Generally speaking, when it comes to the winding machine's wire formation, we all know that it includes winding mechanism, wire arrangement mechanism, trimming mechanism, coil mold, demoulding mechanism, heating mechanism, tension mechanism, frame and so on. The slip ring of the winding machine is also an important part of the wire. If the slip ring of the winding machine becomes hot, the equipment stops working, which will have a great impact. Here, we will analyze the characteristics and maintenance of the slip ring of the winding machine:
1. The structure and principle of the slip ring of the winding machine.
The slip ring is composed of conductive ring, tail brush, brush holder, conductive rod, slip ring, slip ring cover and other components. The coils of the rotor are similar to the stator coils. The three-phase coils are connected in a star shape. The beginning of each coil is connected to three copper coils, and the coils are fixed on the coils. The ring and the ring, the ring and the shaft are insulated from each other, and are connected to the external circuit by a carbon brush that is compressed by a spring.
2. The development process of slip ring heating.
In normal operation, the temperature of the carbon brushes is generally between 50°C and 80°C (temperature rise is about 40°C), and the operating current of each carbon brush is between 20A and 100A. The pressure of the brush spring is relatively uniform, and the carbon brush can move freely without vibration. The heat generated during the operation of carbon brushes and slip rings is taken away by the ventilation system. In other words, heat generation and heat dissipation reach a basic balance. However, when the carbon brush becomes shorter, the contact resistance and additional resistance become larger, and the brush spring pressure becomes smaller. If the operating current increases, the system's balance ability will decrease when the temperature changes, and the temperature of some of the carbon brushes will increase, resulting in the temperature of the entire system. Will rise.
The third is the analysis of the cause of the slip ring heating.
(1) The cooling air volume of the slip ring is insufficient. When installed coaxially with the slip ring, it should be oriented accurately and conform to the structural design standards and regulations. The blade orientation does not meet the standard, on the one hand, it will cause bearing vibration, on the other hand, it will lead to insufficient cooling air volume of the slip ring, and cause the slip ring and brush to heat up.
(2) The closed air duct of the slip ring is blocked or leaked. The guide air inlet of the slip ring needs to be carefully cleaned to avoid the insufficient cooling air volume of the slip ring caused by dust accumulation and blockage, which may cause the brush and slip ring to heat up. During maintenance, use compressed air pipes to clean the slip ring holes one by one. Air duct leakage can also cause insufficient cooling air volume.
(3) The quality and maintenance factors of the brush. The mixed use of brushes or brush boxes causes some of the brushes to generate heat due to overcurrent, and even burn the leads. The brush was not carefully ground and polished when it was repaired and replaced. The gap is insufficient, the card gap is too large, and the contact surface of the slip ring is inconsistent. The uneven current distribution caused by the uneven length of the brush is a common cause of heating of the slip ring. Therefore, it is necessary to blow soot and clean regularly and measure the brush current.
(4) The reason for the insulation of the brush box conductor and the equalizing spring. An insulating gasket is installed between the conductive part and the fixed part of the brush box, and the current passes through the conductive part and the brush, and is introduced into the rotor through the slip ring. During the transportation, dust and carbon powder cause the insulation ability to drop or pass, and the uneven distribution of the resistance of each brush causes local heating. After the pressure equalization spring in the brush box is used for a certain period of time, uneven pressure, deformation, cracks, springs, etc. will appear, causing the brush box to over-current and heat up.
(5) The slip ring is not round or the surface is rough, resulting in friction heating. During maintenance, turning the slip ring causes the slip ring to be out of round or rough, which easily leads to friction heating.
(6) Bearing vibration causes the brush to heat up. The brush vibrates with the bearing, the friction of the brush contact surface is uneven, the wire and the spring are loose, local sparks occur, and the brush heat is further aggravated.
The fourth is the heat treatment method of slip ring.
(1) Treatment method for insufficient coaxial cooling air volume of slip ring. Take measures to increase cooling and ventilation, such as installing an external axial fan for cooling. When the temperature of the brush or slip ring is high, the fan can be started to enhance the surface heat exchange, and the cooling effect is ideal. Regularly use dry and clean compressed air to blow away the dust and powder of the slip ring, remove the dust from the slip ring cover, check and dredge the small holes of the slip ring after stopping, and check and clean the filter of the air inlet.
(2) Improve the maintenance quality of brushes, eliminate heating defects in time, and try to use the original brushes and brush boxes from the manufacturer. The carbon brush moves freely up and down in the brush holder. The gap between the carbon brush and the brush holder is 0.1~0.2mm. The brush has no bounce, shake, or astringency. The brush surface has no bright impurities. The spring pressure is adjusted to 11~12N, and the pressure is too small. Replace with a new brush or adjust the pressure, and the surface temperature of the slip ring should be below 120°C. In addition, if the brush is worn off by 2/3 of its height or the contact is poor, please replace it. The brush holder should be free of dirt. If the oxide film on the surface of the slip ring is too thick or the surface is rough or not smooth, please polish it with the finest emery cloth or white cloth. Coarse emery cloth is prohibited.
The slip ring heats up from time to time, which seriously threatens the safe operation of the winding machine. Therefore, monitoring, maintenance and timely handling of faults and damages of the slip ring and carbon brushes are one of the important tasks to ensure the long-term stable operation of the winding machine. The key to avoiding heat is prevention, which effectively solves the problems of slip ring heat and burnout.
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