Contactor chatters when cold

[The Cobbler]

It appears the contactor in my lathe chatters when starting if it's cold .once it does that the first time, it's fine after that at first I thought it was gears because that's sort of what it sounded like, but I pulled off the covers & everything gear wise is totally fine looking. and with it only happening with the cold and over 4 years it's never got worse, I am pretty sure it's the contactor .
I guess my question is, is that likely and is there a fix for it? the lathe was originally 3 phase but it was converted to single phase by the store before I bought it.

 

[RPH]

If it’s been doing this since the beginning and only when cold. I wouldn’t worry too much. The laminated core is most likely a little loose when cold. Once running the eddy currents heat up the core to dimension. If it sounds like a train locomotive when engaged every time. Then the contactor is wore out physically.

 

[rlitman]

A couple of things come to mind. Contactors take more energy to close than they do to hold and that's where chatter starts.

It could be something with the laminations being a little off. The E core needs to seat with the moving part (could be a bar, could be another E, there are so many configurations...) for current to flow around the laminations, and if they don't make good contact initially, that can hamper the eddy current, allowing the moving part to bounce rather than clamp. Some surface rust on the mating contact surfaces of the E core (NOT the actual current contacts) can do the same.

What's the coil voltage? Is it an AC or DC contactor? Another possibility is something that drives the coil just doesn't have enough power output when cold. That's more likely with a DC powered coil, but not at all likely if the coil is line voltage.

 

[The Cobbler]

I suspect the coil voltage is 120 , and all AC . I can probably get a picture but it's buried deep inside .
I imagine this is the original contactor from the 70's

 

[The Cobbler]

 

[fitter30]

Most meters won' t catch the chattering. Try this Wires in series with coil wire.

https://www.supplyhouse.com/Supco-TD73-Time-Delay?utm_source=google_ad&utm_medium=Shopping&utm_campaign=Shopping_X_HVAC_X_SSC_ClassB/C&gad_source=1&gclid=EAIaIQobChMIqNmY8o2UigMV2jYIBR3cCzNEEAQYAyABEgJYYvD_BwE

 

[mm08822]

With power off, try to blow out the area. Remove the actuator assembly and see if there are any signs of scraping. Even surface rust could close down the clearances and cause the coil to pull in harder and not seal as quick as it should.

PICS?

 

[justsam]

Do you have the drawing for it after the conversion to single phase?

 

[micromind]

Some contactors will chatter when only 2 contacts are used and they are the center and one of the sides. When using only 2 contacts of a 3 pole contactor, use the 2 outside poles.

 

[mm08822]

Some contactors will chatter when only 2 contacts are used and they are the center and one of the sides. When using only 2 contacts of a 3 pole contactor, use the 2 outside poles.

I would hope all 3 remain even if single phase.

 

[micromind]

I would hope all 3 remain even if single phase.

All 3 are still there, the issue is that if you use only 2 of them and one is the center contact, they will wear unevenly and eventually bind the armature.

If you use the outside 2, the wear will be symmetrical and the armature won't bind.

 

[The Cobbler]

Do you have the drawing for it after the conversion to single phase?

No, that's just from the original manual

Some contactors will chatter when only 2 contacts are used and they are the center and one of the sides. When using only 2 contacts of a 3 pole contactor, use the 2 outside poles.

thanks, I will see if I can have a look at it. could I loop one of the contacts load side to line side and use that contact load side to motor?

 

[wyliesdiesels]

Yes you can. Done all the time

 

[larry_g]

I suspect that you have a drive that starts the spindle as soon as the contactor pulls in. If the drive is cold, thick lubricants, it will have a large current draw until things get moving. This large current draw can **** the voltage out of the system allowing the contactor to drop out. That kills the current draw and the voltage rises to pull in the contactor again. Repeat the cycle a few times and it is chatter till the spindle spins up a bit and the inrush current is lower allowing the contactor to latch in.

This is common on three phase machines that use the generated leg of a rotary phase converter. Has your machine been converted to a single phase motor? Is your electrical system from the breaker panel to the machine up to providing the inrush current? What HP is the motor rated at? What temp is a cold start? Is your shop unheated? All things that can play into your problem.

lg
no neat sig line

 

[The Cobbler]

I suspect that you have a drive that starts the spindle as soon as the contactor pulls in. If the drive is cold, thick lubricants, it will have a large current draw until things get moving. This large current draw can **** the voltage out of the system allowing the contactor to drop out

not sure what you mean, but this is a belt driven 240 volt motor, I can't recall the HP . if the motor is spinning, the chuck is spinning

 

[larry_g]

not sure what you mean, but this is a belt driven 240 volt motor, I can't recall the HP . if the motor is spinning, the chuck is spinning

Check the edits I made to my post while you were posting...

 

[The Cobbler]

Has your machine been converted to a single phase motor? Is your electrical system from the breaker panel to the machine up to providing the inrush current? What HP is the motor rated at? What temp is a cold start? Is your shop unheated? All things that can play into your problem.

yes to converted to single phase as per first post
yes to electrical, 30 amp breaker 10g wire
not sure on HP, forget... 1 to 1-1/2 if I recall
cold start temp 45/50° , shop is heated but set back when I'm not in there

 

[The Cobbler]

manual states it was available with either a 1 or 1-1/2 HP, 3 phase or single phase motor.

 

[larry_g]

1 yes to converted to single phase as per first post
2 yes to electrical, 30 amp breaker 10g wire
3 not sure on HP, forget... 1 to 1-1/2 if I recall
4 cold start temp 45/50° , shop is heated but set back when I'm not in there

1 One can convert a machine to single phase by installing a phase converter before the motor OR change the whole motor and controls, hence the question, Is the motor single phase.

2. A 1.5 hp motor can have up to 60a of inrush. So if you have a marginal feed or long length feeder then voltage drop can be a real issue.

4. That is a fairly cold shop. I would suggest that you you put the spindle in its slowest speed at the end of the day to give the drive the least load to get started in the morning. If you can disconnect the spindle from the drive all the better. On mine I can pull a pin to disconnect the spindle direct drive to put it in back gear. If you can do that and not engage the back gears then more load is removed. This may help identify if the start load is to much and may be a solution to your cold starts ups. This is also assuming that this is only a problem for the first start (s) of the day and when things warm up all is good.

lg
no neat sig line

 

[The Cobbler]

a single phase motor was installed prior to me buying it. re wired by the seller, sells tools & equipment
yes, it's just if I'm starting it cold , once it's gone thru some use it doesn't chatter. it never chatters in the summer or late spring/early fall when temps are higher .
I can put the headstock in neutral to start I suppose . never thought of that.
I'm going to look at the contactor when I have some time , maybe try to clean it up etc

 

[manwithtools]

All 3 are still there, the issue is that if you use only 2 of them and one is the center contact, they will wear unevenly and eventually bind the armature.

If you use the outside 2, the wear will be symmetrical and the armature won't bind.

Better practice is to route first conductor in series through contacts one and two and then route the second conductor through 3rd contacts.

 

[rlitman]

Better practice is to route first conductor in series through contacts one and two and then route the second conductor through 3rd contacts.

I guess, in the sense that more breaking points in the circuit divides the arcing more (across 6 gaps rather than 4). That would increase longevity, if you happen be using a 3-pole contactor on a single phase 240V load. But I have NO IDEA what micromind is getting at with regards to balancing the armature. The forces that the connected load current place on the armature are insignificant, regardless of how you wire it.

 

[manwithtools]

I guess, in the sense that more breaking points in the circuit divides the arcing more (across 6 gaps rather than 4). That would increase longevity, if you happen be using a 3-pole contactor on a single phase 240V load. But I have NO IDEA what micromind is getting at with regards to balancing the armature. The forces that the connected load current place on the armature are insignificant, regardless of how you wire it.

The main reason for doing this is actually old school. Back in the day when everyone used NEMA motor starters, they had thermal overload elements (heaters) that you selected based on motor FLA. If the load was not present on all three "heaters" they could trip the contactor due to phase imbalance detection. By routing the conductors as I described, you could equally load all three "heaters".

This behavior carried over into IEC starters with their adjustable overload units attached, so the practice of loading all three contacts evenly evolved.

In a DC application it's common to route the positive conductor thru all 3 contacts in series. In case of DC, it's done more so to provide a wider effective arc gap, (as you describe in your post) lessening the contact erosive effect of arcing. It's more important in DC as there is no zero voltage crossing event 60 times per second as there is in AC.

 

[mm08822]

I think he means as the contacts break, any "micro welding" between each respective pair takes some force (be it from springs or gravity acting on the armature) to drop out the armature. Using L1 & L3 is symmetrical about the centerline(L2) of the armature.

Otherwise it could skew as it drops out.

 

[Norcal]

Is the armature mating surfaces of the contactor rusty?

 

[The Cobbler]

Is the armature mating surfaces of the contactor rusty?

not sure . will dig have to dig in to it and see .

 

[TheEquineFencer]

I'm going to inject a past experience with a contactor in an Automatic Transfer Switch that was doing something similar. It "worked fine" but had a "hum" when energized. I found the contactor had some metal shavings from where the contractor installed it keeping the mating surfaces of the pull in from sitting perfectly flat. Basically, it had an "inductance hum." There was a fine metal shaving that looked like it'd been hit with a hammer imbedded in the surface. I removed it, polished the surface and the hum went away. Just a thought.

 

[RPH]

Remember it only does when cold. Once warmed up it goes away. I lean to loose laminations in the actuator, once warmed by the eddy currents they tighten up enough no more chatter. Most of the things discussed so far the noise would be constant while in use. Only when cold is the key statement.

 

[rlitman]

Remember it only does when cold. Once warmed up it goes away. I lean to loose laminations in the actuator, once warmed by the eddy currents they tighten up enough no more chatter. Most of the things discussed so far the noise would be constant while in use. Only when cold is the key statement.

I guess my question then is how you want to define chatter? A buzzing noise could certainly be caused by loose laminations, but when I read contactor chatter, I'm thinking of chattering CONTACTS, and that's far less likely to be caused by loose laminations, because a pulled in contactor should maintain good contact even with some armature buzzing (that's why there's a separate set of springs over the contacts).

 

[PoorUB]

I can put the headstock in neutral to start I suppose . never thought of that.

That might be all you need!

I suspect, like the other post that the cold machine has a crazy start up load and large voltage drop because of the load on cold start up.

Put the spindle in neutral and see what happens, although there might be a large portion of the gear box still spinning in neutral. But start it in neutral and see if it starts fine. If you does you might just run the machine in neutral for a 15-20 minutes to get some heat into it, then try it in gear.

 

[The Cobbler]

I tried running it in neutral for a bit and no chatter

 

[The Cobbler]

I lean to loose laminations in the actuator,

so do you recommend replacing the contactor?

 

[RPH]

Not at this time. I would agree to a tear down type inspection. As I said previously that when a contactor wears out mechanically it will be a progressive increase in the noise, it won’t stop once engaged. Inspecting and a cleaning can’t hurt. Most contactors are meant to be rebuilt.
It’s the noise disappearing that I think matters here when warm.

 

[The Cobbler]

I also did look at the contactor and it has 3 terminals , with one jumped so all terminals have load on them

 

[Jim greengo]

Can you swap it out for a 2p contactor with a 120v coil?

 

[The Cobbler]

^^^ probable could, I see no reason why not. ( other than I'm cheap) LOL

 

[RPH]

If you replace it. You still need to remove it. So, I would start with removal and inspection. That’s the cheapest way to go at this point.

 

[The Cobbler]

added to my TDL list . inspect contactor on lathe .
not much experience wit them. are they obvious how they come apart? all I know is it's Allen Bradley

 

[rlitman]

... are they obvious how they come apart? all I know is it's Allen Bradley

Just lots of springs and a few small parts (the shading rings) that fall out at the wrong moment. Simpler than a typical lockset. If you've got the part number, diagrams should be easy to find, and it's not the sort of thing that fits back together multiple ways.

 

[The Cobbler]

found this thread while searching , too bad it has all the water marks on the pictures