Page 86 - Apprentice Manual_Neat

S3-Q76.) The output leads on a generator should always be connected to a:

a.) Over current relay
Overload relays are used on motors and are a thermal device. Not desirable on the output of a
generator.
b.) Voltage sensing relay
No such device is used in power generation.
c.) *Current limiting device
Correct. Current must always be limited to prevent damage or catastrophic failure. Circuit
breakers can clear a fault in approximately three alternations. Fuses can clear a fault in less
than one alternation or less than ½ cycle.
d.) Ground fault relay
GFIs may be necessary in some applications, however, the first line of defense is a always current
limiting.

S3-Q77.) Generator shaft misalignment causes _____________ and increases with _______.

a.) Engine brake failure, load
Is wrong because there is no engine brake on generators, but the word “load” is correct
b.) *Vibration, engine speed
Is correct because as engine speed increases, one order vibration increases. The use flex-disc
coupling minimizes the problem somewhat.
c.) Vibration, engine load
Is wrong because engine load relates to crank bending more whereas vibration relates to engine speed.
d.) Imbalance , engine size
Is wrong because while imbalance is a factor in vibration, engine size has nothing to do with
misalignment other than the larger the weight to be turned, the less concentricity intolerance is
allowed.

Section 4: Engine Generator Instrumentation and Controls

S4-Q78.) A magnetic pick-up

a.) Can detect zero speed
This device requires motion for detection.
b.) Is an electronically controlled semiconductor device
It operates on the principle of induction and the changing of flux.
c.) *Works with ferrous metal gear teeth
Correct. As the gear teeth pass the pick-up, it detects a change in magnetism and produces a
pulse.
d.) Actually has nothing to do with magnetism at all
It operates on the principle of induction and the changing of flux.

S4-Q79.) Engine controllers require what instruments to monitor engine conditions?

a.) System controller
Sensors and engine controllers may be wired directly and not use a controller.
b.) Motion sensors
Usually the engine controller is looking for faults, not motion related parameters.
c.) *Engine protective devices
Correct. Engine protective devices will allow the controller to shut down when necessary or change
performance.
d.) Remote annunciator
Annunciators are not required for the controller to do its job, just to notify the operator.

EGSA Apprentice Certification Program Study Guide - Page 78