What are variable torque loads?

VARIABLE TORQUE LOADS: Many types of loads require reduced torque when driven at speeds less than the base speed of the load. Conversely, such loads may require increased torque when driven at speeds greater than the base speed of the load. These are classified as variable torque loads.

Can VFD control torque?

Torque control mode allows for the VFD to directly control motor torque instead of motor speed. This is necessary for any application where torque takes priority over speed.

What is VFD torque compensation?

Also known as the torque compensation, it’s to compensate the torque decrease in low speed for the stator winding resistance of the AC motor, by increase the low-frequency range of V/F.

Which motor gives best variable frequency speed control?

AC motor. The AC electric motor used in a VFD system is usually a three-phase induction motor. Some types of single-phase motors or synchronous motors can be advantageous in some situations, but generally three-phase induction motors are preferred as the most economical.

What is the difference between constant torque and variable speed?

As the speed changes, the load torque remains constant and the horsepower changes linearly with speed. Constant torque loads cause motors to draw relatively high current at low speeds when compared to variable torque applications.

How do I select a VSD?

Sizing a VSD?

  1. Remember the motor is a source of torque.
  2. Remember, motor speed is not limited by network frequency.
  3. Correct motor selection based on load type.
  4. Know the operating speed.
  5. Forced ventilation.
  6. Ensure the duty cycle is correct.

Which mode provides the best torque and speed control?

As compared to the V/Hz mode, the SV mode delivers higher starting torque, tighter speed control under varying loads, the ability for low speed operation down to 1% for maximum rated speed and the possibility of generating up to 200% of rated torque for a brief time.

How do you increase the starting torque of a VFD?

To deliver the high starting torque, the v/f ratio of VFD output is deliberately made more than 8 for a definite time to generate more flux in the airgap. More flux will lead to more torque than the motor-rated torque. V/f Pattern in the case of starting torque boosting is as given below.

How does a VFD control motor torque?

Vector control accomplishes this by using current feedback from the motor. Current feedback is measured via current transformers inside of the VFD. Constant current readings and rapid calculations performed in the VFD determine present torque demand and flux.

What is the difference between ECM and PSC motors?

The big difference between the two models is that the PSC motor has one speed: full speed. Any time that the blower is on it blows at full force. The ECM model is a variable speed unit that will adjust the airflow to optimal levels based on the desired temperature of the home.