• The torque produced in induction type relay (shaded pole structure) is proportional to the square of the current.
• In an induction-type relay with a shaded pole structure, the operating principle is based on the interaction of a magnetic field produced by the energized coil and a shaded pole on the iron core.
• The shading coil creates a phase shift in the magnetic field, which produces a rotating magnetic field.
• The strength of this rotating magnetic field is proportional to the square of the current in the energized coil.
• The rotating magnetic field interacts with the metal disc or rotor, creating a torque that moves the rotor to operate the relay contacts.
• The torque produced is also proportional to the square of the current in the energized coil.

This can be expressed mathematically as:

T ∝ KI²

where

T is the torque produced

K is a constant of proportionality

I is the current in the relay.