Depending upon supply lo and 3 ELCB are connected according to use
1) Current-operated ELCB is generally known as Residual-Current Devices (RCD).
2)These also protect against earth leakage. Both circuit conductors (supply and return) are run through a sensing coil: any imbalance of the currents means the magnetic field does not perfectly cancel. The device detects the imbalance and trips the contact.
3) When the term ELCB is used it usually means a voltage-operated device. Similar devices that are current operated are called residual current devices, However, some companies use the term ELCB to distinguish high sensitivity current operated 3 phase devices that trip in the milliamp range from traditional 3 phase ground fault ground fault devices that operate at much higher currents.
Typical RCB circuit:
The Supply Coil ,coil the neutral coil and the search coil all wound on a common transformer core.
On a healthy circuit the same current passes through the phase coil. the load and return back through the neutral coil. Both the phase and the neutral coils are wound in such a way that they will produce an opposing magnetic flux With the same current passing through both coils, the magnetic clock will cancel out under a heavy circuit condition
In a situation when there is fault a leakage to earth in the load circuit of where between the load circuit and the output connection of the RC circuit, the current running through the neutral coil has been reduced.
Then the magnetic flux inside the transformer core is not balanced any more. The total sum of the opposing magnetic flux is no longer an. This net remaining Flux is what we call a residual flux
The periodically changing residual flux inside the transformer core crosses path with the winding of the search coil. This action produces an electromotive force (emf) across the search coil An electromotive force is actually an alternating voltage.
The induced voltage across the search coil product a current inside the writing of the trip is this current that operates the trip coil of the circuit breaker. since the trip current is driven by the residual magnetic flux (the resulting flux, the net effect between both flux) between the phone and the neutral coil current device is called the residual
With a circuit breaker incorporated as part of the circuit the assembled system is called residual current breaker (RCCI) or residual current device (RCD) The incoming current is to pass through the circuit breaker first before going to the phase coil.
The return neutral path passes through the second circuit breaker pole During tripping when a fault is detected, both the phase and neutral connection is isolated.
RCD sensitivity is expressed as the need residual operating current, noted LAN. Preferred values have been defined by the IEC, thus making it possible to divide RDD into three groups according their LAN value
High sensitivity (C) 6-10-30 mA for direct contact life injury protection)
Standard IEC 60755 (General requirements for residual current operated protective devices) defines three types of RCD depending on the characteristics of the fault current.
