Chapter 4 Electrical Symbols and Diagrams Language of

Chapter 4 Electrical Symbols and Diagrams Language of Control • Pictorial Drawings • Electrical Symbols and Abbreviations • Wiring Diagrams • Schematic Diagrams • Electrical Circuits • Manual Control Circuits • Automatic Control Circuits • Magnetic Control Circuits • Printreading

A pictorial drawing shows the physical details of components as seen by the eye.

Symbols are used to conveniently represent electrical components in diagrams of most electrical and electronic circuits.

In a wiring diagram, the location of components is generally shown as close to the actual circuit configuration as possible.

In a schematic diagram, components are laid out so the circuit is easily read rather than to show the actual position of the components.

A line (ladder) diagram consists of a series of symbols interconnected by lines that are laid out like rungs on a ladder to indicate the flow of current through the various components of a circuit.

A one-line diagram is a diagram that uses single lines and graphic symbols to indicate the path and components of an electrical circuit.

Care should be taken when using electrical symbols to design or communicate electrical circuit operations because electrical circuit operations may be changed.

All electrical circuits include the source, load, control device, and conductors. Most circuits also include fuses or circuit breakers to provide protection to the circuit.

A line diagram may be used to illustrate a manual control circuit of a pushbutton controlling a pilot light.

A line diagram may be used to illustrate the control and protection of a 1 f motor using a manual starter with overload protection.

An electric motor on a sump pump can be turned ON and OFF by using an automatic control device such as a float switch.

The NC contacts of a float switch may be used for a pump operation to maintain a certain level of water in a livestock water tank.

A solenoid is an electric output device that converts electrical energy into a linear mechanical force.

A solenoid may be used to control a door lock that is opened only when a pushbutton is pressed.

A contactor is a control device that uses a small control current to energize or de-energize the load connected to it.

The electrical operation of a contactor can be shown using a line diagram, a pictorial drawing, and/or a wiring diagram.

Auxiliary contacts may be added to a contactor to form an electrical holding circuit.

A magnetic motor starter is an electrically operated switch (contactor) that includes motor overload protection.

The electrical operation of a motor starter can be shown using a line diagram, a pictorial drawing, and/or a wiring diagram.

Printreading requires understanding the relationship between a component symbol and the physical shape and location of the component.

Troubleshooting requires reading a print to determine the location and use of individual components and understanding how to use test equipment.