Inverter Vector Duty Motors
Variable speed drives are becoming increasingly common in industry, and with them comes the need for a new class of motors—those that are specifically designed for use with variable frequency drives (VFDs). These are called Inverter Duty Motors or Inverter Vector Duty Motors. They are available in many horsepower ratings and are suitable for most general-purpose applications.
The "inverter duty" specification means they can withstand the potentially damaging effects of the voltage spikes and other electrical anomalies that VFDs sometimes produce. The terms "vector duty" and "inverter vector duty" refer to the motor's ability to deliver optimal performance under precise speed and torque control, which is often needed in AC variable speed applications.
FAQs
Can totally enclosed fan cooled inverter duty motors provide constant torque at zero speed?
Yes, totally enclosed fan cooled inverter duty motors can provide constant torque at zero speed when used with a suitable variable frequency drive.
Are inverter duty ac motors appropriate for adjustable speed applications like material handling and machine tools?
Yes, inverter duty AC motors are appropriate for adjustable speed applications like material handling and machine tools due to their ability to operate efficiently at varying speeds with precise control.
Motor Starters, Soft Starters and VFDs
Motor Starters
Motor starters safely start and stop a motor in industrial applications. They are designed with a contactor, overload and circuit protection. They are used when basic motor control is required, where torque on the motor is not a concern and speed control is not needed. The advantages of motor starters include: lower cost, allows for remote operation, allows for monitoring of motor state (with the use of auxiliary contacts) and they are safe and efficient. The disadvantages include: high inrush current that can cause fuses to blow and breakers to trip if the inrush is too high, and the starter will allow a full torque to start the motor which can cause the motor to ramp up to full speed very quickly potentially causing the motor to wear and degrade prematurely.
Soft Starters
Soft starters protect motors from inrush current by gently ramping up the motor to full speed. They provide all of the same functions as a traditional motor starter. The advantages of soft starters include: they are less expensive than a VFD when only startup control is needed, they are a smaller system than a VFD where space is a concern and they prevent unwanted torque upon startup, prolonging the life of the motor. The disadvantages include: they are more expensive than a traditional motor starter and they do not allow for full speed control.
VFDs
A Variable Frequency Drive (VFD) allows for the slow ramp up of a motor during startup and the slowing down of the motor during shutdown. It also allows for full speed control during the entire run cycle of the motor. VFDs provide the same functions as both the traditional motor starters and soft starters. The advantages of VFDs include: full speed control (start, stop and in-between), more custom control and monitoring, energy savings due to efficient motor usage and less wear and tear on the motors. The disadvantages include: they are more expensive and larger than other motor control options and they generate heat that may require fans or AC units.