Page top

V/f control


The appropriate product category
  • icon_right_b.gifInverters
A control method that enables preventing reductions in the power factor or efficiency of a motor in a wide range of variable speed operation for changes in the frequency for speed control by outputting a voltage (V/f characteristic) corresponding to the frequency set by a parameter in an Inverter. The revolution speed of an induction motor is proportional to the frequency, which can reduce the power factor and efficiency of a motor even with a variable frequency because changes to the frequency cause the internal impedance of a motor to change. Therefore you must change the voltage corresponding to the frequency. V/f control reduces the torque in low-speed operation with the primary resistance voltage drop even through it attempts to keep the torque stable regardless of the frequency. A torque boost can increase the torque somewhat in low-speed operation, but it never produces optimized control, causing the current-torque ratio to drop and resulting in an inability to get the same torque as the base frequency. It also requies the troublesome boost adjustment.