. Most machine re builders today will convert to low voltage control so the machine conforms to NEC and OSHA rules. That the contactor was not fused is a concern, that it is 120 VAC not 24 is odd as well but, the application of a master is not unusual.

Steve

If it helps, I can put you in touch with another owner of a 10EE with an Al Sharon conversion that is working fine.

The contactor is nothing special. Just a generic definite purpose magnetic contactor. Usually used in cost concern applications like HVAC Look them up in the grainger catalog.
If I were you I would use a better grade of contactor. Like a Square-D NEMA contactor.
All you need to know is the coil voltage, the current rating, the number of poles and any pilot duty contacts.

Now the real question is why was the control not properly fused to prevent the damage that occurred?
From what I see in your photos I would be surprised if it is fused at all. The quality of the wiring is hideous. Good luck on your repair hopefully the drive was not damaged.

Ron

Thank you everyone for your thoughts. This is all very new to me so I appreciate your input and advice. I've run this lathe in two other locations with no issues so I had no idea there was a potential problem lurking with missing fuses or other not-well-thought-out configuration.

I've looked at what seems like hundreds of contactors on Grainger and google and have yet to find one that looks even remotely like mine so I think a direct swap is unlikely. I do appreciate the comments that another replacement should be fairly easy to source. Mine has wires coming off it in many places which go to the power button, power button light and power off button (at least), but on the other ones I've seen online I don't notice the auxiliary terminals to connect such things. I'll do more research and then source more wisdom here before buying. I'll be at the shop later this week and will make a schematic of the current layout and report back.

I'm including a photo of the fried coil for your amusement (and perhaps sympathy)

@rimcanyon - I'm not sure I need to see another Al Sharon VFD conversion, however, I might serve as a warning to your friend who may have a similar setup. Later I'll post pictures of my complete setup you an pass along and perhaps another problem can be avoided.

Thanks again, Will

Do you know the current rating of the blown contactor?

Steve

Steve in SoCal said:

Do you know the current rating of the blown contactor?

Click to expand...

I don't, as it's not labeled and I haven't found anything like it, but it is getting 3ph 240v and always been on a 30 amp breaker. The motor is 5hp and I'll get a picture of the plate in a couple days.

I'm happy to report my lathe is fixed and running beautifully!

My shop neighbor happened by and it turns out not only did he have a contactor which would work but also he's done this exact repair several times. He's friends with the guy who runs the local scrap yard and over the years several machines have come in with fried contactors. Usually it's because someone has swapped voltage on the motor but forgot to do the contactor but supposedly has seen exactly my problem as well. I guess this issue is the last straw for some or a machine just gets left in the corner and eventually scrapped. I'm told the owner of the scrapyard has a surprisingly nice machine shop of "junk" machines.

I had made a schematic the day before so it only took him 10 minutes to hook it up. The VFD is fine but for some reason I can get "only" 3800 RPM out of it where it used to crank to 4000 no problem. Not sure if it's a this-power-location thing or ... ? I don't care though and am very happy!

Once I made the schematic it was actually much simpler than I thought. I really do appreciate so many willing to jump in and give advice.

Will

wfrancis said:

Mine has wires coming off it in many places which go to the power button, power button light and power off button (at least), but on the other ones I've seen online I don't notice the auxiliary terminals to connect such things.

Click to expand...

Will,

As you (now) know, all he did was use the AUX contact terminals as if they were what SHOULD HAVE BEEN a separate terminal-strip for all the low(er) voltage goods. One fuse could have protected the entire lot of 'em - contactor coil included.

Fortunately, those were mostly make-break switches and no other load was compromised besides the contactor's coil .. or so we hope and trust..



As to the VFD.. if not damaged it could still have been subject to a spike that altered one or more of its settings. If you HAD 4,000 RPM, getting the other 200 back may need only a reset to defaults and touch-up of only the few parameters as need any settings change at all.

Bill

I would suspect that the machine lacks an isolation transformer for the control voltages. The contactor was probably run on the 120 volt leg of the 220 input using the machine ground conductor for the neutral. When it was hooked up it got tied to the wild leg,or red leg and that put 190 volts on the 120 volt coil. It may have put the wrong voltages on some other part too.

John