Maximizing Driving Torque in an Induction Type Instrument

In an induction type instrument, the driving torque is produced by the interaction between the magnetic field produced by the shunt coil and the magnetic field produced by the series coil. To maximize the driving torque, it is important to consider the phase relationship between these two magnetic fields.

Importance of Phase Relationship

The phase relationship between the flux produced by the shunt coil and the series coil determines the direction and magnitude of the driving torque. This phase relationship can be classified into four possibilities: in phase, quadrature, displaced by, and out of phase.

In Phase (Option A)

If the flux produced by the shunt coil and the series coil are in phase with each other, it means that the two coils generate their magnetic fields at the same time and in the same direction. In this case, the resulting driving torque will be zero because the magnetic fields cancel each other out. Therefore, option A is not the correct answer.

In Quadrature (Option B)

When the flux produced by the shunt coil and the series coil are in quadrature with each other, it means that the two coils generate their magnetic fields 90 degrees out of phase. This phase relationship results in a maximum driving torque because the magnetic fields reinforce each other. Therefore, option B is the correct answer.

Displaced By (Option C)

If the flux produced by the shunt coil and the series coil are displaced by with respect to each other, it means that the two coils generate their magnetic fields with a phase shift that is not 90 degrees. This phase relationship will result in a reduced driving torque compared to when the fluxes are in quadrature. Therefore, option C is not the correct answer.

Out of Phase (Option D)

When the flux produced by the shunt coil and the series coil are out of phase with respect to each other, it means that the two coils generate their magnetic fields with a phase difference greater than 90 degrees. This phase relationship will result in a driving torque, but it will be smaller compared to when the fluxes are in quadrature. Therefore, option D is not the correct answer.

Conclusion

To maximize the driving torque in an induction type instrument, the flux produced by the shunt coil and the series coil should be in quadrature with each other. This phase relationship ensures that the magnetic fields generated by the two coils reinforce each other, resulting in a maximum driving torque.