Direct torque control

Emotron VFX variable speed drives

Emotron launched the first variable speed drive in 1982 and direct torque control was introduced in 1998

 

By measuring the motor current and voltage it is possible to continously, and with exact precision, control the motor's torque and speed in real-time. For example, it is possible to achieve four times the nominal motor torque at 0 rpm.

 

Other typical figures are a torque response of less than 1ms and a speed accuracy as good as +/- 0.1% of rated rpm even though no separate sensor is mounted on the motor. The Emotron VFX variable speed drives are based on direct control of magnetic flux and torque.

 

The high accuracy of the flux and torque estimator makes it possible to up to 400% nominal torque from a motor even at 0 rpm. The torque /current ratio is linear above nominal torque, i.e. 200% current results in 200% torque compared with approximately 150% obtained with conventional inverters. To achieve such high torque the variable speed drive must match the required peak current

 

 Benefits of direct torque control