What are mechanical relays?
Mechanical relays consist of a coil (electromagnet) and contacts. The coil is activated when the proper voltage is applied and current is running through it. Once the coil is activated, it exerts a force on the common (COM) contact which moves it, connecting it with the normally open (NO) contact.
What are the 3 main parts of a relay?
Basic parts and functions of electromechanical relays include:
- Frame: Heavy-duty frame that contains and supports the parts of the relay.
- Coil: Wire is wound around a metal core.
- Armature: A relays moving part.
- Contacts: The conducting part of the switch that makes (closes) or breaks (opens) a circuit.
How are mechanical relays used in a circuit?
Mechanical relays are devices that can turn on or turn off the power supplied to another device, like a switch. However, instead of having a person flip the switch, mechanical relays switch when provided with a small amount of power. This allows high-power circuits to be controlled by low-power devices.
How often should you switch mains with a mechanical relay?
You should be careful when using mechanical relays in applications that require very frequent switching. Typically, mechanical relays can only manage one contact every few seconds- any quicker and they may begin to overheat. Two circuit diagrams showing the improper and proper ways of switching mains electricity with a relay.
What happens when a mechanical relay goes bad?
When an mechanical relay fails, it often fails permanently closed. This is because the contacts can actually weld to each other. See the section on Arcing, Interference, and Sticking for more information. This means that as long as the power supply remains on, the load will be powered, possibly creating a fire or safety hazard.
What do students need to know about relay logic?
Students need to be able to recognize these ladder logic sub-circuits at a glance, or else they will have difficulty analyzing more complex relay circuits that use them. Predict how the operation of this relay logic circuit will be affected as a result of the following faults.