What are different types of relays?
There are different types of relays like:
- Electromagnetic Relays.
- Latching Relays.
- Electronic Relays.
- Non-Latching Relays.
- Reed Relays.
- High-Voltage Relays.
- Small Signal Relays.
- Time Delay Relays.
What are the types of protection relays?
Basic classification of protective relays includes:
- Electromagnetic Relays: Armature. Induction cup / induction disc.
- Static Relays: Analog input signals are processed by solid state devices.
- Digital / Numerical Relays: Uses programmable solid state devices based on digital signal processing.
What relays are used in substation?
Protection and Relays Used In Main Circuit Board at a Power Grid Substation
- High speed biased differential relay.
- Directional inverse time overcurrent and earth fault relays.
- Instantaneous voltage relay.
- Auxiliary relays.
- High speed tripping relays.
- Definite time delay relay.
- Trip circuit supervision relay.
Where are relays used?
Relays are used wherever it is necessary to control a high power or high voltage circuit with a low power circuit, especially when galvanic isolation is desirable.
Why a relay is used?
Relays are used to provide time delay functions. They are used to time the delay open and delay close of contacts. Relays are used to control high voltage circuits with the help of low voltage signals. Similarly they are used to control high current circuits with the help of low current signals.
What is a relay diagram?
Relays control one electrical circuit by opening and closing contacts in another circuit. As relay diagrams show, when a relay contact is normally open (NO), there is an open contact when the relay is not energized.
What is common on a relay?
The COM (Common) connection of a relay is the part of the relay that moves. When a relay is off, the COMMON is connected to the NC (Normally Closed). The NO (Normally Open) connection of the relay is not connected until the relay turns on. It is possible to use Two relays to create a Normally Closed condition.
What does 87a mean on a relay?
Understanding Relays, part 2: DIN numbers and different types of relay
| Terminal | Which Circuit? | Definition |
|---|---|---|
| 87 | High current (load) | Output to device, normally open, pulled closed when coil is energized |
| 87a | High current (load) | Output to other device, normally closed, pulled open when coil is energized |
What is the common wire in a relay?
This is the terminal where you connect the device that you want to power if you want the device to be on normally when the relay isn’t powered and off when the relay is powered. -COM- This is the common terminal of the relay. If the relay is powered and the switch is closed, COM and NO have continuity.
Does polarity matter in a relay?
Yes, polarity in a DC relay will determine the magnetic field direction – but remember the solenoid / magnet is acting on a lump of iron. Not usually a magnet. So in general polarity is irrelevant.
Is normally open positive or negative?
4 pin (normally open) relay with the switch on the positive side of the control circuit. Example 2. 4 pin (normally open) relay with the switch on the negative side of the control circuit.