Electrical Engineering ⇒ Topic : Advantages and Disadvantages Permanent Magnet Type

Advantages

• Uniform scale
• Since driving power is small, power consumption is low.
• Due to aluminium or copper former, hysteresis loss is absent.
• Very effective and reliable eddy current damping.
• Torque-weight ratio is very high.
• Due to application of intense polarized or unidirectional field, stray magnetic field has no effect.
• Using shunts or multipliers, ranges can be extended.

Disadvantages

• AC quantity cannot be measured.
• Compared to moving iron instruments, these instruments are costlier.
• Friction, temperature, ageing of control springs, and permanent magnets might introduce errors