Questions
Because the rotor of the servodisc motor is made from copper laminated onto a fiberglass disk, the motor is also called a
printed circuit
List three basic types of DC motors
Series, shunt, compound
T/F It is alright to operate a series motor with no load connected
False
What type of motor can develop extremely high starting torque
Series
When connecting a compound motor place the the steps that should be followed in the correct order to prevent the motor from being accidentally connected differential compound. what is the first step?
disconnect the motor from the load
Brushless DC motors that require very smooth operation such as grinders that produce a finished surface are powered by
Sine waves
List two factors that determine the amount of torque produced by a dc motor
the strength of the magnetic pole pieces. The strength of the magnetic field of the armature
A DC motor is connected to a 480-VDC line and has a current draw of 35A. The motor is operating a load that requires 625 in-lb of torque and is turning at a speed of 2000 RPM. What is the horsepower output of the motor. What is the efficiency of the motor.
19.875 HP, 88.2545 EFF
What limits the amount of current flow through the armature when power is first applied to the motor
armature resistance
What is the second step
Connect the series field and armature windings together to form a series connection
when full voltage is applied to the armature and reduced current flows through the shunt field the motor operates at
over speed
When a DC machine is used as a motor what function does the commutator perform
The commutator performs the function of a rotary switch and maintains the correct direction of current flow through the armature
A DC motor is connected to a 120-VDC line and has a current draw of 90A the motor is operating a load that requires 652 in-lb of torque and is turning at a speed of 1300 RPM. WHat is the horsepower output of the motor. What is the efficiency of the motor
13.47684HP
93.09EFF
When full voltage is applied to the both armature and the shunt field, the motor operates at
base speed
what is step four
if the motor turns in the opposite direction than is direction than is desired reverse the conncetion of the armature leads
What is the name of the protective device that is connected in series with the shunt field and found on most large compound DC motors
Field loss relay
List two ways to reduce current to the armature of a DC motor
Connect resistance in series with armature. Use an electronic controller to supply variable voltage to the armature
A DC motor is connected to a 240-VDC line and has a current draw of 14A the motor motor is operating a load that requires 143 in-lb of torque and is turning at a speed of 1250 RPM. What is the horsepower output of the motor. What is the efficiency of the motor.
2.84 HP
63.05EFF
small permanent magnet motors that have lightweight rotors are often used as
servomotors
what is step 3
turn on power momentarily to determine direction of rotation
In a compound DC motor control circuit the field loss relay will disconnect the "blank" if power is lost to the "blank"
Armature, shunt field
The amount of CEMF produced in the armature of a DC motor is proportional to three factors
The number of wire in the armature, the strength of the magnetic field of the pole pieces, the speed of the armature
T/F counter-electromotive force and back EMF are names for the voltage induced into the armature of a DC motor
True
speed regulation of a DC motor is proportional to the
armature resistance
Torque is a force that tends to cause
rotation