Basic electrician practice: identification and measurement of inductance
I. Basic concepts of inductance
Inductors, also known as inductive components, belong to energy storage components, which can convert electrical energy into magnetic energy and store it. Inductors mainly play the role of frequency division, filtering and resonance in circuits, and are mainly classified into the following categories according to their structure and use:
Figure 12-5 Symbols and Shapes of Inductors
II. Inductance Measurement Methods
(1) Measure the inductance coil on and off:Use a multimeter resistance block to directly test the coil for an open circuit.
(2) Dynamic feedback of measured inductance:When using a pointer multimeter, the initial judgment is made by observing the micro-movement feedback of the pointer through the momentary on-off.
(3) The inductance method calculates the inductance value:
Connect a resistor in series with an alternating current, measure the voltage across the inductor and the current through it, and calculate the inductive reactance XL from Ohm's law. then calculate the value of the inductance according to the following formula:
Style:
- X, - reactance in ohms (Ω).;
w - the angular frequency of the power supply in radians/second;
f - frequency in hertz (Hz).;
L-- Coil inductance, unit is Henry (H).
When measuring coils with high inductance values (e.g., large transformer windings), high voltage may be generated at the moment of disconnecting the measurement due to the inductance's reverse electromotive force characteristic. Be sure to pay attention to meter range protection and operational safety.
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