Contator coil failure
Contator coil failure
(OP)
What is the cause of the failure of a conatactor´s coil?
I suspect undervoltage. but, what is the mechanism of the fail?
Could it be that the contactor did not close so CEMF was missing and current on coil got too high?
Here is a picture of damaged coil. V=380 V - 50 Hz
I suspect undervoltage. but, what is the mechanism of the fail?
Could it be that the contactor did not close so CEMF was missing and current on coil got too high?
Here is a picture of damaged coil. V=380 V - 50 Hz





RE: Contator coil failure
A second common failure of AC coils is caused by mechanical vibration, wherein one or more turns short internally as insulation is mechanically damaged. The shorted turns act to greatly increase the current, again resulting in overheating.
A third failure, common to DC coils, is the failure of the economizer circuit to function, resulting in high current flowing in the coil for much longer than it is rated to accept.
old field guy
RE: Contator coil failure
RE: Contator coil failure
A more common cause of problems that end up looking like that is rapid opening/closing of the control command. For example a tank pump-up float switch acting directly on the coil without some sort of designed hysteresis in the system. Outflow from the tank will result in the float dropping, turning on the pump, it pumps, raises the float, which immediately stops the pump, but liquid is still flowing out, so the float drops, starts, stops, starts, stops ad nauseum, all taking place in a matter of seconds. Eventually the OL relay should trip because this is damaging the motor too, but often the contactor coil will fail first.
So if you have no other evidence of long term voltage sag, I would be looking at your control circuit very carefully. Sometimes even if it was designed correctly, a failure like this is secondary to another failure further up stream in the control system.
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington
RE: Contator coil failure
There is a tendancy to move to an AC activated coil but it has a DC converter circuit in it. The coil is actually DC and your contactor will stay energized down to about 50%. If you require details I will dig them up. Please let me know.
RE: Contator coil failure
Pressure switch is set for max and min. I dont know what are the values. I will check and see if conctactor is opening and closing repetitivly
Squeeky. I dont think that dirt is the problem in this case. Contactor was new and only worked for one week. The electric cabinet is hermetically seal (rain proof). I personally took it out and every thing was clean. By the way; What is VPCI?
regards,
lukin1977
RE: Contator coil failure
VPCI = Vapor Pressure Corrosion Inhibitors. They are little sponge like stick-on pads that you put in the enclosure which emit a vapor (gas) that coats exposed metal surfaces in such a way as to prevent oxidation and corrosion. Most enclosure mfrs sell them, or they can be found on-line. But be aware they cannot be shipped via air freight, so if ordering them on-line, don't pay the extra shipping costs because they will collect it from you, then ship it ground anyway because it is a hazmat.
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington
RE: Contator coil failure
RE: Contator coil failure
thsnks!
RE: Contator coil failure
from the picture it believes to me that this occurs due to the insulation failure between turns of the coil. As most area of the coil is burnt, but some area at the top of coil is still good, So it more seems inter turn short in the coil rather than any other reason.
Can you kindly share more pictures of coil so that we can understand more better?
THanks.
RE: Contator coil failure
Like I said before. The contactor is brand new
RE: Contator coil failure
RE: Contator coil failure
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington