Torque ramp technology

Emotron MSF softstarters

Emotron's first softstarter was launched in 1983 and the torque control was introduced in 1999

The logic based torque control system relies on a special designed control algorithm to maintain constant accelerating and decelerating torque. The algorithm uses information about motor voltage, motor flux, current and voltage zero-crossing to determine the torque and power factor. From this, the softstarter calculates the actual shaft torque.

 

The initial torque and end torque are entered to Emotron MSF softstarter which the torque controller uses, along with the entered torque ramp time, to generate a desired motor torque. The torque controller is then used to control the thyristor firing, according to the actual motor torque versus the desired value. The motor torque is no longer strictly dependent on an applied motor voltage and the speed torque characteristics of the motor, but is increased according to a timed ramp.

 

The upper curve is start current and the lower speed/acceleration

 

Emotron MSF

Voltage ramp start

Direct on line (DOL) start

 

 

 Benefits of torque control