Why should Overload Relay settings be adjusted for High-Inertia Motors?
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High-inertia motors take a longer time to accelerate because of they drive heavy rotating loads such as
- Crushers,
- Fans,
- Centrifuges,
- Conveyors and
- Large pumps.
During starting the motor draws high current for an extended period.
If the overload relay setting is too low (or) the trip class is not suitable:
- The relay may trip during normal motor starting.
- Frequent nuisance tripping may occur.
- Motor startup becomes so unreliable.
- Production interruptions & equipment stress may increase.
Therefore overload relay settings should be adjusted properly to allow the motor enough starting time while it still protecting it against overheating & overload conditions.
Important Adjustments
Select the correct overload current setting based on the motor full-load current (FLC).
Use a higher trip class (such as Class 20 / Class 30) for a long acceleration times.
Consider the motor starting characteristics & load inertia.
Ensure a proper thermal protection without any unnecessary trips.
Common Applications of High-Inertia Motors
- Conveyor systems,
- Ball mills,
- Large blowers and fans,
- Crushers,
- Centrifugal machines and
- Heavy industrial pumps.