Some of the simplest and most effective methods of checking coils

Check coil pulse

Normally, the wires in the coil are insulated with a specialized coating, but over time, the insulation resistance can decrease, causing a short circuit. 

The pulse testing technique works by applying a pulsed voltage to the coil, then recording the response waveform. This waveform will be compared with a sample waveform from a well-functioning motor to detect any errors or damage. In this way, it is possible to determine the condition of the coil and draw more accurate conclusions

Changes in the coil's response waveform are determined by three main factors: the inductance value (L), the resistance value (R) of the coil, and the capacitance value (C) of the motor. Judgment method through area comparison is a commonly used way to measure the difference between the waveforms of normal and defective parts. 

Some modern devices also have the ability to automatically quantify this response waveform. The inductance, resistance and capacitance values ​​of the coil play an important role in calculating and evaluating waveform changes, helping to accurately determine the condition of the motor.

Measure insulation resistance

Insulation resistance measurement evaluates the insulation condition of the windings, especially useful in testing motor windings. When the insulation of the coil is degraded, the risk of electric shock or short circuit increases significantly. 

Checking the insulation condition of the coil is essential to ensure equipment safety. If the measurement results show that the resistance of the coil reaches infinity, it can be concluded that the insulation is still guaranteed.

Conversely, if the resistance is 0 Ω, this indicates that the insulation has been compromised and is likely to cause a problem. To achieve more accurate results, you should use a device with a contact test function, which makes it easier to check for damaged wires, avoiding erroneous conclusions during the test.

Reference: Hioki ST5520 insulation resistance tester

Ability to withstand testing

As well as measuring insulation resistance, withstand voltage testing is an important test method to ensure the coil is capable of withstanding the operating voltage without insulation problems. Sometimes, we can confuse these two techniques because they both aim to ensure safety, prevent electric shock and fire. However, each technique has a different approach and purpose.

Insulation resistance testing focuses on measuring resistance values ​​to detect defects in insulation. Withstanding voltage testing goes further, using a specific voltage level, usually determined by the product's safety standards, to test whether a failure occurs when the coil is subjected to high voltage or not. From there, we can evaluate the resistance of the insulation and ensure that the device will not have problems when operating in practice.

Measure the inductor

Inductance represents the ability to create an induced electromotive force when the current changes. It can be simply understood that it is like a resistance to alternating current. Coils designed to produce inductance are often called inductors, and they come in many different types. Some coils do not use a magnetic core, but only air or non-magnetic materials. Meanwhile, other coils have cores made from magnetic materials such as ferrite, which makes their inductance depend on the current flowing through them.

Inductors with magnetic cores also have the phenomenon of self-resonance, when the inductance and parasitic capacitance of the core create a resonant frequency, called the self-resonant frequency. To accurately measure the inductance of the coil, specialized measuring equipment such as an LCR meter should be used. However, it is important that the L and Q measurements be made at a frequency low enough relative to the self-resonance frequency to ensure the highest accuracy.

Coil inspection cannot be overlooked in electronic circuits, especially when checking product quality or during equipment maintenance and repair.

Product reference: HIOKI IM3536 LCR meter

Conclude:

Above are common methods to effectively check coils. If you find it useful, please follow EMIN Fanpage to update more information!