Question

The thermal loading on the motor can be determined by:
1. Duty/Load cycle
2. Temperature of the winding
3. Age of the motor
4. Ambient conditions

Answer 1

Correct Answer - Option 1 : Duty/Load cycle

Thermal loading:

• If the generation of heat equal to dissipation of heat, electrical machines will be the stable temperature at this condition but if machines work under over load so high current will pass so that heat generation will be over than dissipation heat and machines go to unstable at this time electrical installation in machines defected by temp rise.
• Motor overload condition mainly results from abnormal use of the motor, harmonics or unbalanced supply voltages.
• They all increase the motor losses and cause additional heating.
• As the temperature exceeds the rated limits specified for the insulation, the winding insulation deterioration accelerates.
• This will shorten the expected lifetime of the motor and may lead in some point to an electrical fault in the winding.
• The thermal loading on the motor is determined by the duty/load cycle.