-
What are the two major types of induction motors used aboard ship?
Polyphase (3-phase), single-phase.
-
Where does the electromagnetic induction take place in an induction motor?
Between the stator and the rotor under operating conditions.
-
Almost all large motors found aboard naval ships are of what design?
Polyphase.
-
A motor used to provide an electronic cooling fan normally would be of what design?
Single-phase.
-
The driving torque of an AC motor is derived from what?
The reaction of current-carrying conductors in the magnetic field.
-
In a polyphase motor torque is developed by interaction between what two things?
The rotor's magnetic field and the stator's revolving magnetic field.
-
What balances the rotor on a polyphase motor?
Balancing Disks.
-
On a polyphase motor, the 3-phase stator winding receives power from what external source?
Via a controller.
-
What protects a vertically mounted polyphase motor from moisture?
A Drip proof Cover.
-
How is the rotor brought up to speed on a single-phase motor?
By special design of the stator winding.
-
What are the three types of identification used to determine single-phase motor application?
Split-phase, capacitor, universal.
-
What type of Single-phase motor uses a displacement of 90 electrical degrees between the starting and main windings?
Split-phase.
-
The starting torque of a capacitor motor may be as much as what percent of full torque?
350 Percent.
-
In a capacitor motor the capacitor is connected in series to what?
The starting windings.
-
A universal motor is used for what application aboard ship?
Portable tools.
-
What type of Single-phase motor can be operated from either DC or single-phase AC power?
universal motor.
-
What single-phase motor is constructed with the main field connected in series with an armature?
universal motor.
-
When disassembling a motor, what is recommended to use to protect the windings from damage?
Waxed paper placed between the rotor and the stator.
-
Motors installed aboard ship are designed to operate within what voltage variation as indicated on the motor nameplate?
Plus or minus 10%
-
AC motors are designed to operate within what frequency variation as indicated on the motor nameplate?
Plus or minus 5%
-
Almost all AC motors aboard ship which are above fractional horsepower size are of what design?
Polyphase induction.
-
What type of AC motor has a primary winding which is connected to the power supply, and a secondary winding which has no electrical connection to the power supply?
polyphase induction motor.
-
What induces voltage in the secondary winding of a polyphase induction motor?
The rotating magnetic field.
-
The speed of rotation of the magnetic field is know as what?
Synchronous speed.
-
In relation to synchronous speed, the rotor of an induction motor runs at what speed?
Less than synchronous speed.
-
The difference between synchronous speed and rotor speed on an induction motor is known as what?
Slip.
-
What type of induction motor has a rotor winding made of longitudinal bars connected to and short circuited by rings at the ends of the rotor?
A squirrel gage induction motor.
-
What energizes the rotor winding in a squirrel gage induction motor?
Induction produced from the slip frequency.
-
What type of induction motor rotor is constructed of individually insulated coils?
Wound-rotor induction motor.
-
What type of DC motor field coil is connected in parallel with the armature?
Shunt motor.
-
A DC motor that has one set of field coils connected in parallel with the armature and another set connected in series with the armature is known as what type of DC motor?
Compound motor.
-
The life of electrical insulation is reduced by approximately what, when the insulation is operated at 10 degrees C in excess of design temperature?
Reduced by 1/2.
-
Convert Fahrenheit to Centigrade and Centigrade to Fahrenheit?
C = 5(F-32)
-
When making temperature measurements either by thermometer or resistance method, they should be taken at what interval?
Every 2-3 minutes.
-
Motors should be measured for insulation resistance at what periodicity?
Every quarter.
-
Overlubrication of a motor or generator causes what?
Overheating and deterioration of insulation.
-
Shock mounts should be visually inspected at what interval?
Every six months.
-
What is an indication of a deteriorated shock mount?
A significant decrease in the distance between the framework of the equipment and the foundation.
-
When using electric lamps for drying purposes, what is the required amount of heat?
5 to 10 degrees F. above the ambient air temperature.
-
What is used to prevent moisture buildup in motors, when they are idle in excess of two weeks with no power available for heat lamps?
Desiccant.
-
What type of desiccant is recommended for use on squirrel gage induction motors?
Selica gel type.
-
Clay type desiccant is used for what type of equipment?
Equipment that uses carbon brushes.
-
When using compressed air to dry motors and generators what is the maximum allowable pressure?
30 PSI.
|
|
