ILT 115 final exam review UPDATED ACTUAL Questions and
CORRECT Answers
What are the two speeds that are associated with an synchronous speed and rotor speed
induction motor?
Explain the difference between the two speeds Synchronous speed is the speed at which the rotating magnetic field revolves
associated with an induction motor. around the stator, while rotor speed is the speed at which the rotor rotates. The
difference between these speeds is called slip.
What two factors determine the speed at which the Synchronous speed is affected by the number of poles and the frequency of the
magnetic field revolves around the stator of an induction applied voltage.
motor?
Explain the term "slip." Slip is the difference between rotor speed and synchronous speed. Also, as slip
increases, torque increases.
Is slip desirable or undesirable? Why? Some slip is desirable in motors, this is because torque is required to move the
load.
Prior to the advent of VFDs, name four methods of speed different pulley ratios, gear boxes, wound rotor induction motors, dedicated
control. alternators with DC prime movers.
Name the three basic types of VFDs. pulse width modulated, current source inverters, voltage source inverters.
What is the name of the section of the VFD that is The three phase power is connected to the converter stage. In this stage uses
connected to the three-phase power source? Describe rectifier diodes convert the AC to DC.
its function.
What are three names for the section of a VFD that DC link, DC filter, DC bus
produces a smooth DC?
What is the name of the section of the VFD that is The section of the VFD that is connected to the motor is the Inverter stage. This
connected to the motor? Describe its function. stage switches the DC on and off at a very high rate which makes it pulse,
simulating AC.
Explain the difference between mass and weight. The difference between mass and weight is that mass is the amount of matter
within an object, while weight is the result of the force of gravity on an object.
Explain the difference between speed and velocity. Speed is the rate of motion of an object. Velocity includes not only the rate of
motion but also the direction.
When is work done? Work is done when a force applied to and object results in movement of that
object in the direction of the applied force.
, Define electrical current. the movement of electrons
Define electrical voltage. Electrical voltage is the electrical pressure of force that causes electrons to move.
Explain the difference between resistance, reactance, Resistance is the property of an electrical circuit or component that opposes the
and impedance. flow of an electrical current. Reactance is the opposition to alternating current.
Impedance is the combination of both of these, the total opposition to current
flow.
Explain the difference between watts, VAR, and volt- Watts is the unit for True power (resistive power). VAR is the unit for how much
ampere. power is consumed by the reactive components. Volt-amperes is the combination
of the resistive and reactive powers.
What is meant by the term "locked rotor torque"? The torque that a motor develops when the rotor is at standstill and full power is
applied is called locked rotor torque.
What do we call the torque that a motor produces, when breakdown or pull out torque
operating at rated voltage and frequency, at the instance
an increase in load causes the motor to stall?
Explain the difference between dynamic and The difference between dynamic and regenerative braking is that regenerative
regenerative braking. braking systems remain connected to power to charge the circuit, while dynamic
braking has to dissipate that energy as heat.
Name at least two sources of the feedback signal. CEMF produced by the motor, tachometer-generator on the motor shaft
Explain the importance of the feedback signal. Why is it the feedback signal is needed to be compared to the control signal, the
needed? difference between the two is called the error signal.
What does the term "error signal" mean? error signal is the difference between the control and feedback signal
True or False? A higher percentage of regulation is better false
than a lower percentage of regulation.
What is meant by CEMF? cemf stands for counter electromotive force
Torque is best defined as ________________________________ rotational force
produced by a motor.
Describe the operation of a tachometer-generator. as the motor turns, the generator turns and produces a positive DC voltage
Is the voltage generated by a tachometer-generator proportional
proportional or inversely proportional to motor speed?
True or False? The summing point is that point in a circuit false
where the output from the sawtooth generator is joined
with the output form the preamplifier.
CORRECT Answers
What are the two speeds that are associated with an synchronous speed and rotor speed
induction motor?
Explain the difference between the two speeds Synchronous speed is the speed at which the rotating magnetic field revolves
associated with an induction motor. around the stator, while rotor speed is the speed at which the rotor rotates. The
difference between these speeds is called slip.
What two factors determine the speed at which the Synchronous speed is affected by the number of poles and the frequency of the
magnetic field revolves around the stator of an induction applied voltage.
motor?
Explain the term "slip." Slip is the difference between rotor speed and synchronous speed. Also, as slip
increases, torque increases.
Is slip desirable or undesirable? Why? Some slip is desirable in motors, this is because torque is required to move the
load.
Prior to the advent of VFDs, name four methods of speed different pulley ratios, gear boxes, wound rotor induction motors, dedicated
control. alternators with DC prime movers.
Name the three basic types of VFDs. pulse width modulated, current source inverters, voltage source inverters.
What is the name of the section of the VFD that is The three phase power is connected to the converter stage. In this stage uses
connected to the three-phase power source? Describe rectifier diodes convert the AC to DC.
its function.
What are three names for the section of a VFD that DC link, DC filter, DC bus
produces a smooth DC?
What is the name of the section of the VFD that is The section of the VFD that is connected to the motor is the Inverter stage. This
connected to the motor? Describe its function. stage switches the DC on and off at a very high rate which makes it pulse,
simulating AC.
Explain the difference between mass and weight. The difference between mass and weight is that mass is the amount of matter
within an object, while weight is the result of the force of gravity on an object.
Explain the difference between speed and velocity. Speed is the rate of motion of an object. Velocity includes not only the rate of
motion but also the direction.
When is work done? Work is done when a force applied to and object results in movement of that
object in the direction of the applied force.
, Define electrical current. the movement of electrons
Define electrical voltage. Electrical voltage is the electrical pressure of force that causes electrons to move.
Explain the difference between resistance, reactance, Resistance is the property of an electrical circuit or component that opposes the
and impedance. flow of an electrical current. Reactance is the opposition to alternating current.
Impedance is the combination of both of these, the total opposition to current
flow.
Explain the difference between watts, VAR, and volt- Watts is the unit for True power (resistive power). VAR is the unit for how much
ampere. power is consumed by the reactive components. Volt-amperes is the combination
of the resistive and reactive powers.
What is meant by the term "locked rotor torque"? The torque that a motor develops when the rotor is at standstill and full power is
applied is called locked rotor torque.
What do we call the torque that a motor produces, when breakdown or pull out torque
operating at rated voltage and frequency, at the instance
an increase in load causes the motor to stall?
Explain the difference between dynamic and The difference between dynamic and regenerative braking is that regenerative
regenerative braking. braking systems remain connected to power to charge the circuit, while dynamic
braking has to dissipate that energy as heat.
Name at least two sources of the feedback signal. CEMF produced by the motor, tachometer-generator on the motor shaft
Explain the importance of the feedback signal. Why is it the feedback signal is needed to be compared to the control signal, the
needed? difference between the two is called the error signal.
What does the term "error signal" mean? error signal is the difference between the control and feedback signal
True or False? A higher percentage of regulation is better false
than a lower percentage of regulation.
What is meant by CEMF? cemf stands for counter electromotive force
Torque is best defined as ________________________________ rotational force
produced by a motor.
Describe the operation of a tachometer-generator. as the motor turns, the generator turns and produces a positive DC voltage
Is the voltage generated by a tachometer-generator proportional
proportional or inversely proportional to motor speed?
True or False? The summing point is that point in a circuit false
where the output from the sawtooth generator is joined
with the output form the preamplifier.
