Chapter 12 Flashcards
One of the avantages of using a double-break contact instead of a single break contact is that a double-break contact _______.
has a higher contact rating in a smaller space.
________ power line(s) must be broken when using a contactor to control a 3 phase load.
three
_______ are uses to help confine, divide, and extinguish arcs for each set of contacts.
Arc chutes
The power rating of a contactor or motor starter_____as the NEMA number (size 1,2 etc..) of the contactor or motor starter increases.
increase
As ambient temperature increase, _____ current is needed to trip overload devices.
less
______ contactor assemblies are made of laminated steel.
AC
The current rating of a contactor or motor starter is the rating for ______.
each individual contact
Copper contact have been replace with _____ alloy contacts because of the problems of using copper with knife switches.
silver
A _____ diagram shows the connection and placement of an installation or its component devices or parts.
wiring
____________ interlock contactors are two contactors that are connected in such a way that both sets of contacts cannot be close at the same time
Mechanical
Manual starters are selected based on phasing, number of poles, voltage, starter size, and _________
enclosure type
A(n) _________ is a condition that occurs what a motor is loaded so heavily that cannot turn.
locked rotor
The three stages that a motor must go through in normal operation are resting, starting, and ___________.
operating under load
Fuses or________ are used to protect a motor against very high current, short circuit and, or a ground fault.
circuit breaker
A 120 V, 1 phase source has one hot wire and _______ natural wire(s)
one
A 230 V, 1 phase power source has two hot wires and _____ neutral wire(s)
no
A 3 phase power source has _____ hot wire(s) and zero neutral wires.
three
A _________ is a device that is used only periodically to remove electrical circuits from their supply source.
disconnect
Manual contactors are normally used with _____ circuit and resistance loads.
lighting
The main device in an overload relay is the _____.
eutectic alloy tube
A manual starter is a ___________ with an added overload protection divice.
contactor
Overload protection devices are required by the _________.
NEC - National Electrical Code
_________ temperature is the temperature of the air surrounding a motor.
Ambient
A _______ alloy is a metal that has a fixed temperature at which it changes directly from a solid to a liquid state.
eutectic
A starter may be reset after a _____ is removed.
overload
Enclosures provide _______and electrical protection for the operator and the starter
mechanical
An ___________is a control device that uses pushbuttons to energize the load connected to it.
manual contactor
________ contact are contact that brake electrical circuit in two places
double-banker
A(n) ____________ is a sensing device used to monitor the heat generated by excessive current and the heat created though ambient temperature rise.
heater coil
NEMA Type ___________ enclosures are intendant for indoor use primarily to provide a degree of protection from human contact with the enclosed equipment in locations where unusual service condition do not exist.
one
Manual motor starters are used in applications such as air compressors, conveyor systems, and _________.
drill presses
Manual contactors directly control _________circuits.
power
A(n) _____________ overload measures the strength of the the magnetic field around the wire instead of converting the current into heat.
electronic
__________ arcs are the most difficult arcs to extinguish on a set of contacts.
DC
The main difference between a contactor and a motor starter is the addition of ______ to the motor starter.
overload
Two overload relays used to protect motors are thermal and _______ overload relays.
magnetic
Ambient temperature, full-load current rating, and _________ must be know when selecting the overloads for a motor starter.
service factor
An inherent motor protector is designed to protect a motor from _______
overloading
__________ contactor assemblies may have several sets of contacts.
AC
A(n)________ is a device that dissipates the energy present across opening contacts.
arc suppressor
A(n) ___________ relay is an overload relay which resets automatically.
bimetallic
A(n) ___________ is built into an overload device to indicate to the operator that an overload has taken place within the device.
trip indicators
________ are used on large motor starter to reduce the current flowing to the overloads relay.
current transformer
_________ are overload devices located directly on or in a motor to provide overload protection.
Inherent motor protector
A(n) ____________ performs the same function as a motor starter, but can also vary motor speed, reverse the motor, and display operating information.
motor drive
A(n) ________ is an electronic device that changes AC into DC
converter
A(n) ________ is an electronic device that changes DC into AC
inverter
Article _________ of the NEC covers the design and installation of electronic system that contain motors, motor circuits,and motor controllers.
430
When motor was first introduced, they were started and stop by______.
knife switches
______ are used to provide a magnetic field that helps move contacts apart as quickly as possible.
Blow-out coils
