Electricidad 9

A diesel driven emergency generator is prevented from being paralleled with the ship's service generators by __________.

• an electrical interlock system

• an automatic paralleling trip switch

• the synchronizing oscilloscope

• the reverse current relay

As load is added to a DC shunt motor, the motor will __________.

• speed up

• maintain the same speed

• slow down slightly

• stop

The purpose of having low voltage protection for an electric motor circuit is to __________.

• prevent severe arcing or sparking

• protect against reversal of power in the main circuit

• prevent excessive current from developing as it is attempting to deliver its required horsepower

• prevent the motor from overspeeding

Proper maintenance of a D.C. motor's commutator includes __________.

• side-cutting the copper segments and undercutting the mica

• coating the copper surface with light machine oil for the first four hours of operation

• baking the armature in an oven at 350°C for 8 hours annually

• all of the above

Which of the following is a characteristic of fractional  horsepower repulsion start motors?

• They start with a rotating stator field.

• The short circuiting ring is removed from the commutator while starting.

• The brushes are removed from the commutator while starting.

• They have a low starting torque.

When troubleshooting a lead-acid storage battery, a weak or dead cell is best detected by __________.

• comparing the specific gravity of the electrolyte in each cell

• taking an open circuit voltage test of individual cells

• visually inspecting the electrolyte levels of each cell

• taking each cell's temperature with a calibrated mercury thermometer

What is the approximate discharge voltage produced by one wet cell of a nickel-cadmium battery?

• 1.25 volts

• 1.5 volts

• 2.2 volts

• 6.0 volts

Which of the devices listed is indicated by the electronic  symbol lettered as "A", shown in the illustration?

• Thyristor

• Diode

• Capacitor

• Transistor

Electrical power loss due to hysteresis is a result of __________.

• arcing at the brushes

• pulsating terminal current

• heat generated by magnetic polarity reversals

• excessive field current

If a small electric motor is immersed in salt water it should be __________.

 I.  washed in fresh water and thoroughly dried
 II. initially started with reduced voltage

• I only

• II only

• both I and II

• neither I or II