Chapters 4-6 DC/AC Drives

___ motors are commonly 1/20 HP or less because of the low starting torque.

**Shaded-pole** Split-phase Capacitor-start Capacitor-run

___ speed is the theoretical speed of a motor based on the number of poles of the motor and line frequency.

**Synchronous** Frequency Line Centrifugal

A(n) ___ shunt field is a shunt field connected to the same power supply as the armature.

**self-excited** repulsion separately excited induction

When motor starters are used to perform motor reversing, ____ starters are required.

2 (Page 108)

A typical dual-voltage, 3Φ motor rating is ___ V.

208/460 208/480 **230/460** 230/480

DC series motors can develop ______% of full-load torque upon starting.

500 (Page 110)

Capacitor motor

A 1Φ motor with a capacitor connected in series with the stator windings to produce phase displacement in the starting or running winding and add higher starting and/or running torque.

DC compound motor

A DC motor with the field connected in series and shunt with the armature.

Locked in step

A motor condition that occurs when the field of the stator and the field of the rotor are parallel to one another, not allowing the shaft to rotate.

inverter duty-rated motor

A motor made with wire and insulation that resist voltage spikes and high temperatures to extend the life expectancy of the motor.

AC drive motor

A motor specifically designed for use with an electric motor drive.

Induction motor

A motor that has no physical electrical connection to the rotor because there are no brushes.

Dual-voltage motor

A motor that operates at more than one voltage level.

Single-voltage motor

A motor that operates at only one voltage level.

direct current (DC) motor

A motor that uses direct current connected to the field and armature to produce shaft rotation

DC permanent-magnet motor

A motor that uses magnets, not a coil of wire, for the field winding.

DC series motor

A motor with the field connected in series with the armature.

DC shunt motor

A motor with the field connected in shunt (parallel) with the armature.

repulsion motor

A motor with the rotor connected to the power supply through brushes that ride on a commutator.

separately excited shunt field

A shunt field connected to a different power supply than the armature.

Self-excited shunt field

A shunt field connected to the same power supply as the armature.

Centrifugal switch

A switch that opens to disconnect the starting winding when the rotor reaches a preset speed and reconnects the starting winding when the speed falls below the preset value.

3. A capacitor start-run motor uses___ capacitor(s) for successful operation.

A. 0 B. 1 C. 2 (Page 102) D. 3

1. ____ speed is the theoretical speed of a motor based on the number of poles of the motor and line frequency.

A. Base B. Calculated C. Nameplate D. Synchronous (Page 94)

Combining a(n) _____ and an electric motor drive allows for maximum control and monitoring of a motor.

A. HIM B. manual motor starter C. PLC (Page 123) D. soft starter

5. Although any two lines can be interchanged to change the direction of rotation of a 3Φ motor, the industrial standard is to interchange ____ and ____.

A. T1; T2 B. T1; T3 (Page 107) C. T2; T3 D. X2; X3

2. The industrial standard for reversing a 1Φ motor is to reverse the _____ winding.

A. commutator B. run C. starting (Page 99) D. synchronous

Most ____ provide manual control functions for starting, stopping, jogging, reversing, speeding up, and slowing down directly from the keypad.

A. electric motor drives (Page 125) B. magnetic motor starters C. manual motor starters D. PLCs

4. When a dual-voltage, wye-connected, 3Φ motor is connected to high voltage, the individual coils of each phase will be in ____.

A. parallel B. series (Page 106) C. series-parallel D. shunt

Electric motor drives are either AC drives or DC drives, with ____ drives being the most common.

AC (Page 129)

split-phase motor

An AC motor that has running and starting windings.

shaded-pole motor

An AC motor that uses a shaded pole for starting.

Pigtail

An extended, flexible connection or a braided copper conductor.

Direct current

Current that flows in one direction only.

The ____ motor is used when high starting torque and constant speed are required.

DC compound (Page 112)

A rotor is the stationary part of an AC motor that produces a rotating magnetic field.

False

Shaded-pole motors produce high starting torque.

False

Typically, dual-voltage, 30 motors have 12 leads coming out of the motor box.

False (Page 107)

DC motors require less maintenance than AC motors.

False (Page 109)

The field is the part of the armature that connects each armature coil to the brushes by using copper bars that are insulated from each other with pieces of mica.

False (Page 109)

The wires extended from the series coil of a DC motor are marked A1 and A2.

False (Page 110)

The voltage of a control circuit is higher than the rating of the motor in most motor control circuits.

False (Page 127)

Reduced-voltage starting of large horsepower motors typically causes problems in power distribution systems.

False (Page 131)

Some electric motor drives allow control functions to be controlled through standard communication ports such as RS-202C ports.

False (Page 131)

Wye-delta motors are specially wound with nine leads extending from the motor to enable the windings to be connected in either a wye or delta configuration.

False (Page 136)

Typically, triacs are used as solid-state DC switches.

False (Page 137)

A shaded-pole motor is an AC motor that has running and starting windings.

False (Page 99)

Chapter 5 Electrical Motor Control

Jesus Christ... gonna be a long one.

The industrial standard to reverse 3Φ motors is to interchange ___.

L1 and T1 L2 and T2 L3 and T3 **T1 and T3**

____ are also known as holding or sealing circuits.

Memory Circuits (page 142)

___ starting is a motor starting method that uses resistors connected in the motor conductors to produce a voltage drop.

Primary resistor (Page 133)

____ starting is used to reduce the large current drawn from the power company when full-voltage starting is applied to large horsepower motors.

Reduced voltage (Page 131)

____ is the difference between the synchronous speed and the actual speed of a motor.

Slip (Page 95)

Slip

The difference between the synchronous speed and the actual speed of a motor.

line frequency

The number of complete electrical cycles per second of a power source.

commutator

The part of the armature that connects each armature coil to the brushes by using copper bars (segments) that are insulated from each other with pieces of mica.

Armature

The rotating part of a DC motor

Rotor

The rotating part of an AC motor.

Brush

The sliding contact that makes the connection between the rotating armature and the external circuit (power supply) to the DC motor

Stator

The stationary part of an AC motor that produces a rotating magnetic field.

field

The stationary windings, or magnets, of a DC motor.

Synchronous speed

The theoretical speed of a motor based on the number of poles of the motor and line frequency

A capacitor motor is similar in design to a split-phase motor.

True

The speed (rpm) of a DC motor is proportional to the voltage applied to the motor.

True

When connecting a dual-voltage motor, the higher voltage is usually preferred.

True

A DC shunt motor is a motor with the field connected in parallel with the armature.

True (Page 110)

A pigtail is an extended, flexible connection or braided copper conductor.

True (Page 110)

A separately excited shunt field is a shunt field connected to a different power supply than the armature.

True (Page 111)

Direct hard wiring is the most straightforward and oldest motor control method.

True (Page 123)

A locked rotor is the condition in which a motor is loaded so heavily that the motor shaft cannot turn.

True (Page 125)

Magnetic motor starters include high-power contacts for switching a motor ON and OFF and typically include auxiliary contacts that are used in the control circuit.

True (Page 126)

Placing contactors and soft starters in parallel allows for soft starting and soft stopping of motors without the need for large heat sinks during motor operation.

True (Page 128)

DC drives control speed by varying the amount of voltage and current on the field and armature of the motor.

True (Page 129)

Autotransformer starting is a motor starting method that uses a tapped 30 autotransformer to provide reduced-voltage starting.

True (Page 134)

Electric motor drives are programmed to apply a voltage boost at low motor speed to compensate for the power loss of a motor.

True (Page 139)

Fans and pumps are typically classified as variable torque/variable horsepower loads.

True (Page 139)

Typically, the control voltage used by electric motor drives is a low voltage, 24 VDC.

True (Page 141)

Analog input devices/signals connected to electric motor drives include potentiometers and variable voltage inputs.

True (Page 142)

Line frequency is the number of cycles per second of the supplied voltage.

True (Page 94)

Locked in step is a motor condition that occurs when the field of the stator and the field of the rotor are parallel to one another, not allowing the shaft to rotate.

True (Page 94)

A(n) ___ is the stationary part of an AC motor that produces a rotating magnetic field.

armature rotor **stator** endbell

A(n) ____ is the rotating part of a DC motor.

armature (Page 109)

A(n) ______ opens to disconnect the starting winding when the rotor reaches a preset speed.

centrifugal switch (Page 99)

The ___ is the stationary windings, or magnets, of a DC motor.

commutator **field** pigtail armature

A(n) ____ 3Φ motor has each phase wired end to end to form a completely closed loop circuit.

delta connected (Page 104)

A(n) ___ motor is a motor that has no physical electrical connection to the rotor because there are no brushes.

delta-connected **induction** repulsion wye-connected

A DC permanent-magnet motor uses magnets, not a coil of wire, for the ______.

field winding (page 112)

Soft starting is achieved by ___ a motor's voltage gradually in accordance with the setting of the ramp-up control.

increasing (Page 127)

A(n) _____ is a motor that has no physical electrical connection to the rotor because there are no brushes.

induction motor (Page 102)

When using the ____ method, motor speed is controlled from the keypad of the electric motor drive.

local control (Page 130)

A(n) ___- is a starter that has an electrically operated switch (contactor) and that includes motor overload protection.

magnetic motor starter (Page 126)

A(n) ____ circuit is a circuit that provides control functions such as starting, stopping, jogging, direction of rotation control, speed control, and motor protection.

motor control (Page 125)

When connecting a dual-voltage, delta-connected, 3Φ motor to low voltage, the individual coils of each phase are in _____

parallel (Page 106).

A DC ___ motor is used when high starting torque and constant speed are required.

series shunt **compound** permanent-magnet

Transistors, silicon-controlled rectifiers, triacs, and alternators are used as ____ switches.

solid state (Page 136)

A ___ motor leaves the starting winding and capacitor in the circuit at all times.

split-phase capacitor-start **capacitor-run** capacitor start-and-run

Chapter 4

starts here

The ____ applied to the stator of an AC motor must be decreased by the same amount as the frequency when controlling speed.

voltage (Page 138)