Page 9 - Industrial Technology EXTRA 15th March 2021

Lower starting torque The starting current (red line) can be 500-600% of rated
KEB’s ASCL motor control algorithm has proven motor current.
effective many times over in shredder applications.
The first benefit of using a KEB VFD compared to In a loaded scenario (150% of rated) KEB’s
line-starting is the reduction in motor starting ASCL increases the output frequency to the motor to
current. A line-fed current will draw approximately compensate for the speed reduction. A higher speed
500-600% of motor rated current during start-up, helps the shredder’s inertia to ride through more
which can cause issues with the mains and other material and avoid hitting the critical breakdown
connected electrical loads. torque.
By contrast, a KEB VFD-started motor will ramp
up the voltage and frequency in a controlled Locked rotor scenario
manner, thereby keeping the current to a minimum. As the shredder loading is increased, the induction
motor will slip more and more until it reaches the
Better speed regulation breakdown torque. At that point, the motor will lose
A good example of the KEB speed regulation at torque and the speed will quickly drop to 0 rpm.
work is evident in the scenario where material has
entered the shredder. Line fed induction motors will KEB’s ASCL motor control algorithms provide better speed
slow (slip) thereby increasing the shaft torque. regulation under load.

March 2021 • INDUSTRIAL TECHNOLOGY EXTRA • p9