Introduction to Electrical Power and Power Electronics

407Variable-Frequency Drives

the low end of the 0.7–0.9 range that many industry standards allow. The cyclocon-

verter is an old converter technology, whose time had passed for a while but is now

getting new attention for certain benets. It works well in icebreakers and dynamic

positioning ships requiring very high torque at low speed. However, its use is limited

for output frequency up to 30%–40% of the supply frequency.

DC motor drive. The dc motor speed is controlled simply by changing the motor

terminal voltage while maintaining the constant eld current to maintain constant

air gap ux. Unlike the ac motor drive, the dc motor drive (Figu ...