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Thermal image inspection of equipment is becoming a regular part of routine maintenance.
As contactors are switching and carrying power, they can warm up a surprising amount compared to the surrounding ambient temperature. It is therefore necessary to understand the acceptable temperature rise limits.
Device temperature rise limits are detailed within the product standard IEC 60947-1, please refer to this standard for full details.
The temperature of the terminals can provide indication of a possible problem, such as a loose connection.
Table 2 clause 220.127.116.11 of IEC 60947-1 details the permissible temperature rise based on the type of metal used in the construction of the terminals.
For example, where the terminals are made of silver plated or nickel plated copper or brass, the maximum rise above ambient* is 70 K, resulting in a maximum termination temperature of 1100C.
*Note: Ambient temperature (temperature surrounding the device) limit of 400C is detailed within clause 6.1.1 of IEC 60947-1
The temperature of other parts of the Contactor, Overload, and Circuit Breaker may exceed the temperatures detailed above please refer to the standard IEC 60947-1 for details regarding these items.
Should the temperature rise be cause for concern, the following (not an exhaustive list) should be checked);
Check selection of the product against the catalogue for the given utilisation.
Check the duty cycle and operations per hour are within catalogue limits.
Check the cable capacity and condition of cables. Contactors rely on adequate cable sizing to assist with heat dissipation.
Check ambient temperature within the panel.
Ensure panel ventilation is adequate to ensure air circulation within the panel to avoid hot spots.
Check for terminal tightness in accordance with torque figures given in the product literature.
Ensure products are oriented correctly as per the product literature and recommended spacing clearances observed.
General observation and condition of equipment, any signs of scorching, burning or overheating should be investigated further.
This FAQ answer is provided for information purposes only. All maintenance should be carried out in accordance with a safe system of work by competent persons.
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