What are the common faults of high-voltage motors?

The common faults of high-voltage motors are mainly concentrated in three categories: electrical system, mechanical structure, and auxiliary system. The phenomena, causes, and handling methods of different faults have significant differences.
一、 Electrical system failure (most critical and frequent)
Electrical faults directly affect the safety of motor operation and are often related to windings, insulation, or wiring, as follows:
1.Winding short circuit/ground fault
Phenomenon: Motor startup tripping, smoke and heat generation during operation, extremely low insulation resistance value (close to 0).
Common reasons: Aging and damage of winding insulation, contact with the casing or other windings; The motor is affected by water and moisture, resulting in a decrease in insulation performance; Long term overheating of the winding accelerates insulation damage.
Solution: After power failure, use a megohmmeter to check the insulation resistance and confirm the short circuit/grounding point; Disassemble the motor stator, repair or replace damaged windings; Dry damp motors to restore insulation performance.
2.Winding open circuit fault
Phenomenon: The motor cannot start, there are no signs of operation, or the current is abnormally high and accompanied by abnormal noise after starting.
Common reasons: Welding points of winding leads falling off; The winding wire was burned off due to overload or overheating; The winding is broken due to mechanical impact during transportation or installation.
Solution: Use a multimeter to detect the continuity of the winding and locate the position of the circuit breaker; Re weld the detached lead wire. If the wire burns out, it needs to be rewound or the winding needs to be replaced
3.Stator/rotor grounding fault
Phenomenon: When the motor casing is live (due to poor grounding), the leakage protector trips, and the insulation resistance between the casing and the winding does not meet the standard.
Common reasons: The insulation of the stator winding is damaged and comes into contact with the casing; The rotor squirrel cage bar is broken or the end ring is loose, resulting in insulation damage between the rotor and the shaft; Metal foreign objects enter the interior of the motor, piercing through the insulation layer.
Solution: Thoroughly clean the inside of the motor and remove foreign objects; Repair the insulation of the stator winding and replace damaged rotor components; Check and reinforce the grounding device to ensure that the grounding resistance meets the requirements (usually ≤ 4 Ω).
二、 Mechanical structural failure (affecting operational stability)
Mechanical failures are often caused by improper installation, wear, or maintenance, which can easily lead to vibration, noise, and other issues, as follows:
1.Bearing damage fault
Phenomenon: The motor produces a “buzzing” or “clanging” abnormal noise during operation, the temperature at the bearing end cover is too high (exceeding 80 ℃), and the amplitude of motor vibration increases.
Common reasons: insufficient, deteriorated or mixed impurities of bearing lubricating grease; The installation of bearings is too tight/too loose, resulting in abnormal radial/axial clearance; The fit tolerance between the motor shaft and the bearing exceeds the standard, resulting in uneven long-term stress.
Solution: After stopping the machine, remove the bearing end cover and replace the damaged bearing; Clean the bearing chamber and add new lubricating grease of the appropriate model (filling amount is 1/2-2/3 of the bearing chamber volume); Check the roundness and fit tolerance of the shaft, and repair the shaft if necessary.
2.Shaft bending/wear fault
Phenomenon: The motor operates with severe vibration, there is a “sweeping” noise (metal friction sound) between the rotor and stator, and the belt pulley/coupling is eccentric after installation.
Common reasons: motor overload or sudden shutdown, bending of the shaft due to impact stress; The bearing was not replaced in a timely manner after being damaged, and the shaft was worn out due to long-term uneven stress; Poor alignment between the shaft and the load (such as fans and pumps), resulting in long-term exposure to radial forces.
Solution: Use a dial gauge to check the curvature of the shaft, and straighten it if it exceeds the allowable value; Severely worn shafts need to be repaired with chrome plating or spray coating, or replaced with new shafts directly; Adjust the alignment accuracy between the motor and the load again to ensure that the coaxiality meets the standard.
3.Fixed rotor “sweeping chamber” fault
Phenomenon: There is a strong metallic friction sound during motor operation, local overheating and discoloration of the stator core, and possible wear and breakdown of the winding insulation.
Common causes: Bending of the shaft or damage to the bearings, resulting in rotor eccentricity; Loose or deformed stator core, uneven gap with rotor; Foreign objects entered the motor and got stuck between the stator and rotor.
Solution: Immediately shut down the machine to prevent the fault from escalating; Repair bent shafts or replace damaged bearings, adjust the clearance between the stator and rotor; Remove internal foreign objects, check whether the stator core is deformed, and repair it if necessary.
三、 Auxiliary system malfunction (indirectly affecting motor operation)
The auxiliary system includes cooling, lubrication, protection devices, etc. Its faults are easily overlooked, but can indirectly cause motor damage, as follows:
1.Cooling system malfunction
Phenomenon: The operating temperature of the motor continues to rise (exceeding the rated temperature rise), the temperature control protection device trips, and the motor efficiency decreases.
Common reasons: Damage to the fan of the air-cooled motor or blockage of the air path; The cooling water pipeline of the water-cooled motor is blocked, leaking, or the water pump is malfunctioning; Insufficient cooling medium (such as coolant) or high temperature.
Solution: Clean the air duct and heat sink of the air-cooled motor, and replace the damaged fan; Clear the water cooling pipeline, repair the leakage point, and check the operation status of the water pump; Supplement or replace the cooling medium to ensure normal flow and temperature of the cooling system.
2.Protection device malfunction
Phenomenon: When the motor is running normally, the protective device trips incorrectly, or when the motor malfunctions, the protective device does not operate.
Common reasons: incorrect parameter settings for overcurrent and overheating protection; The protective device (such as relay, thermostat) itself is damaged; Detect faults in circuits such as current transformers and temperature sensors.
Solution: Recheck and correct the parameters of the protective device to ensure they meet the rated value of the motor; Replace damaged protective devices or detection components; Check the wiring of the protective circuit to ensure good contact.