How to quickly determine whether a Flying Shear Motor has a winding failure?

1. Appearance inspection
1. Burning marks
Carefully observe the winding part of the motor to check if there are obvious signs of burning or discoloration. If the insulating paint of the winding is burnt and blackened, it is likely that the winding has a short circuit failure. Because when the winding is short-circuited, the current is too large, which will generate too much heat and burn the insulating paint.
This burning phenomenon may occur on the stator winding or rotor winding. Pay special attention to the end of the winding, which is a part prone to failure.
2. Insulation damage
Check whether the insulation layer of the winding is damaged or cracked. You can use auxiliary tools such as a flashlight to check along the wire of the winding. Damage to the insulation layer may cause a short circuit between the windings or between the winding and the core, which is an important manifestation of winding failure.
For some old Flying Shear Motors, due to long-term vibration, moisture and other factors, the insulation layer is prone to such damage.
2. Measure resistance
1. Phase-to-phase resistance measurement
Use a multimeter (for small Flying Shear Motor) or an insulation resistance meter (megohmmeter, for larger Flying Shear Motor) to measure the phase-to-phase resistance of the motor stator winding. Under normal circumstances, the phase-to-phase resistance of the three-phase winding should be basically equal (a certain error range is allowed, generally not more than 5%).
If the resistance value between two phases is significantly smaller than the resistance between other phases, there may be a phase-to-phase short circuit fault. For example, the normal phase-to-phase resistance is about 5Ω, but the resistance between two phases is measured to be 0.5Ω or even smaller, which is very suspicious.
2. Turn-to-turn resistance measurement (difficult to measure accurately, can be used as a reference)
For the measurement of turn-to-turn resistance, the bridge method (such as a double-arm bridge) can be used for more accurate measurement, but the operation is relatively complicated. In general, it can be roughly judged by comparing the DC resistance values ​​of different phase windings.
If the DC resistance of a phase winding is significantly smaller than that of other phases, there may be a turn-to-turn short circuit. However, the accuracy of this method is affected by many factors, such as the accuracy of the measuring instrument, the temperature of the winding, etc.
3. Measurement of resistance to ground
Use an insulation resistance meter to measure the insulation resistance of the winding to the ground (motor core). Under normal circumstances, the insulation resistance should be large (generally required to be greater than 0.5MΩ or according to the specific specifications of the motor).
If the measured insulation resistance to ground is very low (for example, less than 0.1MΩ), it indicates that the winding may have a short circuit to ground, which may be caused by insulation damage, moisture, etc.
III. Judgment of operating status
1. Abnormal start
When the Flying Shear Motor starts, if it is difficult to start, such as the motor makes a "buzzing" sound but cannot rotate normally, this may be a signal of winding failure. Winding short circuit or open circuit may cause the motor to have insufficient starting torque and fail to overcome the load to start normally.
Especially if there is obvious vibration during startup, and this vibration is not caused by mechanical parts (for example, the mechanical connection is normal, the coupling is not a problem, etc.), then the possibility of winding failure is greater.
2. Current and temperature during operation
During the operation of the motor, use an ammeter to measure the operating current of the motor. If the current increases abnormally (exceeds the rated current), after excluding mechanical reasons such as excessive load, it is likely that there is a short circuit fault in the winding, because the short circuit will reduce the impedance of the winding, resulting in an increase in current.
At the same time, monitor the temperature of the motor. If the motor temperature is too high (for example, when measured with an infrared thermometer, it is found that the temperature exceeds the normal operating temperature range), in addition to heat dissipation problems, winding failure (such as short circuit generates too much heat) is also a possible cause. You can touch the motor casing. If it feels very hot, you should further check the winding condition.
IV. Smell judgment
1. Burnt insulation smell
If you smell a pungent smell similar to burnt insulation material around the motor, this is likely a sign of a winding fault. This special smell is emitted when the insulation material is burnt due to a short circuit or overload of the winding.
This smell is quite unique and is significantly different from the smell of a normal motor during operation. Once you smell this smell, you should stop the motor immediately to check the winding condition.