The working environment of the motors in the aquaculture machines such as crushers and bait machines is poor. In operation, the operating conditions and operating conditions such as the heating conditions, current and voltage changes, and overload conditions should be monitored and properly maintained. . In this way, it can ensure that its useful life is properly extended. In addition, the operator should also be familiar with the principle and performance of the motor and master simple judgment and troubleshooting skills. 1 Monitor whether the three-phase current is balanced To ensure the normal operation of the motor, the three-phase current should be balanced. When the three-phase power supply voltage is unbalanced, it will cause three-phase current unbalance. If the unbalance value exceeds 10% of the rated current, the motor will obviously generate heat. In this case, the three-phase current and the three-phase power supply voltage should be checked first. If it is not balanced, it indicates that the motor has failed. 2 Whether the overload motor is overloaded can be determined by the following method: 2.1 Disengage the transmission and rotate the driven mechanical spindle by hand. To see if the spindle rotation is flexible, if the driven mechanical damage or dirty mechanism prevents the spindle from rotating flexibly, it is an overload. 2.2 Connect the ammeter to the power supply. When the motor is running at load, the reading of the ammeter is greater than the rated value on the motor nameplate, indicating that the motor may have an overload condition. Check if the load is too large. 3 Whether there are abnormal sound abnormalities mainly include: (1) the stator and the rotor are rubbed; (2) the rotor fan leaves the shell; (3) the rotor rubs the insulating paper; (4) the bearing is seriously deficient in oil; (5) There are debris in the motor. If there is an abnormal response, find out the cause and resolve it. 4 Check whether the body is overheated If the body overheating occurs, there are many reasons for this, which need to be checked as follows: 4.1 Measuring the power voltage When the three-phase power voltage is unbalanced, the three-phase current of the motor will be unbalanced, causing the stator windings to overheat. . As already mentioned. In addition, when the power supply voltage is too high, the back electromotive force, magnetic flux, and magnetic flux density of the motor increase. Since the amount of iron loss is proportional to the square of the magnetic flux density, the iron loss increases, causing the core to overheat. The increase in magnetic flux causes the excitation current component to increase, resulting in increased stator winding copper loss and overheating of the stator winding. When the power supply voltage is too low, if the motor's electromagnetic torque remains unchanged, the magnetic flux will weaken, and the rotor current will increase accordingly. Large, stator load current component increases, resulting in increased copper loss of the winding, so that the stator and rotor windings are overheated; the power line has a phase break or a phase of insurance fuse, or the blade, starter equipment contact burns, resulting in a Unreasonable, will cause three-phase motor two-phase operation, so that the two-phase windings overheat by high current. 4.2 Checking the load The motor is not matched with the production equipment, the power of the production machine is greater than the rated power of the motor, the motor is overloaded for a long time, (long-term low-speed operation) will lead to overheating; the production equipment will be equipped but the work is not normal. Runtime load is large and small, (such as the pulverizer feed is often too large) will overload the motor and heat; with the production machinery itself has a failure, such as the rotation is not flexible, etc., will also cause the motor windings to overheat. 4.3 check the motor condition If the three-phase power supply and the production machinery are all normal, it should be the motor has a fault, we must first check the external and easy to check the place, such as: should use the delta connection of the motor wrongly connected into star, motor Bending of the shaft, poor assembly, bearing quality problems, poor ventilation, excessive dust inside the motor, etc. 5 Check whether the motor shell is energized The motor shell energized will cause danger to the operator. If this phenomenon occurs, it is important to check whether the motor is seriously dampened and the insulation of the stator winding is weakened. The insulation performance is reduced; the lead-out line and the junction box are in contact with each other; the local insulation winding is damaged Causes the wire to touch the shell; if the ground wire fails, the terminal board is damaged or the surface is oily. During the inspection, you can use a test pencil test or touch the metal part of the machine with the back of the hand to feel it. 6 Check if the stator windings are open circuit. There are obvious hum noises during operation. The rotation speed is low and the operation is difficult. The three-phase currents are unbalanced. Check the power supply voltage is no fault, you can initially think that the motor stator winding a phase disconnection, you need to open the junction box, with a multimeter resistance file detection 1 ~ 4; 2 ~ 5; 3 ~ 6 between the terminals whether the path, (upper row Left to right 1, 2, 3; lower row 6, 4, 5). A pair of terminals is blocked, indicating that the phase winding is open. 7 Judging whether there is a short circuit in the stator windings The light-load starting is acceptable, but the current is obviously greater than the normal value, and the current is not balanced. The motor vibrates and is noisy. It quickly generates heat, and the starting is weak. If it can not be started with the load, it will be burned when the power is turned on. Basically, it can be concluded that there is a short circuit fault in the stator windings. If it does not have the repair conditions, it should be sent out for repair. When judging and inspecting faults, it is often encountered that some fault phenomena are similar, but the causes of the faults are different. Carefulness and patience are required. When a fault is not found according to a certain idea, it is necessary to replace one of the ideas. It is forbidden to estimate the cause of the failure without analysis in order to avoid an accident. Author: College of Fisheries, Hebei Agricultural University
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