Electric Motor Control
10th Edition
ISBN: 9781133702818
Author: Herman
Publisher: CENGAGE L
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Chapter 3, Problem 15SQ
To determine
Choose the best option by which the magnetic starter closes the switch.
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3. i. Write the working principle of Permanent Magnet Moving
Coil instrument mention the importance spring used.
ii. Explain how a single PMMC instrument can be used as
ammeter and voltmeter.
5) The deflecting torque of an ammeter varies as the square of the current flowing through it. If a current of 10
A produces a deflection of 90°, what deflection would occur for a current of 5 A when the instrument is (a)
spring controlled and (b) gravity controlled?
[Ans. (a) 22.5°, (b) 14.5°]
Explain how DOL magnetic starter works step by step with diagram and pictures.
Chapter 3 Solutions
Electric Motor Control
Ch. 3 - Prob. 1SQCh. 3 - How many poles are required on motor starters for...Ch. 3 - If a motor starter is installed according to...Ch. 3 - Using the time limit overload or the dashpot...Ch. 3 - What causes the AC hum or chatter in AC...Ch. 3 - What is the phase relationship between the flux in...Ch. 3 - In what AC and DC devices is the principle of the...Ch. 3 - What does the electrician look for to remedy the...Ch. 3 - What type of protective enclosure is most commonly...Ch. 3 - What advantage is there in using combination...
Ch. 3 - What safety feature does the combination starter...Ch. 3 - Prob. 12SQCh. 3 - How is the size of the overload heaters selected...Ch. 3 - What type of motor starter enclosure (include NEMA...Ch. 3 - Prob. 15SQCh. 3 - Prob. 16SQCh. 3 - Prob. 17SQCh. 3 - Prob. 18SQCh. 3 - Select the best answer for each of the following....Ch. 3 - Prob. 20SQCh. 3 - Prob. 21SQCh. 3 - Select the best answer for each of the following....Ch. 3 - Prob. 23SQCh. 3 - Select the best answer for each of the following....Ch. 3 - Select the best answer for each of the following....Ch. 3 - Select the best answer for each of the following....Ch. 3 - Select the best answer for each of the following....Ch. 3 - Prob. 28SQCh. 3 - Select the best answer for each of the following....Ch. 3 - Prob. 30SQCh. 3 - Prob. 31SQCh. 3 - What is the difference between a grounded control...Ch. 3 - A control transformer has a primary voltage of 480...
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- The two basic kinds of electricity are: Static and stationary. Current and resistance. a. b. Static and dynamic. d. Dynamic and moving. C. Electromotive force (EMF) causes electrons to flow through a circuit. EMF is measured in: Volts. b. Amperes. Current, Resistance a. C. d. A complete circuit is made up of A generator, electron flow. and voltage source. a. A source of electricity, a conductor, and a consuming device. b. A consuming device, a load, and a conductor. d. Electron flow, resistance, and a load. C. You can get an electrical shock: When some part of your body becomes part of an electric a. circuit. b. If you touch both wires of an electric circuit. C. If you touch one wire of an energized circuit and ground. d. All of the above. Electricity can cause fires: Because of defective or misused electrical equipment. When wires are improperly spliced or connected. When wires are improperly connected to outlets or a. b. C. switches. d. All of the above.arrow_forwardHow can the polarity of an electromagnet be determined if the direction of current flow is known? 2. Define the following terms: 3. flux density 4. Permeability 5. Reluctance 6. Saturation Unit 13 Magnetic Induction 7. Name three factors that determine the amount of induced voltage in a coil. 8. What is the effect on induced voltage of adding more turns of wire to a coil? 9. Into how many time constants is an exponential curve divided? 10. Each time constant of an exponential curve is equal to what percentage of the maximum amount of charge? 11. An inductor has an inductance of 0.025 H and a wire resistance of 3 . How long will it take the current to reach its full Ohm's law value? Unit 15 Alternating Current . 12 What is the most common type of AC waveform? 13 How many degrees are there in one complete sine wave? 14 At what angle does the voltage reach its maximum negative value on a sine wave? 15 A sine wave…arrow_forwardWhat is clamper? Briefly explain its working.arrow_forward
- 9- The example of electric ciruit of machine parts is a. Armature core b. Field poles c. commutator d. Yokearrow_forwardA. The brushes used in a DC generator a) ride against the commutator segments. b) are made from material softer than the commutator segments. c) are generally marked Al and A2 d) all of the above B. A magneto is a DC generator that uses for its pole pieces. a) electromagnets b) permanent magnets c) either "a" or "b" d) neither "a" nor "b"arrow_forward5- Voltage control is also called a. Ward leonard control b. Armature control c. Flux control d. Field controlarrow_forward
- Calculate the voltage of the DC source and the stored field energy of the actuator illustrated infigure 1.1. The dimensions of the magnetic circuit proposed in shown figure 1.2. The core of the magnetic circuit is made of cast steel material whose B-H characteristics is illustrated in figure 1.3. The coil in figure 1.1 has 250 turns, and the coil resistance is 5 ohms. For a given length g=5mm, a Dc source is connected to the coil to produce a flux density of 1 Tesla in the air gap.arrow_forwardS magnet retort stand coil voltmeter 17. Which of the following statements is TRUE when the magnet is dropped inside the solenoid? * A. The induced voltage is zero when the magnet is halfway through the solenoid. B. The voltage reading increases with time until the magnet leaves the solenoid. C. The voltage reading decreases with time until the magnet leaves the solenoid. D. Maximum induced voltage occurs just before the magnet enters the solenoid. E. The magnetic flux inside the solenoid is constant as the magnet is dropped from rest.arrow_forwardDC current produces Select one: a. No magnetic field O b. Dynamic (Time-varying) magnetic field O c. Static magnetic field O d. Dynamic (Time-varying) electric fieldarrow_forward
- parte A • Develop and explain the electrical schematic for the excitation coil in series.• Develop and explain the electrical schematic for the excitation coil in parallel.• Mention or cite examples about what use or application these 2 settings are used for.arrow_forwardDraw a symbol for a magnetic starter.arrow_forwardSelect the DC generator used for arc welding. With an elegant drawing explaining its operation. Mention their advantages and disadvantagesarrow_forward
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