Ch25-33

If the motor nameplate indicates only the delta-comnected full load current, divide this value by___to obtain winding current

1.73

The slip at rated load may vary from 3 percent to ? for different types of motors

20%

The thermal capacity of the motor limits the length of acceleration on the first winding to approximately___seconds depending on the connected load

5

When full-voltage starting may cause serious line disturbances, reduced voltage starters may recommended for motors with ratings as small as

5 horsepower

Closed transition connections are usually found standard size ___and larger starters.

6

In an autotransformer-type starter, autotransformers supply___ of the line voltage to the motor.

65%

rotor winding consists of many copper or ? Bars into slots on rotor

Aluminum

correct rotational direction is indicated by___ on the driven machine

Arrows

The squirrel cage induction motor is a

Constant speed motor

In a two speed, reversing controller, an overload in either the low or high speed setting will de-energize the ___

Control circuit

Part winding starters are not suitable for use with delta-wound, ____motors

Dual voltage

Every function in solid-state starting units is illuminated with electronic LEDs.

False

In an automatic speed control for a two-speed, two-winding three-phase motor, the circuit is so designed that a certain amount of speed must be achieved before the motor can be changed from low to high speed

False

In an autotransformer-type starter the timing for the time-delay relay that controls the transfer from the reduced voltage

False

Locked rotor currents for different motor types vary from 10 to 20 times the full-load current of the motor.

False

Machines will not be harmed if the direction rotation is changed from that for which they are designed

False

Most motors are successfully started at 90% percent voltage.

False

Part winding motor windings intended operate in series.

False

Part winding motors are different in construction from standard squirrel cage motors.

False

Slip refers to the twisting or turning of the motor shaft.

False

Slow and continued speed transfers may activate the overload relays

False

Star-delta motor starting is sometimes called double-delta starting.

False

The energy- saving option, including a microcomputer, is activated before the motor is up to speed.

False

Three-speed, consequent pole have three windings.

False

With a compelling relay, the motor is started at low speed and is then accelerated automatically through successive speed steps until the seleted speed is reached

False

In addition to the greater noise immunity provided by integrated electronic circuits, the logic functions include additional

Filtering and buffering

The speed of a star-delta, squirel cage induction motor depends on the number of poles of the motor and supply line___

Frequency

Some starters have ___ compression disk resistors and are used for starting polyphase squirrel cage motora

Graphite

When selecting heater elements for the overload relays, the electrician should remember that each of the relays carries only ____of the motor current

Half

One disadvantage the two-step part winding starter is that

It is almost always an incremental start device

Solid-state provides a method for electrically controlling machines and different processes with _____elements and accessories

Logic

Star-delta motors are widely used on loads having high inertia and a___

Long acceleration period

The phrase pairs of poles is used to indicate that____poles are always in pairs

Motor

With primary resistor starters, the motor starts at a ___power factor than with other starting methods.

Much higher

Starting transformers momentarily affect the

Power factor

The inactive winding must be open circuited to ____circulating current due to transformer action between the idle winding and the energized winding

Prevent

Circuits for controlling a two speed consequent pole motor may use contactors with three load contacts because they are

Readily availabe

Four-speed consequent pole motors have two ____windings

Reconnectable

The most common function of reduced voltage starting devices is to_____the starting current

Reduce

The operating principle on which the squirrel cage motor is based calls for a rotor

Revolving with a stator

The fewer the number of poles established in the stator, the greater is the speed in ____ of the rotor

Rpm

A solid-state, reduced voltage motor starter uses___controlled rectifiers for power control

Silicon

Current transformers are used on large motor starters to step down the current so that a conventional overload relay and heater_____ may be used

Size

In the color coding LEDs , AMBER indicates -

Starting

Wye-delta starting is accomplished by connecting ___ in wye during the starting period and then reconnecting them in delta for normal run operation

Stator windings

Using the formula for speed, the___speed of a two-pole motor supplied by 60-hertz electrical energy is determined

Synchronous

When the starter is equipped with an accelerating relay

The final speed is determined by the button pressed

when a compelling relay is used

The motor must be started at low speed before a higher speed can be selected

In a standard starter, before change is made from a higher to a lower speed,

The stop button must be pressed

A thee phase squirel cage motor can be wound so that six leads are brought out.

True

By reducing the starting voltage, at the motor terminals, the starting torque is decreased.

True

Closed transition starting accomplished by adding another three pole contactor and resistors to the circuit

True

Compeling relays ensure that the motor starts at the lowest speed

True

De-energizing the transformers while in the running position is done to conserve electrical energy

True

Electromechanical devices are used provide interlocking methods and sequencing control.

True

Four speed, consequent pole, squirrel cage motors have two reconnectable windings and two speeds for each winding.

True

In a two speed, reversing controller, the circuit may provide automatic acceleration to high speed in either the forward or reverse direction

True

Magnetic overload relays are used on large reduced voltage starters.

True

Multispeed starters are provided with mechanical and electrical interlocking

True

Part winding starters are designed to be used with squirrel cage motors having two separate and parallel stator windings

True

Part winding starters can be used in many applications as other, more expensive types of reduced voltage starters.

True

Power-saving modules are available that detect idling or low-power periods of operation.

True

Primary resistor starters provide closed transition starting

True

Solid-state starters are available in ranges up to several hundred horsepower

True

Star delta motor are similar in construction to stand squirrel cage motors

True

Star-delta motors may be used where a reduced starting current is required.

True

Two-speed, consequent pole motors have one reconnectable winding

True

With impedance starting, reactors are used in series with the motor

True

primary resistance-type starter has a high power factor

True

primary resistance-type starter has a low initial cost.

True

In the part winding motor, the stator windings may be ____connected or delta connected, depending on the motor design

Y

With full-voltage starting:

b. a hand-operated or automatic starting switch throws the motor directly across the the line

Mechanical and electrical interlocking avoid the possibility of

connecting more than one speed winding at the same time

Starting compensators using a five-pole starting contactor are classified as

open transition starters

With part winding starting:

the stator windings of the motor are made up of two or more circuits

Primary resistor starters are used to start squirrel cage motors in situations where limited torque is required

to prevent damage to driven machinery

Primary resistor starters are used with limited current inrush

to prevent excessive power line disturbances

The design of the motor will determine the percentage of slip.

True

The squirrel cage induction motor is the most widely used industrial motor.

True

The starting transformers are inductive loads.

True

The use of an automatic starter and a control station gives greater operating efficiency.

True

Part winding starting has many applications in air-conditioning systems.

true

With an accelerating relay, the motor can be started only by pressing the low-speed push button.

False

With primary resistor-type starters, a resistor is connected in parallel in the lines of the motor

False

disadvantage of open transition starting is that it does not require accessory voltage reducing equipment.

False

primary resistor starters are available only with multi-points of acceleration.

False

Solid-state starters are an efecive choice in__applications.

Reduced voltage