Electrical Equipment Report

8/13/2019 Electrical Equipment Report

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UNIT 3

ELECTRICAL EQUIPMENT


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What is a magnetic line voltage motor starter? An electromagnetic switch with a running overload protection

(electric motor control 9thedition page 23)

How many poles are required on motor starters forthe following motors

a. 240-volt, single-phase induction motor 2

b. 440-volt, three-phase induction motor 3



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What causes the AC hum or chatter in ACelectromagnetic devices?

Because were using AC voltage which has 0 voltage. When it reaches0 there is no pull on the armature causing it to drop due to gravity

and be pulled back in due to the solenoid principle.(electric motor control 9thedition page 27)

What is the phase relationship between the flux inthe main pole of a magnet and the flux in the

shaded portion of the pole? 90 degrees apart



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In what AC devices is the principle of the shadedpole used?

Magnetic starters on contactor section Relays


What does the electrician look for to remedy thefollowing conditions:

B. Chatter or Relay


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What type of protective enclosure is most commonlyused and what is its NEMA number?

NEMA 1 General purpose


What advantage is there in using combinationstarters?

We have both disconnecting switch and starting protection(electric motor control 9thedition page 40)


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What safety feature does the combination starterprovide that individual motor starting assemblies

do not? Starting protection: fuses and circuit breakers


List the probable causes if the armature does not

release after the magnetic starter is de-energized Mechanical binding, The air gap in magnet is destroyed, Gummy

substance on magnet faces, Weak tip pressure, Contact tip welding



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The magnetic starter is held closed electrically magnetically

(http://en.wikipedia.org/wiki/Magnetic_starter )

When a motor starter coil is de-energized gravity and spring tension open contacts


An AC magnet may hum excessively due to All of these (improper alignment, foreign matter between contact

surfaces, loose laminations)

http://en.wikipedia.org/wiki/Magnetic_starterhttp://en.wikipedia.org/wiki/Magnetic_starter


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AC magnets are made of laminated iron to reduce heating effect

(http://www.ask.com/answers/309497461/why-are-ac-magnets-made-of-laminated-iron)


The purpose of overload protection on a motor isto protect the

motor from sustained overcurrents

http://www.ask.com/answers/309497461/why-are-ac-magnets-made-of-laminated-ironhttp://www.ask.com/answers/309497461/why-are-ac-magnets-made-of-laminated-ironhttp://www.ask.com/answers/309497461/why-are-ac-magnets-made-of-laminated-ironhttp://www.ask.com/answers/309497461/why-are-ac-magnets-made-of-laminated-ironhttp://www.ask.com/answers/309497461/why-are-ac-magnets-made-of-laminated-ironhttp://www.ask.com/answers/309497461/why-are-ac-magnets-made-of-laminated-ironhttp://www.ask.com/answers/309497461/why-are-ac-magnets-made-of-laminated-ironhttp://www.ask.com/answers/309497461/why-are-ac-magnets-made-of-laminated-ironhttp://www.ask.com/answers/309497461/why-are-ac-magnets-made-of-laminated-ironhttp://www.ask.com/answers/309497461/why-are-ac-magnets-made-of-laminated-ironhttp://www.ask.com/answers/309497461/why-are-ac-magnets-made-of-laminated-ironhttp://www.ask.com/answers/309497461/why-are-ac-magnets-made-of-laminated-ironhttp://www.ask.com/answers/309497461/why-are-ac-magnets-made-of-laminated-ironhttp://www.ask.com/answers/309497461/why-are-ac-magnets-made-of-laminated-ironhttp://www.ask.com/answers/309497461/why-are-ac-magnets-made-of-laminated-ironhttp://www.ask.com/answers/309497461/why-are-ac-magnets-made-of-laminated-ironhttp://www.ask.com/answers/309497461/why-are-ac-magnets-made-of-laminated-iron


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The number of magnetic starter poles refers to the number of power, motor, or load contacts


Motors may burn out because of all of the above (overload, high ambient temperatures, poor

ventilation)

(electric motor control 9thedition basis on chapter 1 introduction)


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The purpose of a shading coil on an ACelectromagnetic pole tip is to

D. prevent chattering

(http://answers.yahoo.com/question/index?qid=1006041829495)


The current drawn by a motor is B. an accurate measurement of motor load

(2010 edition electric motors and drives Technical Manual)
http://answers.yahoo.com/question/index?qid=1006041829495http://answers.yahoo.com/question/index?qid=1006041829495


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Thermal overload relays react to A. high ambient temperatures and excessive heating due to overload

currents


The thermal relay heating element is selected C. From the motors FLA and manufacturers selection chart



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When the reset button does not reestablish the controlcircuit after an overload, the probable cause is

B. the overload trip has not cooled sufficiently

If an operator pushes a start button on a 3-phaseinduction motor and the motor starts to hum, but

not run, the probable trouble is A. one fuse is blown and the motor is single phasing


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A combination starter provides all of these (disconnecting means, overload protection, short-circuit

protection)


Vacuum contactors A. are quieter in operation than standard contactors


What does IEC stand for? D. International Electrotechnical Commission



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