- Instantaneous Relay Definition: An instantaneous relay is defined as a relay that operates with no intentional delay when the current exceeds a set threshold.
- No Intentional Delay: Instantaneous relays activate without any added delay, making them very fast in operation.
- Inherent Delays: These relays still have minor delays due to electrical and mechanical factors, but they are not intentionally introduced.
- Types of Instantaneous Relays: Examples include attracted armature relays, solenoid type relays, and balance beam relays.
- Operation Mechanism: These relays rely on electromagnetic attraction to move a plunger or beam to close the relay contacts quickly.
In a simple example of an electrical relay, the fixed coil is connected to the circuit needing protection. When the current in the fixed coil exceeds the pick-up value, an iron plunger is attracted and moves up to close the normally open (NO) contacts. This relay operates very quickly. The NO contacts close immediately when the current surpasses the pick-up level, illustrating an instantaneous relay where there is ideally no delay between the current crossing the threshold and the contacts closing.
Definition of Instantaneous Relay
An instantaneous relay is defined as a relay with no intentional time delay. Ideally, it operates immediately when the current exceeds a certain level, though some unavoidable delays may still occur.
Since the current coil is an inductor, it takes a bit of time to reach its maximum value. Additionally, the mechanical movement of the plunger adds some delay. These inherent delays exist, but no extra time delay is intentionally added. Instantaneous relays can still operate in less than 0.1 seconds.
Examples of Instantaneous Relays
Several types of relays can be considered instantaneous relays. One example is the attracted armature relay, where an electromagnet attracts an iron plunger to actuate the relay. When the electromagnetic force exceeds the pick-up level, the plunger moves toward the magnet and closes the relay contacts. The electromagnet’s strength depends on the current flowing through the coil.
Another common type of instantaneous relay is the solenoid relay. When the current in the solenoid exceeds the pick-up value, it attracts an iron plunger, which then moves to close the relay contacts.
Balance beam relay is also an well known example of instantaneous relay. Here balance of one horizontally placed beam is disturbed due to pick up current in the relay coil. Due to unequal torques at two ends of the beam, it starts rotating against the hinge and ultimately closes the contacts of the relay.
