Common Electrical Symbols & Diagrams Flashcards
Auxiliary Contact
Light duty contacts in a motor starter that are in addition to the main motor contacts.
When the start coil is energized the ___ is actuated.
auxiliary contact
Auxiliary Contacts can be either normally open or normally closed. True or false?
True
Backfeed
Voltage present in a circuit that comes from the direction of the load.
Control Circuit, Motor
The circuit of a control apparatus or system that carries the electric signals directing the performance of the controller, but does not carry the main power current.
Downtime
The time equipment is not operating because of a breakage or failure.
Emergency Stop Switch
A safety device installed in the system, when activated, will immediately start the emergency stop sequence.
Fail Safe
A control circuit having adequate control and alarm devices to provide reliable protection of the system.
Flow Switch
A switch designed to measure and report the flow of a fluid or gas.
Holding Circuit
A circuit path that is parallel to a momentary start push-button.
Ladder Diagram
A schematic diagram resembling a ladder.
Level or Float Switch
A switch actuated by liquid level. A float or some other sensing device is located in the liquid.
Limit Switch
A switch that is operated by mechanical movement of some part of the machine or equipment to alter the associated electric circuit.
Magnetic Overload
An overcurrent device that breaks an electric circuit when operated by the electromagnetic force produced by excessive load current.
Maintained
A device that when actuated remains in that position.
Momentary
A device actuated by physical means and when released returns to its original position.
Sequence Chart
The operating steps in which a circuit works.
Normally Closed
A switch contact that is closed when no power or force is applied to the actuating mechanism.
Normally Open
A switch contact that is open when no power or force is applied to the actuating mechanism.
Potentiometer
A device used to vary voltage and/or current for control purposes by varying the resistance in the circuit.
Pilot Device
A manual or automatic switch used in a control circuit. It does not carry the main power current.
Pressure Switch
A switch actuated by steam, water, oil, gas, or some other pressure. It opens or closes on rise or fall of pressure.
Reference Designator
A control symbol designating an item such as a control relay.
Starter
A device that starts and stops a motor either manually or automatically and provides overload protection.
Schematic Diagram
Shows, by means of graphical symbols, the electrical connections and functions of a specific circuit without regard to the actual location of components.
Separable
Circuit connections which may be joined or connected by means of terminals or plug-in jacks.
Stop/Start Station
A pilot device with a normally open start switch and a normally closed stop switch.
Temperature Control
A switch actuated by rise or fall of the temperature of the medium it is controlling.
Thermal Overload
A device which breaks an electrical circuit when current flow is excessive by heating a tripping device.
Three-Wire Control
A basic control circuit using at least three wires to connect the pilot device to the starter.
Time Delay Switch
A switch actuated by an electrical timing device with contacts that will open or close after some predetermined delay.
Wiring Diagram
A pictorial layout drawing that shows component location and the routing of wires and terminal connections.
Pressure Control
A switch actuated by steam, water, air, oil or gas pressure.
Pilot Light
A visual annunciator to indicate power to a specific circuit; the function must be defined. The letter in the center indicates lens or lamp color.
American Standards Association (ASA)
Develops and documents standard electrical symbols.
