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What is the definition of circuit breaker?

A safety device that detects too much current in a circuit. A circuit breaker often contains a bimetallic strip that bends and trips a switch that opens a circuit.
Learn more about circuit breaker in the class "Symbols and Diagrams for Motors 210" below.

Symbols and Diagrams for Motors 210

Motor Controls Training

Class Information

ToolingU.com classes are offered at the beginner, intermediate, and advanced levels. The typical class consists of 12 to 25 lessons and typically requires at least two hours of instruction time.

Class Name:	Symbols and Diagrams for Motors 210
Description:	This class describes common types of motor control symbols found in most schematic diagrams as well as their function in a motor application.
Prerequisites:	550255
Difficulty:	Intermediate
Number of Lessons:	16
Language:	English, Spanish

Below are all the competencies and job programs that contain the class Symbols and Diagrams for Motors 210. Job programs are our traditional class lists organized according to common job functions. Competencies are our latest job-specific curricula that help tie online learning to practical, hands-on tasks.

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Competencies
Maintenance Electrician

Class Outline
Objectives The Purpose of Motor Symbols and Diagrams Types of Motor Diagrams Contact Symbols Timed Contact Symbols Supplementary Contact Symbols Pushbutton Symbols Selector Switch Symbols Switch Symbols Types of Switch Symbols Coil Symbols Overload Relay Symbols DC Motor Symbols AC Motor Symbols Miscellaneous Motor Symbols Summary

Class Objectives

Describe the purpose of motor symbols and diagrams.
Identify the different types of motor diagrams.
Identify normally open and normally closed contacts.
Identify timed contact symbols.
Identify supplementary contact symbols.
Identify pushbutton symbols.
Identify selector switch symbols.
Identify types of switch symbols.
Identify types of switches.
Identify coil symbols.
Identify overload relay symbols.
Identify DC motor symbols.
Identify AC motor symbols.
Identify miscellaneous motor symbols.

Class Vocabulary
air flow switch		A type of flow switch that detects the movement of air. The air flow switch symbol has a flag shape that represents a sail.
alternating current		Current that regularly reverses the direction of its flow in a repeating, cyclical pattern.
armature		The part of a motor in which a current is induced by a magnetic field. The armature usually consists of a series of coils or groups of insulated conductors surrounding a core of iron.
bimetal strip		A strip made by bonding together two unlike metals that expand at different rates when heated.
bumper arm		A physical device on a limit switch that makes contact with an object causing the contact of the switch to change position.
circuit breaker		A safety device that detects too much current in a circuit. A circuit breaker often contains a bimetallic strip that bends and trips a switch that opens a circuit.
coil		A wound spiral of two or more turns of wire used to conduct current.
compound motor		A DC motor that uses both series and shunt field windings. Compound motors combine the advantages of the shunt and series motors.
constant speed motor		A type of motor that maintains a steady rate of rpm from no load to full load. DC shunt motors are often referred to as constant speed motors because they have this characteristic.
contact		A conductive part in an electrical circuit attached to a switch that opens or closes a circuit by coming in contact with or separating from the main conductor.
contactor		A device that uses a small control current to energize or de-energize a load.
control transformer		A type of transformer used to decrease the voltage to the value required by the motor control system.
diaphragm-operated switch		A type of pressure switch that senses small pressure changes at low pressures.
direct current		Current that flows in one direction. Direct current does not reverse the direction of flow.
electric motor		A machine that converts electricity into mechanical energy or motion. An electric motor is a common power source for a mechanical system.
electromagnetic starter		A device that has a magnetic coil that sends enough voltage to start a motor.
float switch		A type of switch that controls the action of a pump as it relates to the level of liquid in a tank. The float switch symbol has a circle connected to a line that represents a ball float.
flow switch		A type of switch that detects the movement of air or liquid in a duct or pipe. The flow switch symbol has a flag or paddle shape that represents either an air flow switch or a liquid flow switch.
fuse		A safety device that detects excess current in a circuit. Fuses often have a component that melts and opens the circuit.
ladder diagram		Another name for a line diagram, due to its resemblance to a ladder. In this sense, each circuit line is a "rung" of the ladder.
limit switch		A type of switch that detects the presence or absence of an object. The limit switch symbol has a wedge that represents the bumper arm.
line diagram		A diagram that shows the logic of an electrical circuit or system using standard symbols. Also known as a ladder diagram.
liquid flow switch		A type of flow switch that detects the movement of liquid. The liquid flow switch symbol has a flag shape that represents a paddle.
logic		The reasoning behind the functioning of something. Circuit logic comprises all the principles required to understand electrical circuitry.
magnetic relay		A type of overload relay that senses the strength of the magnetic field that the current flow produces. Magnetic relays are often used in areas that experience extreme changes in temperature.
maintained contact device		A type of device in which the switch or button physically keeps the circuit in the actuated position. An example of a maintained contact device is a light switch.
momentary contact device		A type of device in which the switch or button closes or opens the circuit only when it is actuated.
mushroom head		A type of pushbutton that is shaped like a mushroom.
National Electrical Manufacturers Association		An organization that defines a product, process, or procedure with reference to safety, performance, and testing. NEMA provides commonly used electrical symbol standards.
normally closed contact		An electrical contact that regularly allows electricity to flow. An NC contact has parallel lines with a diagonal line crossing them showing a closed connection.
normally closed held open		A type of switch that is connected normally closed but the contacts are held open when the circuit is de-energized.
normally open contact		An electrical contact that rarely allows electricity to flow. An NO contact symbol has parallel lines showing an open connection.
normally open held closed		A type of switch that is connected normally open but the contacts are held closed when the circuit is de-energized.
off-delay timer		A type of timer in which the contacts change position immediately when the coil is energized, but delay returning to their normal position when the coil is de-energized.
on-delay timer		A type of timer in which the contacts delay changing position when the coil is energized, but change back to their normal position immediately when the coil is de-energized.
output device		A device that performs a mechanical action after receiving the electrical signal to do so.
overload relay		A device that protects a motor from overheating due to an overload condition in the machinery.
pictorial diagram		A type of electrical print that shows the external appearance of each component in the circuit. A pictorial diagram is much like a photograph of the circuit.
pilot light		A type of indicator light found on machines.
pole		A set of moveable contacts that belong to a single circuit.
pressure switch		A type of switch that senses the pressure in a pneumatic or hydraulic system. The pressure switch symbol has a semi-circle connected to a line that represents the diaphragm.
prime mover		The device in a power transmission system that introduces energy into the system and converts the energy into the appropriate form.
pushbutton		A manual control device that opens or closes a circuit when pressed. Pushbuttons can be normally open or normally closed.
relay		An electrically controlled mechanical device that controls one circuit by opening and closing the contacts in another circuit.
schematic diagram		An electrical print in which all electrical components are represented with a symbol. Schematic diagrams show the electrical relationship of all components, but not the physical relationship of the components.
selector switch		A type of switch that can be turned to different positions to make a connection with the contacts in that particular position.
series motor		A method of connecting field windings in series with the armature. A DC series motor provides very high start-up torque but must never be run without a load.
shunt field		A winding of small wire and many turns designed to be connected in parallel with the armature of a DC motor or generator.
shunt motor		A method of connecting field windings in parallel with the armature. The shunt DC motor is commonly used because of its excellent speed regulation.
sine wave		The most common type of AC waveform. A sine wave consists of 360 electrical degrees and is produced by rotating machines.
single-phase motor		A type of AC motor that operates on either 120 or 240 volts and is used for most simple residential applications like furnaces, washing machines, and air conditioners.
solenoid		A coil of wire that converts electrical energy into linear motion.
squirrel cage rotor		A type of three-phase AC motor whose rotor is constructed by connecting metal bars together at each end. It is the most common AC motor type.
switch		A device that opens and closes a circuit.
symbol		Something that is used to signify something else. A schematic symbol represents an electrical component in a diagram.
temperature switch		A type of switch that detects the expansion of a metal. The temperature switch symbol represents a bimetal strip.
thermal relay		A type of overload relay that connects a heater with a motor.
three-phase motor		A motor with a continuous series of three overlapping AC cycles offset by 120 degrees. Three-phase power is used for all large AC motors and is the standard power supply that enters homes and factories.
throw		The number of stationary contacts that match the moveable contacts.
timing relay		A type of relay that delays changing position when the coil is energized or de-energized.
torque		A force that produces rotation.
wiring diagram		The most detailed of electrical prints. A wiring diagram shows the physical relationship of all the components, as well as the information needed to wire the circuit.
wobble stick		A type of lever used to actuate contacts on a pushbutton or switch unit.
wound rotor		A three-phase motor containing a rotor with windings and slip rings. This motor type permits control of rotor current by connecting external resistance in series with the rotor windings.