Hangzhou Delixi Group Co.,Ltd.

Frequency inverters have many advantages, this article will cover a couple of basic benefits which we use with most installations.

Speed Control
A fundamental principal of a frequency inverter is to adjust the speed of an electric motor. The basic command frequency for frequency inverters is normally from 0 Hz to 50 Hz, but with the average capability to be adjusted up-to 400 Hz. If the base frequency of a motor is 50 Hz then the final speed will be 8 times the base frequency of the motor with the command frequency set at 400 Hz.

Practically this is not normal for standard induction motors to operate at these high frequencies due to their design. In practice a command frequency set point of between 25 Hz and 75 Hz is acceptable without compromising performance or introducing any mechanical damage to the motor. At low frequency set points, care must be taken that there is enough cooling produced by the mechanical fan for the motor.

At High frequency set points mechanical failure may occur due to the mechanical design of the motor bearings normally rated at the design speeds of 2, 4, or 6 poles. At high frequency command speeds, care should be taken as torque loss may be experienced.

Torque Control
Basic torque control is possible in an open loop system; however, the actual system response required must be considered. In an open loop system the frequency inverter monitors the motor current and adjusts the voltage to perform torque control, depending on the installation, if the current of the motor does not vary sufficiently very inaccurate results will be obtained.

Position Control
With the aid of an optional interface card most frequency inverters have the ability to be used as a low cost position controller. Items to be taken into consideration are the dynamic response of the motor and control system. As a rule of thumb an open loop system with standard squirrel cage induction motor is approximately 400 radians /second, in a closed loop system with a standard squirrel cage induction motor and feedback approximately 600 radians /second. A full servo system is approximately 1000 radians / second. 1 radian / second = 9.55 rpm or 2π radians (rad.) in 360° or 1 radian = 57.3 °.

Smooth Controllable Starting and Stopping
A Simple adjustment of the time required to accelerate the motor from rest to full speed (Starting), normally 50 Hz and from full speed to rest (Stopping), ensures a smooth controllable start and stop sequence. This reduces mechanical wear on the machine. Various types of starting and stopping curves are available by setting the correct parameters in the frequency inverter as illustrated.

This article comes from inverter edit released