There are two basic classifications of relays:
One main difference between them is electromechanical relays have moving parts, whereas solid state relays have no moving parts.
Electromechanical Relays
Power relays are used for many different applications, including:
- Electromechanical Relays
- Solid State Relays
One main difference between them is electromechanical relays have moving parts, whereas solid state relays have no moving parts.
Electromechanical Relays
Electromechanical relays are switches that typically are used to control high power electrical devices. Electromechanical relays are used in many of today's electrical machines when it is vital to control a circuit, either with a low power signal or when multiple circuits must be controlled by one single signal.
Advantages of Electromechanical relays include lower cost, no heat sink is required, multiple poles are available, and they can switch AC or DC with equal ease.
Some of the electromechanincal relays are general purpose relays, power relay, contactor and time delay relay.
General Purpose Relay
Well known applications of general purpose relays are:
- Lighting controls,
- Time delay controls,
- Industrial machine controls,
- Energy management systems,
- Control panels,
- Forklifts,
- HVAC.
The general-purpose relay is rated by the amount of current its switch contacts can handle. Most versions of the general-purpose relay have one to eight poles and can be single or double throw.
General Purpose Relays are cost-effective 5.1-15.1 Ampere switching devices used in a wide variety of applications.
These are found in computers, copy machines, and other consumer electronic equipment and appliances.
Power Relay
Power relays are used for many different applications, including:- Automotive electronics
- Audio amplification
- Telephone systems
- Home appliances
- Vending machines
Power relays also contain a spring and an armature and one or many contacts. If the power relay is designed to normally be open (NO), when power is applied, the electromagnet attracts the armature, which is then pulled in the coil’s direction until it reaches a contact, therefore closing the circuit. If the relay is designed to be normally closed (NC), the electromagnetic coil pulls the armature away from the contact, therefore opening the circuit.
Power relay is used for switching a wide variety of currents for applications including everything from lighting control to industrial sensors.
The power relay is capable of handling larger power loads 10-45 amperes or more. They are usually single-pole or double-pole units.
