How to avoid coil damages?

[Murugesh_89]

Hi,
I am having a doubt in coil actuator/solenoid triggering. Normally we see this triggering using a transistor/fet or other switching device.

My doubt is if switching device is ON unknowingly ( may be device failure ) and at the same time the two ends of coil gets shorted. Then it will lead to overheat of coil and thereby it will burn and cause serious issues.

Some coils handle high ampere current in pulse format but can't sustain for continuous current of same ampere. In this case even if the coil not shorted and when the switching device ON unknowingly which will also lead to burning of coils.

Is there anyway to avoid these things?

Thanks....

 

[FvM]

People are using "smart" power switches, MOSFET drivers with built-in short circuit protection. It can't relieve you of checking maximum coil duty cycle when the continuous current is still within the driver's capabilities.

 

[chuckey]

"the two ends of coil gets shorted.", If the ends get shorted all the current will flow through the short and none through the coil. Some high power relays are fitted with an "economy" resistor, this is wired in series with the coil, but is normally shorted out by contacts. So the relay pulls in with a high current, the contacts open and the current drops to a level that can be maintained forever. If this truly worries you use a thermal fuse tied to the coil and wired in series with it. They are very low resistance but go open circuit at a preset temperature. They are used in lots of domestic equipment.
Frank

 

[smijesh]

Thermal cut off switch is the right solution. For my coil driver circuit I used thermal fuse as DF128S on the line and thermal cut off switch (KDS301) attached to coil (hot spot).

 

[schmitt trigger]

A PTC thermistor (like Raychem's polyswitch devices) in thermal contact with the coil may do the trick.

**broken link removed**