What is a current relay in HVAC?
The purpose of a current relay is to either remove the start winding or a starting capacitor in series with the start winding from the circuit at startup. It can either be pushed onto the run and start pins of the compressor terminal or remotely mounted away from the compressor.
What operates a current relay?
A relay is an electrically operated switch. Current flowing through the coil of the relay creates a magnetic field which attracts a lever and changes the switch contacts.
What is a current start relay?
Current starting relays are used on single-phase, fractional horsepower motors requiring low starting torque. Their main function is to assist in starting the motor. Current starting relays consist of a low resistance coil and a set of normally open contacts.
Is a current relay normally open or closed?
Relays are switches that open and close circuits electromechanically or electronically. 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 are the 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 happens when a relay is energized?
When a relays coil is energized, current flow through the coil creates a magnetic field. Whether in a DC unit where the polarity is fixed, or in an AC unit where the polarity changes 120 times per second, the basic function remains the same: the magnetic coil attracts a ferrous plate, which is part of the armature.
What is the purpose of starting relays?
A starter relay acts as an electrical circuit completer or circuit breaker in between the vehicle’s battery and the starter motor. It helps to boost the battery’s current so that not as great a current is required at ignition. The starter relay is sometimes, but not always, used in addition to a starter solenoid.
What is a time over current relay?
Definite Time Over Current Relay. This relay is created by applying intentional time delay after crossing pick up the value of the current. A definite time overcurrent relay can be adjusted to issue a trip output at an exact amount of time after it picks up. Thus, it has a time setting adjustment and pickup adjustment.
What is setting over current relay?
Setting overcurrent relays involves selecting the parameters that define the required time/current characteristic of both the time-delay and instantaneous units. This process has to be carried out twice, once for the phase relays and then repeated for the earth-fault relays.
What is current start relay?
Current starting relays consist of a low resistance coil and a set of normally open contacts. The coil is wired between terminals L and M. The contacts are wired between terminals L and 2 when a start capacitor is used.
What is over current relays?
Over-current relays can be used to protect practically any power system elements , i.e. transmission lines, transformers, generators, or motors. For feeder protection, there would be more than one over-current relay to protect different sections of the feeder.