Common methods of the hottest drying motor winding

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Common methods for drying motor windings and problems needing attention

(1) there are many methods for drying motor windings. The most common methods are bulb drying and current drying

① bulb drying method. The simplest method is to remove the rotor of the motor, place the stator vertically, and hang the high-power bulb of more than 100 watts in the stator core chamber. Note that the bulb should not be too close to the winding to avoid damaging the coil insulation. Cover the motor with wood or canvas to reduce heat loss. The motor can also be placed horizontally. Put the bulb in the lower part of the stator chamber, place iron wires around the bulb to prevent the coil insulation from being damaged, and cover the shell with heat-resistant materials for insulation. If the inner diameter of the stator is large, put more bulbs or increase the power of the bulbs. As the bulb is close to the coil, the drying temperature is generally kept at about 100 ℃. Measure the insulation resistance after drying for about hours. When the qualified resistance value can be maintained for 6 hours, the drying can be completed. If there is an infrared bulb, the effect is better. A drying wooden box can also be self-made. According to the size of the motor, two 300 ~ 500 watt bulbs can be arranged on both sides, not close to the winding, so as to avoid damaging the local insulation of the coil. During the drying process, pay attention to monitor the temperature in the box and do not exceed the allowable range

② current drying method. Remove the rotor of the motor, connect the three-phase stator windings in parallel or in series (large and medium-sized motors usually adopt series connection due to small winding impedance), connect a rheostat in series, and then connect it to a 220 V one-way AC power supply to heat and dry the windings. Since there is no rotor in the stator, the rheostat must be used to adjust the current so that the current is 50~70% of the rated current of the motor to control the heating temperature of the winding. If there is a single-phase voltage regulator, the rheostat may not be used. The 220 volt power supply enters the winding after voltage regulation

if there is a three-phase autotransformer, the 380V three-phase power supply can be connected to the stator winding with the rotor removed through the three-phase voltage regulator, and the line voltage of the winding can be adjusted to 7 ~ 15f% of the rated voltage of the motor (that is, the line voltage can be adjusted to 27 ~ 57 V)

(2) pay attention to the following points when drying the motor winding:

① clean it before drying, especially in the stator cavity

② adjust the control temperature at any time. The temperature shall not exceed the maximum heat-resistant temperature allowed by the insulation grade of the winding. Thermometer method: Class A shall not exceed 90 ℃, class E shall not exceed 105 ℃, and class B shall not exceed 110 ℃. When measuring temperature, the thermometer shall be close to the winding of the part to be measured, and the contact part shall be isolated from the air as far as possible

③ during heating, in order to avoid winding insulation expansion and cracking; The heating temperature shall rise gradually, and the temperature rise rate shall not exceed 30 ℃/hour generally

④ during the drying process, the insulation resistance of the winding shall be measured at any time (generally once every hour with a megger), and records shall be made. When the insulation resistance is stable for 6 hours (generally more than 5 megohm), the drying can be completed

⑤ in the drying process, all countries are accelerating the use of the Internet to transform and upgrade traditional industries and cultivate and develop emerging industries. In order to keep warm, it is also a "breathtaking leap" proposed in Marxist economics. In addition to necessary ventilation to eliminate moisture, the motor should be isolated from the surrounding air as far as possible

⑥ when the current drying method is used, the shell of the pusher with electric optimal structure must be reliably grounded

⑦ the current heating drying method shall not be used for motors that are very wet or wetted by water. Because when the electronic universal testing machine is selected for rapid temperature rise, the insulation will expand and crack, so the external heating method should be used. At the same time, the temperature rise rate should be controlled at about 8 ℃/hour; Or when heating

to 50 ~ 60 ℃, keep it for 3 ~ 4 hours, and then heat it after most of the moisture is removed

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