Share your understanding of how relays work. How do relays support small motors and solenoids? How can protective relays prevent equipment damage? Discuss some various types of relays and their functions. A relay is an electromechanical device consisting of a solenoid (coil and amateur) and one or more sets of contacts. Essentially, creating an electrically operated switch. This means a relay contains two distinct circuits. The control circuit that energizes and operates the relay, and the load circuit that is controlled by the relay. Relays have many different uses. They can be used to interlock functions electrically, a physical if/than interface if you will. They can be used as an isolation, isolating the control electronics from the power side in machinery. They can serve as a protective function to deenergize equipment during a fault condition. They can also allow relatively low voltage and low current control circuits to start and stop large electrical loads. Relays can be designed as Voltage relays (coil in parallel with load), Current relays (coil in series with load), or Time delay relays, where a contact is opened or closed after a specified time delay. A solenoid contains a coil, which is basically an inductor, so it will store some energy, but this will be dissipated shortly after the relay is de-energized. A relay can also be wired to be normally opened, or normally closed.