Hello friends, today I am going to tell you Construction and Working of Non-directional Induction Type Overcurrent Relay: If you also want to know, then keep reading this article completely.
Construction and Working of Non-directional Induction Type Overcurrent Relay
This relay is also called earth leakage induction. Overcurrent relay operates when the current in the circuit exceeds a specific preset value. Induction type non-directional overcurrent relays can be constructed in the same way as a wattage meter with some modifications.
The construction details of a non-directional induction type over the current relay are shown in the figure.
It is made up of two electromagnets. Its upper end is shaped like the English letter ‘E’ while the lower end is shaped like ‘U.’ The aluminum disc rotates freely between two magnets.
The upper magnet has two windings – primary and secondary. Primary windings, CT of the line The windings are taped at intervals, which is to be secured.
This taping is connected to or connected to the plug setting bridge. Thus the required current setting for the relay is achieved. Generally, there are seven sections of taping, which are in the overcurrent range of 50 percent to 200% in step of 25 percent. These values are the percentage of the relay’s current rating. Thus a relay current rating will be 10A, i.e., CT with a secondary current rating of 10A. Will connect to.
But the operation can be started only at 50 percent setting of the relay 5A. Therefore a pin inserted between the spring-loaded jaws of the bridge socket to adjust the current setting would require an appropriate tape value. When a pin is removed to change the setting while the relay is in operation, the relay will automatically adopt the high current setting. Thus CT, There will be no secondary open circuit. Thus the relay will continue to operate even when a fault is being generated while changing the setting.
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The secondary winding on the central limb of the upper magnet is connected in series with the winding on the lower magnet. This winding receives energy from the primary through induction. By the arrangement of the secondary winding, the leakage fluxes of the upper and lower magnets will be adequately replaced in the space or space and time from which the rotating torque is generated on the aluminum disc. Control torque is achieved by a spiral spring.
When the current exceeds its preset value, the contacts and discs on the spindle rotate to make connections with the trip circuit terminals. The angle of rotation of the disc ranges from 0 to 360 degrees. The travel of the moving contacts is adjusted by adjusting the angle of rotation of the disc. This allows the relay to indicate the desired time setting, which a pointer indicates to a time setting dial. The diameter of the dial ranges from 0 to 1. It is not a direct operating time, but it gives a multiplier or multiplier, which is used with the time plug setting multiplier to get the actual operating time of the relay. The manufacturer provides the time plug setting multiplier curve.
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Working principle of induction type relay
The working principle of induction type relay is similar to that of induction type measuring instruments (ammeter, voltmeter, wattmeter or energizer, etc.). In a relay, the deflecting torque is produced due to the interaction between the vortex currents in the aluminum or copper disc and the flux of the alternating current magnets.
When they intersect the face, an electromotive force is induced in the disc—this inspired. The vortex induces currents in the disc.
Structure of Induction Type Relay
This type of relay consists of two electromagnets with two windings in the top electromagnet. There is a primary winding, and the current is connected to the transformer’s secondary and taped on it.
These tapping plug settings are attached to the bridge and are often arranged such that who can calibrate the plug setting for current to percentage values of current. The setting dial is calibrated from 0 to 1.
The current rating for overcurrent protection ranges from 50% to 200%. Whereas for land fault protection, the range of the stream varies from 10% to 70%. Any desired taping can be achieved with the help of plugs. Thus with the help of this arrangement, the secondary winding of the current transformer is never open. Thus the current transformer in the relay is also protected as well as the relay is at a high setting while changing the protection setting. The inductive overcurrent relay is shown in the figure below.
In this, the secondary winding is short-circuited and energized by induction from the primary winding. Displacement occurs in both the phase and space of the primary and secondary windings, and a deflecting torque is applied to the AC disc in response to the induced eddy current.
In this relay, as the value of current increases, the torque of the disc increases, and the operating time decreases. Hence its nature is inverse with the time it occurs. This type of relay is also called an overcurrent relay.
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