Motor failure cause analysis and maintenance processing method
1. The winding is damp or wet by water: the winding is heated and dried.
2, insulation dirt or aging: cleaning and drying, painting treatment, if aging, need to replace the insulation.
3. The terminal block is damaged or the lead wire touches the terminal box casing: repair or replace the terminal block or junction box, and the lead wire is covered with insulation.
4. The power cable and grounding wire are connected incorrectly: Correct the wiring error.
1) The voltage is too low to make the motor unable to start. When the motor cannot start after the three-phase power is turned on, the possible causes are as follows:
(1) The specified connection of the motor shall be a triangular (△) connection, but it is connected in a star shape (Y) and its load is heavier;
(2) The distance between the power source and the motor is too far and the wire is too thin, so that the power supply voltage applied to the motor end at the time of starting is too low;
(3) The voltage of the line of the power supply is too low.
For the case that the motor cannot be started because the voltage is too low, the following measures can be taken after the verification and verification:
(1) The wrong connection can be corrected to a star (Y) connection and corrected to a delta connection;
(2) Minimize the length of the power supply line and increase the cross section of the conductor as appropriate;
(3) Appropriately increase the output voltage of the low voltage side of the transformer according to the actual situation.
2) After the power is turned on, the motor only has a click, but it cannot be normally started when the motor starts. This may be caused by:
(1) The three-phase power supply is not fully connected;
(2) The loaded agricultural machinery is dragged due to the failure;
(3) The initial end of the stator winding lead wire is connected incorrectly or the internal wiring of the winding is reversed and connected incorrectly;
(4) One phase open circuit of the stator winding or the rotor winding;
(5) The number of fixed rotor slots is improperly matched (usually occurs in the motor after the pole change).
If the motor occurs during the start-up process, it will be treated separately after testing and verification:
(1) Carefully check each pair of contacts of the power line, motor lead-out line, fuse, and switch to find out the location of the open-circuit fault to be eliminated;
(2) Check the reason why the dragged agricultural machinery is stuck and handle it;
(3) The wrong end of the lead wire is corrected after being detected;
(4) The breaking fault of the stator and rotor windings can be detected by the multimeter and the megohmmeter, and then reconnected;
(5) If the number of rotor slots is not matched properly, it can be reasonably solved by taking the appropriate outer diameter of the rotor or selecting the appropriate stator winding span and replacing the new rotor.
3) It is difficult to start the motor. After the rated load is applied, the speed can not reach the rated speed. The motor is difficult to start. The possible reasons for the speed not reaching the rated speed after the rated load is as follows:
(1) The power required by the load machinery is too large or the transmission mechanism is stuck;
(2) improper selection and adjustment of overload protection equipment;
(3) There is a phase disconnection in the external circuit or stator winding;
(4) There is a short circuit in the stator winding or the rotor winding;
(5) The inner end of the motor stator winding is connected incorrectly;
(6) The cage rotor is broken or desoldered, and the winding of the wound rotor winding is loose;
(7) The bearing of the motor is damaged.
When the motor has the above fault condition at the start, it can be handled as follows:
(1) Check in detail whether the power of the load machine and the motor is properly matched. Otherwise, the motor with a larger capacity should be selected or the load should be reduced; if the transmission mechanism is stuck, the cause should be identified and excluded;
(2) If the selection and adjustment of the overload protection equipment is improper, the setting value may be adjusted appropriately; if the overload protection is continuously operated, the motor capacity may be selected too small, and the appropriate motor may be replaced or the drag may be reduced. Dynamic load
(3) For the disconnection fault, the detection of the disconnection may be made by a megohmmeter or a multimeter, and the fault shall be handled as appropriate;
(4) If the stator or rotor winding is short-circuited for individual coils, it can be repaired by local repair. If the winding short-circuit range is large and the fault is serious, the burnt coil must be replaced or all re-winding;
(5) If the inner end of the motor winding is connected incorrectly, the motor end cover should be disassembled, and the low-voltage DC power supply of about 6V should be connected to each phase winding in turn, and phase-checked by the compass method to find the fault, and then correct according to the regulations. Correct the wrong wiring;
(6) The broken or unsold welding of the cage rotor should be treated according to the severity of the fault, respectively, by repair welding or replacement of the new rotor; if the motor bearing is indeed damaged, the new bearing of the same type should be replaced. If the winding of the wound rotor winding is loose, it is usually possible to use visual inspection, quantity resistance, etc. to find out the fault and repair it.
4) This kind of failure occurs when the melt blown motor of the knife switch is started when the motor starts. The possible causes are as follows:
(1) Motor phase loss starting;
(2) The connection line between the start control switch and the motor has been short-circuited;
(3) The motor power is too small or the mechanism of the dragged load is stuck;
(4) The melt cross section is selected too thin or damaged;
(5) The stator winding of the motor is grounded or short-circuited;
(6) The starting resistance of the wound rotor motor is too small or has been short-circuited.
If the above situation occurs in the motor at start-up, it can be handled as follows:
(1) Carefully check the power cord, motor lead-out line, fuse, and switch contacts to find out if the fault is connected or disconnected;
(2) Check the insulation of the switch to the motor cable, find the short-circuit point and re-bundle to eliminate the fault;
(3) Appropriately reduce the load dragged by the motor or eliminate the fault of the dragged load mechanism;
(4) The selection of the melt should be based on the protection against short-circuit and overload starting, and the melt should not be required to protect the motor from overloading;
(5) For the grounding or short-circuit fault of the stator winding of the motor, it can be detected by megohmmeter, high-voltage test bench or multimeter, bridge meter and short-circuit reconnaissance to find the exact location of the fault and repair it;
(6) Carefully check the starting resistance value of the wound rotor motor. If the value is too small, increase the resistance and eliminate the short circuit.
5. Abnormal heating of the motor at start-up and abnormal heating and smoke generation when the smoke motor starts, the possible reasons are:
(1) The power supply voltage is too low, causing the motor to generate excessive temperature rise under rated load;
(2) The power supply voltage is too high, so that the magnetic core of the stator core is too high under the rated load, so that the temperature rise of the motor is too high;
(3) The motor starts frequently or the number of positive and negative reversals is too high, and the strong starting current causes the winding to generate high temperature;
(4) The motor is poorly ventilated or the temperature of the working environment is too high;
(5) The stator winding has a short-range short circuit or ground fault, which causes local heating or smoke of the motor after starting;
(6) The cage rotor broken strip or the wound rotor winding wiring is loose, and the rotor heats up under the rated load, so that the temperature rise of the motor is too high;
(7) The motor is seriously overloaded or the mechanical load of the dragged load is poorly lubricated, causing the entire motor to heat up;
(8) The motor end cover is deformed or the bearing is damaged, so that the stator and the rotor are severely rubbed and heated.
If the motor generates abnormal heat or smoke for the above reasons, it can be treated as follows:
(1) Firstly, the voltage of the motor at no load and load should be detected. If the no-load voltage is too low, the output voltage of the transformer should be appropriately increased. If the voltage drop is too large for the load, the thicker power line should be used to reduce the line voltage drop;
(2) If the power supply voltage exceeds the specified standard, the output voltage of the power supply transformer should be lowered to appropriately reduce the voltage of the power supply line;
(3) For motors that are frequently started or have a large number of positive and negative reversals, the number of starting and reversing, reversing, or replacing the electric motor that can adapt to frequent starting and positive and negative reversing can be reduced;
(4) When the motor is poorly ventilated or the ambient temperature is too high, check whether the fan of the motor is damaged and its fixing condition, and carefully clean the air passage of the motor to prevent blockage. At the same time, the high temperature heat source near the motor is isolated;
(5) Partial short circuit or ground fault of the stator winding can be used to find the fault location by the instrument, and treat it as appropriate according to its fault range and severity;
(6) For the broken bar of the cage rotor, the motor can be connected to a three-phase AC power supply with a lower voltage (about 15%-30% of the rated voltage), and the stator current is measured at the same time, if the cage rotor winding has For broken bars or desoldering faults, the stator current will change correspondingly with the rotor position. After the broken or unwelded position of the cage rotor winding is found, the repair or replacement of the new rotor may be performed as appropriate. When the wire of the wound rotor is loose, it can be tested with an electric resistance meter and a multimeter to find out that the wiring is loose and re-wired and fastened;
(7) If the motor is fixed or the rotor is rubbed, if it is caused by deformation of the end cover or bending of the shaft, the machining should be corrected. If the bearing is damaged, the new bearing should be replaced.
