Using a Gearmotor with Variable Frequency Drive
A complete frequency inverter with a gearmotor has many advantages. A fully optimized system, especially when using an integral motor and a distributed VFD (sometimes referred to as decentralized control), is extremely compact. In addition, the efficiency can be significantly increased when the motor, reducer and VFD are selected together as a complete system, which effectively reduces the overall cost of ownership. A gearbox and motor operating with a VFD can operate over a much wider speed range, which allows for more operating flexibility.
Using a motor with a VFD will affect the operating temperature of the motor; even when the motor is running within its designed speed. The operating temperature becomes a concern when the motor is required to operate at very slow speeds as the mechanical fan can’t effectively cool the motor in this condition. When a low horse power motor is required, it is often most cost effective to slightly oversize the motor to compensate for the slow operating speed, and with larger horse power motors it may be more cost effective to utilize an auxiliary motor cooling fan. As mentioned above, the most cost effective solution can be selected when all components and aspects of the gearmotor and application are considered within the selection process. This ensures that the motor is not over sized when it’s not necessary, or that an expensive auxiliary motor cooling fan isn’t installed when a slight increase in motor size (which can be less expensive) may remedy an operating temperature concern.
Whether using a cabinet mount or distributed VFD; with a complete understanding of the motor, inverter and the operating requirements, it is possible to select a more optimized gearbox for the system than if just the required torque and speed are considered.