Conflict Between IEC 60034-25 and IEC 60079-14
IEC 60034-25
This standard addresses motors powered by variable frequency drives (VFDs). It allows for higher winding temperature rise because of converter effects, if the insulating system can sustain the stress.
IEC 60079-14
This standard is applicable to electrical installations in the hazardous environments. It strictly controls motor surface temperatures based on T-class ratings to prevent the ignition of combustible gasses or particles.
Conflict
A motor that meets IEC 60034-25 may yet exceed the safe surface temperature specified by IEC 60079-14, resulting in a contradiction between performance and safety criteria.
Resolution
The disagreement is resolved by derating the motor, adding cooling (or) filters and monitoring the temperature. In dangerous conditions, IEC 60079-14 always takes precedence because safety surpasses performance.
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