Motors saturable reactors

Saturable reactors, which are adjustable by a small dc signal, have also been used for both primary (stator) and secondary (rotor) control. In the primary they control motor voltage and therefore torque. In combination with fixed secondary resistors and feedback from a tachometer, this system can be used for precise speed and torque control of cranes, hoists, etc. Even reversing can be accomplished by using two saturable reactors in each of two (of three) phases. Other combinations of fixed or saturable reac tors in the primaiy and/or secondaiy, all combined with secondary resistors, provide a wide range of capabiUties and flexibihty for the wound-rotor motor. 

Thyristors have been replacing saturable reactors they are small, efficient, and easily controlled by a wide variety of control systems. A modern crane control drive uses fixed secondary resistors and two sets of primaiy thyristors (one set for hoist, one for lower). With tachometer feedback for speed sensing, the control for the motor provides speed regulation and torque hmiting in both directions, all with static-devices. A wide variety of control systems is possible the control should be designed for the specific application. 

Component Electric Hoist Motors and Controls. Both hoists have enclosed, nonventilated, 220/440-V, three-phase, 60-Hz, 1200-rpm (rev/min) motors. The control used on hoist motions is referred to as the static stepless magnetorque control on the manufacturer s drawings. With this control, drive motor torque is controlled by means of fixed resistors and saturable reactors in the... 

Electric hoist motors Fixed resistors Saturable reactors Motor secondary circuits Induction master Magnetic amplifiers Motor shaft extension... 

A static controller may be used to control the operating speeds of wound-rotor motors. In one method, a controlled saturable reactor is placed in the rotor circuit with the accelerating resistance. For fixed operating speeds, reactor saturation (which controls the motor speed) can be varied using a control resistor. Static controllers can also be used to reverse the direction of motor rotation by placing saturable reactors in the motor primary circuit rather than reversing contactors. Controlled reactor saturation directs the reversal of the motor rotation. 

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