Electric Motor Control
10th Edition
ISBN: 9781133702818
Author: Herman
Publisher: CENGAGE L
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Chapter 51, Problem 7SQ
To determine
Explain why there is no danger in reversing of motor after it is stopped by braking.
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Explain why synchronous motor doesn’t have any self-starting torque. Demonstrate some measures to make it self-starting.
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Electric Motor Control
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- 1. At what speed will a synchronous motor operate if it has 10 poles and is connected to a 50-cycle source? a 25-cycle source? a 60-cycle source?arrow_forwardDo the question belowarrow_forward1- What causes a three-phase motor to run backwards? 2- How we can reverse the direction of the induction motor? 3- What are the advantages of changing the direction of an induction motor for a 3-phase? 4- What is a forward reversing motor control circuit? 5- What is the application of the forward and reverse motor? 6- Why do we change the direction of the rotation of a 3-phase induction motor?arrow_forward
- The industry standard for reversing the rotation of a wound-rotor motor is to _______ a. Reverse T1 and T3 b. Reverse M1 and M3 c. Reverse T2 and T3 d. Reverse M2 and M3arrow_forwardExplain why the use of switching drives can be problematical when driving an inductive load, and how any problems may be overcomearrow_forwardAssume all of the timers are set for a 3 second delay. When the start button is pressed, nothing happens. None of the motors start. Which of the following could NOT cause this problem. a Overload contact OL1 is open b 1CR relay coil is open c 2CR relay coil is open d The stop button is openarrow_forward
- While operating at full load in all features, the synchronous motor changes characteristics when the load is completely removed.does it? Explain (you are expected to answer this question using the V-curve).arrow_forward3. A 415 V, 250 HP, six-pole, 50 Hz induction motor has a full load slip of 4%, an efficiency of 89 %, and a power factor of 0.89 lagging. At start up, the motor develops 175 % of FLT, but draws 7 times full load current (on rated voltage). The motor must develop at least FLT at switch on, to ensure successful starting. If the fault level at the 415 V switchboard is 15 MVA, calculate the maximum length of cable which may be used to connect the motor, if the cable has reactance 0.005 2/metre. The above motor is to be corrected to operate at 0.95 lagging power factor. Calculate the amount of capacitance required to be connected at the stator terminals of the machine to achieve this, and the resulting capacitor values. 4.5 m, 12.8 kVAr per phase, 0.7 mFarrow_forwardHow can the direction of rotation of a DC shunt motor be reversed? * Your answerarrow_forward
- Explain how does the current will be reduced during the starting of the motor.arrow_forwardInduction motor speed control technique which is not recommended to be used at low speed is O V-I control O stator voltage control O slip power control O V-F controlarrow_forwardIN Counter-Current Breaking o f a 3-Phase Induction Motor(Reversing the Operation o f a 3-Phase Induction Motor) How it was insured in the control circuit as to avoid the operation of both positiveand negative sequences simultaneously?arrow_forward
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