Last week in Part II, we discussed several electrical line-side issues which should be factored in when selecting a drive. Life would be too easy if this were the whole story. There are several critical load-side (i.e. from the drive output to the motor) concerns which should be examined carefully because they can impact equipment life and your prime mover’s ability to perform the work necessary for the process.
Load Side Considerations:
- Motor amperage: Drives are properly sized by amperage, not horsepower. In order to ensure proper output capacity, the driven motor nameplate full load amperage (FLA) should be known. It is important to note that sizing the drive based on FLA is not merely being conservative. Under the working assumption that the motor is sized correctly for the load torque needed, sizing a drive for only what the motor draws under “normal” (i.e. non-peak) load conditions may not provide sufficient torque to drive the process under heavy load conditions. Also, sizing a drive by horsepower alone ignores the amount of overload the drive can provide. For example, a 460-volt drive suited for a 75hp motor under variable torque conditions may be […]