Electric Motor Control
10th Edition
ISBN: 9781133702818
Author: Herman
Publisher: CENGAGE L
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Chapter 36, Problem 2SQ
Do secondary resistors on starters with three or more steps of acceleration have more or less current inrush than those with two steps of acceleration?
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question 20:
Do we need an add-on auxiliary contact on motor starter 2 to make this circuit work?
a
Yes
b
No
A single-phase electric motor is connected to a 240-volt, 30-ampere circuit. The motor nameplate indicates that the full-load current draw of the motor is 21 amperes. The motor is connected to an inertia load (a large flywheel) that requires several seconds for the motor to accelerate to full speed. Because of the long starting time, the motor causes the circuit breaker to trip before the load has reached full speed. Your job is to connect a resistor in series with the motor during the starting period that will limit the starting current to 90% of the circuit-breaker rating. An ammeter indicates that the motor has a current draw of 64 amperes when power is first applied to the motor. Determine the ohmic value and wattage rating of the resistor that should be connected in series with the motor during the starting period.
Determine the following based on the wiring diagram illustrated in figure 8 on worksheet 5 if it is that of a 6-pole, non-salient pole design, 60-Hz, 3-phase AC generator stator that has 10 volts induced in each coil.
What is the total number of coils on the stator?- A- 3, B- 18, C-54, D- 108
If the total number of coilson the stator are divided equally between the three phase belts how many coils are there in each phase? A-3, B-18, C-54, D-108
What is the total voltage induced in each of the three phase belts? A-30V, B-180V, C-312V, D-none of the above.
Chapter 36 Solutions
Electric Motor Control
Ch. 36 - Are the secondary resistors connected in three...Ch. 36 - Do secondary resistors on starters with three or...Ch. 36 - Does reversing the secondary rotor leads mean that...Ch. 36 - If one of the secondary resistor contacts (S2)...Ch. 36 - In Figure 362, how many different interlocking...Ch. 36 - Referring to Figure 364, why is it not possible to...Ch. 36 - Prob. 7SQCh. 36 - If there is a locked rotor in the secondary...Ch. 36 - Why is it necessary to remove the jumpers in...Ch. 36 - Prob. 10SQ
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- If an armature has a resistance of 0.5 ohm, what series resistance must be used to limit the current to 30 amperes across a 230-volt circuit at the instant of starting? What is the power rating?arrow_forwardThis test allows to determine the resistance of the windings?arrow_forwardAt standstill condition, the back emf is zero, so the motor can be safely turned ON without a starter. Select one: O True O False?arrow_forward
- What section of the Code emphasizes the fact that all circuiting must be done so as to avoid the damaging effects of induction heating? ____________arrow_forwardYou are working as an electrician installing fluorescent lights. You notice that the lights were made in Europe and that the ballasts are rated for operation on a 50-Hz system. Will these ballasts be harmed by overcurrent if they are connected to 60 Hz? If there is a problem with these lights, what will be the most likely cause of the trouble?arrow_forwardD.a- A knocking sound that's coming from a pump is normally caused byA. a faulty coupling.B. a broken impeller.C. a leaking seal.D. pump cavitation.D.b- A DC motor will normally require that you replace which one of the following components on a regularschedule?A. BrushesB. ArmaturesC. GearsD. BearingsD.c- You're doing a PM inspection on a small chain-drive system. You see one side of the sprockets is shinywhile the opposite side is dull. This means that theA. chain is the wrong size.B. sprockets are worn.C. chain is worn.D. sprockets are misaligned.arrow_forward
- Which type of stator winding has two windings in parallel?arrow_forwardWhat size conductor would be required to supply three motors connected to a 440-volt, 3-phase branch circuit? Motor #1 is a 50-horsepower, code B induction motor; motor #2 is a 40-horsepower, code H induction motor; and motor #3 is a 50-horsepower, code J induction motorarrow_forwardSelect the best answer for each of the following. The purpose of overload protection on a motor is to protect the a. motor from sustained overcurrents. b. wire from high currents. c. motor from sustained overvoltage. d. motor from short circuits.arrow_forward
- how many turnsarrow_forwardA starter turns very slowly and has excessive cranking current draw. When removed from the vehicle and bench tested, the starter spins normally and current draw is within specifications. Technician A says poor battery connections may be the cause. Technician B says an internal engine problem may be the cause. Who is correct?arrow_forwardFor the Starting Up the Power Station Simulator Why are certain operations blocked by isolatorsarrow_forward
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