Electric Motor Control
10th Edition
ISBN: 9781133702818
Author: Herman
Publisher: CENGAGE L
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Textbook Question
Chapter 34, Problem 7SQ
Refer to the basic control schematic in Figure 34–4. The limit switch is shown as
a. normally open.
b. normally closed.
c. normally open held closed.
d. normally closed held open.
Fig. 34–4 Wiring diagram of manual speed regulator interlocked with magnetic starter for control of slip ring motor (three-wire control).
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c. The 3M load contacts are welded shut.
d. The normally open 3M contact between wire numbers 23 and 31 is hung closed.
20.a. A capacitive sensor is used to detect the presence of _______ objects.A. ferrousB. nonmovingC. nonconductiveD. magnetic20.b. A three-phase motor can be made to run backwards byA. connecting a resistor in series with the armature.B. reversing the control voltage connections.C. reversing three of its power leads.D. reversing two of its power leads.
Industrial Motor Controls
8.a. A typical motor speed control circuit that is controlled by an analog current loop will have a current ofA. 4-20 mA.B. 2-20 mA.C. 5-50 mA.D. 0-10 mA.8.b. Which one of the following statements is true of a disabled contact or coil?A. The disabled element has been automatically disabled due to module failure.B. The disabled element is held false by the PLC.C. A disabled contact or coil is caused by a faulty memory location in the PLC.D. A contact must be in the disabled state before it can be forced ON or OFF.
Chapter 34 Solutions
Electric Motor Control
Ch. 34 - What characteristic of wound rotor motors led to...Ch. 34 - Prob. 2SQCh. 34 - What other name is given to the wound rotor motor?Ch. 34 - Does increased resistance in the rotor circuit...Ch. 34 - Prob. 5SQCh. 34 - What is the difference between a manual faceplate...Ch. 34 - Refer to the basic control schematic in Figure...
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- A direct current motor is connected to a 250-volt DC supply. The armature has a current draw of 165 amperes when operating at full load. You have been assigned the task of connecting two resistors in the armature circuit to provide speed control for the motor. When both resistors are connected in the circuit, the armature current is to be limited to 50% of the full-load current draw. When only one resistor is connected in the circuit, the armature current is to be limited to 85% of full-load current. Determine the ohmic value and min-imum power rating of each resistor.arrow_forwardQ4/ choose the correct answer The back emf in a dc motor is ___________________?. 1-opposes the applied voltage 2- aids the applied voltage 3- opposes the field current 4- aids the armature currentarrow_forwardAnswer all or else skip the question pleasearrow_forward
- List the probable causes if the armature dos notable release after the magnetic starter is de - energized .arrow_forwardAdvance Motor Control 1. Why are contacts often disconnected in series when controlling small motors 2. Why are clapper type contactors generally used to control DC device 3. What is the purpose of FCR (field current relay)arrow_forwardFigure 24(1.) Compute the efficiency of the motor, if windage and friction losses neglected, for the circuit Q25. i diagram shown Figure 25(i), R 0.750 60A +. R-1250 M 250V Figure 25(i) ii Also calculate armature current. END OF QUESTION PAPER----- Page 4 of 4 Activatarrow_forward
- Technician A says when testing the voltage output, if the charging voltage is too high, the cause could be an open field wire from the regulator. Technician B says a loose or glazed drive belt could be the cause of too high charging voltage. Who is correct? A only B only Both A and B Neither A or B Technician A says that poor connection at the generator output wire can cause charging systems problems. Technician B says that many charging system circuits contain a circuit protection device. Who is correct? A only B only Both A and B Neither A or Barrow_forward4.a. The stop control in a three-wire control scheme stops the motor byA. increasing the resistance in the run circuit.B. shorting the starter coil.C. tripping the thermal overloads.D. disrupting current flow to the coil.4.b. An across-the-line starter does not change the speed of a squirrel-cage motor because itA. varies the internal rotor resistance.B. does not vary the line voltage.C. varies the line voltage as the line frequency increases.D. varies the pole connections at each setting.arrow_forward3.a. Which one of the following motor types uses permanent magnets in the armature or rotor?A. Stepper motorB. PM motorC. Pancake motorD. PM servo motor3.b. A type of resistance device that can be placed in a DC motor circuit and varied to limit the speed of amotor is called aA. power resistor.B. rheostat.C. potentiometer.D. variable reluctor.arrow_forward
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