Contactor Chattering

Assuming that you have positively ascertained that there is no control wiring problems or excessive voltage drop when going to high speed, that your motor connections are correct and the motor windings are good, you should check that the associated pole faces are coming together cleanly and that the shading rings are in place and unbroken.

Check that the mechanism moves freely and that there is no gunk in the spring/slide sections as this can cause both slow uptake and slow release.

One possibility is an unidentified foreign object located somewhere in the mechanism. If so then it needs dismantling to remove, as it is probably paramagnetic and lodged somewhere; a blast of air is unlikely to remove it.

Try another contactor...from a different batch...check contactor coil for proper voltage, check amperage draw when engaged...

Mathew45167,

Can you fill in some blanks for me please?

Has this contactor been used to supply voltage to these motors previously?

Is this a new motor control setup?

Is the contactor new or used?

How old is the contactor?

It must be several years old as the part number you spec is an older part number and has been replaced by # LC1D32G7

What voltage are you running through the contactor to the motors?

As per the part # the coil should be 120 VAC.

Has the coil voltage been verified on the coil data sticker?

Have you checked the 120 VAC at the contactor coil?

If yes, what voltage was read?

If no, Then you need to check the 120 VAC at the coil when it is chattering!

Please supply the answers to the above questions and we will do our best to assist you.

Thank you

Bryan

As far as I think it's the coil voltage.. energizing and denergizing all depends on the coil voltage.. but still I read it working fine when the other speed is in operation..

It needs a considerable voltage fall to "drop-out" - 20% on top of 20% . 0.8 nominal supply volts at motor itself is usual minimum - usually coil gets much more. See data below.

Pull-in & drop out depend on springs & magnetic gaps - which can be increased by corrosion or foriegn bodies holding moving part away from intended stop. They depend on coil temperature - when cold, as when first test done, resistance is 30% less than hot coil. Problem with hold-in circuit and many other causes have been posted as possible.

Neither supply, control nor motor voltage have been given. No reply has come from original question poster to eliminate any cause. The test I suggested, do "start" test without motor current, was intended to check if control works at normal voltage.

It should be obvious by now that the OP likely already solved this problem as we keep spinning our wheels. While it would be nice to know if our suggestions helped to solve this puzzle, we will just as likely not get any feedback. I suspect the root of the problem was actually something embarrasingly simple or stupid and not one of our more exotic scenarios. This fits the mantra of "horses instead of zebras" and the deafening silence.

sorry for the late reply was busy in exams

1.- contactors are new, but i use the same contactor for slow and fast forward and another contactor for slow and fast reverse movement.

2. its not a new control circuit.

3. 380v supply to the contactor with 110v ac coil voltage... transformer ready the same no problem in 110v ac

"... whats the reason behind this. ..."

Any one or more of the following (many already mentioned):

• Foreign object, rust or deformation in the pole faces of the contactor armature
• Broken shading coil in the armature
• Welding contacts
• Improper mechanical and/or electrical interlocking
• Bad coil
• Voltage drop caused by the added current draw on change to High Speed operation
• Under sized conductors (tied to the above issue)
• Too small of a control power source (assuming control power transformer or power supply)

I remember seeing this scenario happening due to condensation on the contacts. The quick vaporization to steam would open the contacts briefly. A sealed contacts contactor was the solution. This was a very unusual failure scenario that was difficult to repeat just in case you have overlooked all of the other scenarios.

More often I found the vibration of the contactor engaging was making a loose connection to the coil into a bounce creating switch.

"the contactor instantly starts chattering".....

1/ Could you help us by identifying the contactor? - you have a forward contactor, a reverse contactor and probably two contactors to change speed.

If contactors are same type you could try substituting reverse contactor for chattering one, see if runs OK forward.

It has been suggested chattering contactor may have poor connection.

I suggest you isolate the the 460V?? supply and energise the 120V?? and check that each contactor works OK when its coil is linked direct to 120V. They should all operate with same speed and "clunk".

2/ But you have not told us what contactor coil supply is - please write.

Those contactors could work on DC supply if they had a ballast resistor switched-in, once closed. DC supply can avoid the humming of AC contactors.

If the ballast resistor burns-out, then the contactor will "cut its own throat" as soon as it energises and chatter. The coil might overheat and fail quite soon if it chatters. Usually, the contactor switches the ballast resistor with its own "late break" contact - but it could be a separate relay/timer.

The start sequence ends with the final contactor latching-itself-in electrically via stop button/emergency stop - you might have a fault with those contacts - but please advise on result of above checks before going to more complication.

?

I think the voltage drop..

i did as u suggested isolated the motor and operated the contactors.. it works fine... please if you could share me the circuit diagram

110v ac coil voltage

Since the contactor works fine without the load of this 3Φ motor, it sounds like the starting current in reverse is sagging the power line and thus the control voltage enough for the relay to drop out. Now why is this different from forward motion, I cannot tell from my laptop. You need to look at the voltages with a voltmeter. It would be nice to also get current values with a clamp on meter.

Could it be that the reverse command is being given even before the motor comes to standstill??

If true, the motor would draw starting current much more than the rated magnitude and that could be causing excessive voltage drop.

Contactors work - at least at normal 110V.

Putting two contactor coils in series and measuring voltage of each coil may help - you may have to push contactor mechanism closed - it is just a crude way of seeing if suspect contactors hold-in at about half volts [specification for release 0.3 to 0.6 x rated] without having a variable supply or resistor to test. Various wattages of 230V lamps, series or parallel connected, might give a selection of resistances in series with coil.

Next step is to press "start" with motor isolated [ two motor fuses out, only phase & neutral to control transfo kept or control supply only energised]. If correct contactors operate and hold-in, at least control circuit is functional.

This might be the connection diagram for your motor, however constant torque rating for 8/2 pole would be say 4/16 kW.

This would mean connection of speed contactors was quite simple. It is probable there are timers/interlocks to stop instant forward/reverse/forward; HI/LO/HI speed - as pointed out by other post, this can cause exceptional currents/wear on motor/ coupling/ contactors/load.

A check of control voltage or motor current during actual start attempt would help. Normal voltmeters will not show fast dips - filament lamp may be more revealing. To me 70% rated volts still looks white, but 50%/60% is yellow/bright yellow. A neon lamp may go out at half volts - they have a definite strike voltage - you could calibrate one with two potentiometers and voltmeter to only light at known peak voltage.

This may help.

https://www.electricaltechnology.org/2014/06/Two-Speeds-Two-Directions-3-phase-Motor-Power-Control-Diagrams.html

Obviously both overload relay contacts must be in series at position marked "overload relay". This is not shown, which does not inspire confidence. You do not have a K4 contactor. I would expect a K3 N/C contact to be in K5 coil circuit, similar K5 contact N/C in K3 coil circuit.

There is nothing obvious to chatter - except supply volt dip on motor start current. If the K5 hold-in contact did not operate, motor would run if you held start button down.

Some schemes have mechanical link between K1 & K2 and between K3 and K5 which is a special twin assembly - obviously K1[K3] & K2 [K5] on together is a flash|bang event.

1. Have you tried taking control supply transformer input direct from another circuit independent of motor start current?
2. Have you checked control supply is actually 110V ?
3. What happens if you select direction and then connect high speed contactor coil "hot" direct to 110V with wire link?
4. Have you got two overload relays or any relays additional to essential 4 contactors?

As far as I remember LC1 family overload relays latch-out mechanically once tripped & have a mechanical reset button on top, but some overloads do not latch and operate an electric latching relay.

Another possibility is that the release spring has failed, lodging part of it in the mechanism.

"All electrical problems are actually mechanical ones." _{- Anonymous Poster #0}

shading rings!

Take a thermal camera and look for an upstream current restriction. Sounds like the inrush on the two pole motor is pulling down line voltage enough to drop out the contactor and turning it into a door buzzer. Alternately, try operating the contactor from a separate control circuit so that the contactor solenoid voltage is independent of the motor line voltage.