What are motor control centers?
What will be an ideal response?
Motor control centers are used to start and stop motors and protect them from potential overloads. They have a disconnect switch that must be located within sight of the controller and the motor. The overload protection is typically a heat-operated relay that opens the circuit when line temperatures rise. The motor circuit is closed after the overload situation has been corrected by pressing a reset button.
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A dc, separately excited motor is driven by a full-wave, SCR, ac/dc converter. The voltage on the ac side is 120 V (rms). The field constant of the motor K? = 3 Vs. At a load torque of 300 Nm and triggering angle of 40o , the motor speed is 100 rpm, and the armature current is continuous.
a. The polarities of the terminal voltage of the motor (armature voltage) are reversed, and the triggering angle is simultaneously changed. Assume that the load torque is also reversed and is equal to 300 Nm. Calculate the triggering angle that stops the motor and keeps it at the holding position. Assume that the current is still continuous. b. Sketch the speed-torque characteristics and indicate the steady state operating points before and after polarity reversal.
In a Toyota Prius regenerative braking system, how many pressure switches are used?
A) One B) Two C) Three D) Four
When is line voltage applied to an ECM motor?
A) Only when the spinning of the motor cannot generate enough voltage to keep spinning B) All the time C) Only if all the internal power storage is dissipated D) Only whenever the motor is operated
Which type of motor does not require the use of start components?
A. shaded-pole B. PSC C. CSCR D. three-phase E. both a and d