Measurement of self-inductance is a fundamental aspect of electrical engineering and is crucial for understanding and designing circuits involving inductors. Self-inductance is a property of a circuit component (usually an inductor) that represents its ability to oppose changes in the current flowing through it. The unit of self-inductance is the henry (H).
Here are the basic methods for measuring self-inductance:
Bridge Method:
One common method for measuring self-inductance is the bridge method, which uses a Wheatstone bridge configuration. In this method, the inductor whose self-inductance is to be measured is connected in one arm of the bridge. By adjusting the resistors in the other arms of the bridge, a balance condition is achieved, and the self-inductance can be calculated using the bridge equation.
RL Time Constant Method:
This method involves connecting the inductor in series with a known resistance (R) to form an RL circuit. A step voltage is applied to the circuit, and the time constant of the resulting exponential rise in current is measured. By knowing the resistance and the time constant, the self-inductance can be calculated using the formula L = R * Ď.
Oscillator and Lissajous Figure Method:
In this method, an oscillator circuit that includes the inductor and a capacitor is used. The frequency of the oscillator is adjusted until a Lissajous figure (a graphical representation of the phase relationship between two oscillating signals) is formed on an oscilloscope. The self-inductance can be calculated using the formula L = (1 / (4Ď²f²C)), where f is the frequency and C is the capacitance.
RLC Resonance Method:
Another method involves creating a series RLC circuit (resistor, inductor, and capacitor) and sweeping the frequency of an AC source. When the circuit reaches resonance, the impedance of the circuit becomes purely resistive, and the resonant frequency can be used to calculate the self-inductance.
Mutual Inductance Compensation Method:
In this method, two coils are used â one with a known self-inductance and another with the inductor whose self-inductance is to be measured. By adjusting the currents through the coils and measuring the resulting voltages, the self-inductance can be calculated based on the known mutual inductance between the coils.
Remember that accuracy is crucial in these measurements, and factors like stray capacitance, resistance, and mutual inductance can introduce errors. Depending on the available equipment and the desired accuracy, the appropriate method can be chosen. Always make sure to follow proper safety procedures when working with electrical circuits and equipment.