DC Motors
List the three basic types of DC Motors
2. Shunt
3. Compound
The output voltage of a shunt generator is usually controlled by the amount
Field excitation current
The voltages of a two-phase system are _ degrees out of phase with each other
90
A device that converts electrical input into mechanical output is called
Motor
The amount of CEMF produced in the armature of a DC motor is proportional to three factors
1. Number of turns of wire in the armature
2. The strength of the magnetic field of the pole pieces
3. The speed of rotation of the armature
In a generator, the series field diverter is also called the
Series field shunt rheostat
A one-horsepower motor will have a full-load current of _ amperes when connected to 90 volts dc.
12.2
What limits the amount of current flow through the armature when power is first applied to the motor?
Some DC servomotors have square wave input voltage. To vary the motor speed, the on and off time ratio of the square wave is varied. This is called _ modulation
Pulse-Width
List two ways to reduce current to the armature of a DC motor
1. Connect resistance in series with the armature
2. Use an electronic controller to supply variable voltage to the armature circuit separately from the field
In a compound generator, the setting of the amount of currents in series and shunt field windings determines the _
Compounding
The temperature ratings of devices such as circuit breakers, fuses, and terminals are found _
in UL product directories
In a universal motor, inductive compensation can be used when the motor is connected to
The DC motor, known as a "Constant speed motor" is the _ motor
Shunt
When the field winding of a DC motor is connected in parallel with the armature, the motor is called a
A compound has both series and shunt field windings. When those windings are connected so they aid each other in the production of magnetism, that connection is called _ compound
Two-phase motors that are especially designed for _ applications use the same rules for determining full-load currents as single-phase motors
Low speed-high torque
What is the name of the protective device that is connected to in series with the shunt field and found on most large compound DC motors ?
Hermetically sealed resistance-start and capacitor-start motors use three basic types of starting relays list them
1. Hot Wire relay
2. Current relay
3. Solid-state starting relay
Brushless DC motors that require very smooth operation such as grinders that produce a finished surface are powered by _ waves
Sine
The output voltage of series generator is set when the load is
Connected
Most common squirrel-cage motors used in industry actually fall into the design _ classification
B
The temperature ratings of devices such as circuit breakers, fuses, and terminals are found
A_ motor operates on the principle that like magnetic poles repel.
Repulsion