Noisey MEM switch

Even the slightest piece of dirt will stop the poles of an open frame contactor from mating properly, with resultant buzzing. Take it apart again and wipe the faces, clean them again and then wipe with a no residue solvent like acetone. Don't apply lubricant, the faces should be bone dry.

In terms of the magnetic circuit even a few thou gap is very significant.

Andrew

If the starer is not fixed to a flat surface the case can be distorted and prevent complete closing of the poles.

Emgee

You may have some copper inserts in the poles, check they are not broken.

Mike

It could also be the operating coil beginning to weaken, depending on age of course.

Edited By Brian Sweeting on 08/11/2018 14:15:25

I like Andrew's suggestion as being more likely, but loose laminations are a possibility. Worth a look at how they are held together in your switch.

Dave

To me it sounds like the laminations are vibrating because of the alternating magnetic field. Maybe a copious coating of varnish or paint would "glue" them together again, and solve the problem.

Howard

The pole faces should dry and free from even the smallest particles to avoid that annoying bussing sound. All the starters and contactors I've seen have had ground pole faces. I remember taking some noisy one apart and having the faces ground a second time hoping to improve things, but that was when labour was cheap.Years ago MEN and other motor starter manufactures offered a resistor and rectifier kit so that to coil was operating on DC, that eliminate the buzz completely. John

check the screws that hold the contact box to the armature are tight, they cause noise! look also at the screws/tabs that hold the lower armature to the base, and generally (with the power off of course!!) tighten everything up. Hope this helps.

Phil.

Is the starter mounted on the machine? check that the contacts for the overloads are clean, and also the little holding in contacts on the top, next to the three main ones. If the machine has even a very small amount of vibration, this can cause the overload contact to arc, and cause buzzing and random noise. Better off mounting them on the wall and using a remote stop/start on the machine. If you look at the bar which bears on the end of the overload heaters and push the bar against the spring you open the overload contacts, and can inspect them.

Reading one of your posts you say you changed the switch from you drill and that one made the same noise when you fitted it to the lathe, so is there another electrical fault that is causing the problem loose contact elsewhere in the system start from the plug and work through the electrics buying a new switch may just be spending money that need not be spent.

I hope I did not read that post wrong

Yes, the lower clip os usually the culprit, but we must allow for the fact that it is old, and it has been, as you say, on the lathe for 60 years! they do get noisy, and there are things you can do to quiten them, but after a time it becomes a hiding to nothing. The problem is, what do you replace it with? British and European are fairly expensive, and the alternatives are either Indian or Chinese. Last new one I fitted came from a local electrical wholesaler, was indian, and cost about £45-00. It was ok, fitted to a v twin 2 stage 3 phase compressor, bit small internally, but generally ok. Looked it up on Alibaba, to find that they cost $4-50 per unit if you buy 100! The MEM starters are well made, and just about bullet proof, but can be noisy....................................

Good luck with it!

Phil

Just read the last post again, if you have a VFD, it mat be interacting with the coil to cause the noise, something to do with the squarish waveform vfd's produce, why not take the starter off and start the motor from the vfd, and also fit a remote stop to the VFD so you have an emergency stop?