Contactor Humming as Soon as Voltage Increases

I've never seen nor heard of a contactor coil with that wide of a range for control voltage....are you sure you're reading it right..?. what is the type and model number and brand name of this contactor?

Its for agri market.. 2 pole contactor coil.. declared is 154 to 264V.. brand is BCH

I don't see any contactors with a range stated for control voltage....

https://issuu.com/bchindia/docs/bch

Contactor coil if supplied by bridge rectifier (connected permanently at its terminals) can remain pickedup even up to 45% of rated coil voltage.

This is considered a plus when it comes to motor starters used for Agriculture pump sets.

It doesn't mean the contactor can pickup when the voltage is low (at the bottom end of the indicated coil voltage range).

Thus, it is normal if the contactor is only humming and not picking up when the voltage is low.

As well, when the voltage goes very low, i.e. close to bottom of the range, with contactor in picked up state there is a possibility of contactor humming (and hence drawing higher current).

Is the contactor and coil are reputed make? Is it ISI marked? To my experience there are many small panel manufacturers who use substandard contactors and coils for their panels which results in these types of problems. (Not the reputed company like L&T Snider, Crompton, and similar) The problem with substandard product is the core assembly is not with proper plates and assembly is not tight which results in core heating core humming, coil burning. Even for good quality contactors overheating and prolonged use and repeated operation cause humming due to rust on core face and improper alinement. I have even come across Agro motor control and starter manufacturers who ask you in advance weather we want reputed contactors and coils or ordinary ones for different prices. So better checkup for the quality. BCH is a reputed manufactureer . So you have to check whether it is manufacturing defect .contact the company.

"BCH Electric Limited, an ISO 9001:2008 Company, is one of today™s leading Switchgear manufacturers & LV Panels Manufacturers of low voltage electrical and electronic controls in India. The Company was established in 1965 as a joint venture between Cutler-Hammer, USA, and Indian partners. Since 1977, it is a wholly owned Indian Company with global business connections."

However L & T gives coil of 180-410V. SO range Is not an issue.

Perhaps it doesn't know the words?

????

It is a humorous response to the joke: "Why is (fill-in-the-blank-here) humming?"

This is a reference to someone trying to sing along with a song, but since they don't know the words, they hum the tune instead.

These motor starter contactors have coil voltage parameters of operation stated in %'s...Including coil rated voltage, coil operating limits, and electrical consumption among others, but they also have a proper coil voltage stated.........The noise(hummm) is no doubt harmonic resonance...

https://cdn.automationdirect.com/static/catalog/17-motor-controls-contactor-starter-relay-disconnect.pdf

Actualy the problem is the behaviour of contactor.. as soon as we increase the voltage the noise should be reduced.. but here the case is different.. initialy it is silent and become noisy as we increase the voltage..Just need hints what can be the possible reason...

New electronic coils have a small on-board auto-ranging switch mode power supply to a DC wound coil. So you can feed it a wide range of AC input voltages and it just steps it down with a small transformer, rectifies it to DC, then uses a DC PWM chopper to operate the coil at its design voltage.

In that little SMPS, there is a transformer and most likely the hum is the beginnings of that transformer starting to fail. You are hearing magnetostriction acting upon the core laminations, but that core should be solidly riveted to prevent that. So if you can hear it, the core laminations are getting loose. Failure is eminent.

Ah yes something new....well, new to me...that explains it, if in fact it is one of these coils...

https://news.thomasnet.com/fullstory/contactors-incorporate-electronic-coil-control-design-19826

One of the possibilities is that there is an unintentional foreign object lodged in the mechanism that requires removal.

The humming is caused by mechanical movement of the wire windings or associated iron magnetic cores. As the voltage is increased, the current increases. The magnetic force increases and movement/deflection of wires and cores also increases. At some point it deflects enough to make an audible hum or the movement reaches the point that two surfaces in the assembly make contact, causing a noise. This may or may not be a problem, depending on whether the deflection, contact and noise indicate a wear surface or a stress concentration that will eventually lead to wear failure or fatigue failure of some component of the assembly. It's probably normal that a component run at higher power will fail before a component run at lower power, but if it is within the rating and of reasonable quality, it should provide reasonable service.

The fact that your contactor STATES that the coil voltage has a wide input voltage range can ONLY mean it has one of these electronic coils. There is no other way to make a coil that can accept that wide of a range. So the noise that the coil makes as the coil voltage increases indicates a failing coil.

The other issues of foreign objects etc. do lead to contactor noise, but would NOT be tied to a change in the coil voltage.