Electric Motor Control Final Exam Questions and Answers 2023
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Course
Electric Motor Control
Institution
Electric Motor Control
motor connections factors - Answer- horsepower, service factor,marked temperature rise, voltage, full load current rating and nema code letter
Synchronous motor advantage - Answer- they can provide power factor correction for themselves
Squirrel cage induction motors are used - Answer- to pow...
Electric Motor Control Final Exam Questions and Answers 2023
motor connections factors - Answer- horsepower, service factor,marked temperature rise, voltage, full load current rating and nema code letter
Synchronous motor advantage - Answer- they can provide power factor correction for themselves
Squirrel cage induction motors are used - Answer- to power most of the machines throughout industry
motor starters can be divided into two classes - Answer- IEC and NEMA
NEMA starters range - Answer- 00-8
NEMA size 00 - Answer- is rated to control a 2-horsepower motor connected to a 460 volt, three phase power supply
NEMA size 8 - Answer- Will control a 900 horsepower motor connected to a 460 volt, three phase power supply
semiautomatic controls - Answer- characterized by the use of push buttons, limit switches, pressure switches and other sensing devices to control
manual controls - Answer- simple devices that are hooked onto the line of a motor
Automatic controls - Answer- similar to semiautomatic controls but operator does not have to initiate control
across the line starting - Answer- accomplished by connecting the motors directly to the power line
ramping - Answer- requires a motor to start at a low speed and accelerates to full speed
over time
Simplest method of stopping - Answer- disconnect power line
Normally open push button - Answer- Normally closed push button - Answer- When components are shown connected by a dashed line in a schematic diagram - Answer- it indicates that the components are mechanically connected together Normally open liquid flow switch - Answer- float switch - Answer- temperature switch - Answer- disconnect switch - Answer- circuit breaker - Answer- on delay timer - Answer- Current transformer - Answer- air core transformer - Answer- Dual voltage transformer - Answer- Auto transformer - Answer- First step of trouble shooting - Answer- determine whether the motor is overloaded
Shorted windings in the motor - Answer- can cause the motor to draw excessive current
Current flow in a 3 phase motor should - Answer- all be the same
manual starters that are installed in a switch box - Answer- more susceptible to ambient temperature problems
Motors have a current draw of - Answer- 300-800% more than the full load current
Locked rotor current - Answer- Motor current starting
Overload relays are generally set to trip at - Answer- 115%
Solder melting overload relay - Answer- activates from the melting of solder
Bimetal strip - Answer- constructed by bonding to different types of metal together
dashpot overload relays - Answer- basically a container, a piston and a shaft
if the motor is overloaded - Answer- the magnetic field will be strong enough to continue
drawing current from the shaft
bridge type relay - Answer- operates by drawing a piece of metal or plunger inside a coil
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