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Fourth-gen DTC promises better speed and torque control
Published:  11 August, 2014

The technology offers torque control at low (or zero) speeds – said to be particularly useful for cranes, hoists, winches or elevators, where the load needs to be started and stopped regularly without any jerking, and with a load on the cables. DTC’s torque linearity allows consistent winding levels, while its dynamic speed accuracy allows a motor to recover rapidly to a stable state after a load change.

The high-speed reference chain, which allows a motor shaft to respond to a change in speed reference within 2ms, is useful for test bench and dynamometer applications. Again, master-follower modes can be used here, along with connections to industrial fieldbuses for control and monitoring

DTC allows the ACS880 drives to control fans or pumps that are spinning at the start of the cycle, either forwards of backwards. A flying-start function catches the load and takes it under control smoothly, returning it to the desired speed.

A further DTC function is flux optimisation (or energy optimisation), which is said to provide better energy saving than other VSDs. It adjusts the motor flux to the optimal value for the load conditions at the time, thus saving energy constantly across the lifetime of an application.

ABB claims that the latest version of its DTC technology offers a torque response that is typically ten times faster than other AC or DC drives