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Electricity 4: AC/DC Motors, Controls, and Maintenance

Jeffrey J. Keljik

Chapter 24

Single-Phase Motor and DC Motor Installation and the National Electrical Code - all with Video Answers

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Chapter Questions

Problem 1

Describe the difference between motor short-circuit protection and motor overload protection. _____________________________________________________

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Problem 2

When determining the short-circuit protection percentage for a 1 hp single-phase motor that has a name plate current of 14.7 amps, what value of current would you use?
_____________________________________________________________

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Problem 3

If a single-phase motor supplied by a two-wire, 120-volt circuit with one conductor grounded, needed an overload unit, in which conductor would the unit be installed?
____________________________________________________________

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Problem 4

An impedance-protected motor would be protected against overcurrent by the
____________________________________________________________.

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Problem 5

Where installing a single-phase motor that is not Z protected, the short-circuit ground-fault protection is rated at ________________% of ________________ value when using an inverse time breaker.

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Problem 6

If you have to install a constant voltage DC motor using an inverse time breaker for short-circuit protection, then use a breaker rated at ________________ % of Code book value.

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Problem 7

The branch-circuit conductor that supplied power to a single-phase cap start motor should be rated at ________________ % of the ________________ ________________ value for the motor at connected voltage and rated hp.

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Problem 8

The standard controller for a motor used in residential garbage disposal is a ________________.

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Problem 9

A single-phase air-conditioner outdoor condenser/compressor would have a ________________ connected within sight of the unit.

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Problem 10

If a continuous duty motor more than 1 H.P. has a thermal protector protecting it from overload and the service factor is 1.15, then the trip value of the OL would be ________________% of the nameplate current of the motor.

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