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Cards In This Set
| Front | Back |
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What are the 2 main functions a motor
controller preforms.
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To disconnect the electrical power and
protect a motor from an overload condition.
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Common examples of fractional
horsepower motors are...?
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Exaust fans, garbage disposals, blower
motors, small pumps, small drill presses.
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What material is used for the surface of motor contacts and why?
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Silver Cadmium has good conductivity and a long contact life
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Normal motor operation consists of what 3 stages?
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Resting, starting and operating under load.
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What happens when a contact is opened under load?
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An arcing occurs.
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What is a magnetic motor starter?
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An electromechanical device that provides a means of starting and stopping a motor.
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Why is a magnetic motor starter not required to be located in close proximity to the machine operator?
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Because pilot devices allow the starter to be located where it poses no danger to the operator.
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List 4 examples of processes controlled by magnetic motor starters...
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Conveyor systems, pumping operations, packaging systems, paint booths and chemical mixing.
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Why is it preferable to use a control voltage that is derived from the motor voltage?
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Because both control and motor voltage will become de-energized when the motor controller disconnect is opened.
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List 8 common control voltages...
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24, 48, 120, 220, 208, 277, 480, 600
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Addtion to main motor contacts other contacts are known as what?
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Auxiliary contacts and electrical interlocks
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Configurations available for auxiliary contacts are what?
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N/O, N/C and combinations of both.
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The word "normally" means?
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It refers to the condition of the contact in a "power off" or "de-energized" state.
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What is the difference between a contactor and a motor starter?
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A motor starter has overload relays.
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What is the main function of an overload relay?
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To protect the motor winding from excessive heat caused by overload currents.
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