m) Temperature limit of coil

Temperature limit of coil

Q) To which class of insulating material are the solenoids coils of contactors have to subject?
What are their maximum permissible temperatures?

ANSWER:

The maximum permissible temperature of solenoid coils of contactors is 140 °C.
Example: Siemens make 3TF,3TH contactors coil sustain upto 140 degree C.

For these coils the maximum permissible temperature rise limit for coils in air according to class of insulating material is E = 100 K.
Since this is a temperature rise in Kelvin, this value shall be added with the maximum ambient air temperature of +40 °C of the contactors as described in IEC 60947-4-1.
The temperature rise limits applicable only if the ambient air temperature remains within the limits -5 °C to +40 °C.



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