Explain MHO relay in detail.
MHO Relay: In this relay, poles 1, 2, 3 are energized by a voltage V through polarizing coil to produce flux, the capacitor connected provides phase shift. The left pole 4 is energized by a current which is the operating quantity. Here the rotor is hollow cylindrical type which turns around its axis. Inside the rotor stationary core is there. The rotating field is produced by operating coil flux and polarized flux. This rotating field induces currents in the cup to provide necessary driving torque, which closes the trip contacts of CB. The relay operation depends upon polarized flux because of voltage and operating flux because of current hence on the ratio (I/V) = Y i.e. admittance, hence called as MHO relay.