Measurement and Instrumentation - Measurement of Mutual Inductance

Here are some methods and techniques for measuring mutual inductance:

Mutual Inductance Formula: The mutual inductance (M) between two coils can be calculated using the formula:

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M = (V2 * ∆I1) / (∆I2)

Where:

V2 is the voltage induced in the second coil

∆I1 is the change in current in the first coil

∆I2 is the change in current in the second coil

Bridge Method: The Maxwell's bridge or Hay's bridge is a popular method to measure mutual inductance. In this method, a bridge circuit is balanced by adjusting resistors and comparing the inductance to be measured with a known inductance.

Oscillator Method: This method involves connecting the two coils in an oscillator circuit. The mutual inductance can be calculated based on the frequency change of the oscillator when the coupling between the coils is changed.

Transformer Ratio Arm Method: This method uses a known transformer with a fixed ratio, and the mutual inductance is determined by comparing the voltage ratio of the test transformer with the known transformer.

Magnetic Linkage Method: This method uses a pair of coils wound on a common core. The voltage induced in the secondary coil is measured for a known change in current in the primary coil.

Inductive Voltage Divider: A known inductor is used as a voltage divider along with the inductor whose mutual inductance is to be measured. The ratio of the voltages across the two inductors can be used to calculate mutual inductance.

Inductive Mutual Impedance: By measuring the mutual impedance between two coils at different frequencies, the mutual inductance can be determined.

Impedance Bridge Method: This method uses an impedance bridge to measure the mutual inductance by comparing the impedances of the coils under test with that of a known reference coil.

It's important to note that measuring mutual inductance accurately can sometimes be challenging due to factors like stray capacitance, proximity effects, and non-ideal behavior of the components. Depending on the level of accuracy required and the specific characteristics of the coils being measured, different methods and techniques might be more suitable.