In the industrial and mining enterprises, the higher the motor power used, the more heat is generated, and the higher the temperature of the motor windings. In order to make the motor work normally, cooling water is often used for the motor. Heat exchange to achieve the purpose of cooling and cooling. However, in actual work, often because of improper operation or accidents, such as forgetting the water valve, accidental water shortage or insufficient water flow during operation, the temperature of the motor will rise sharply in a short period of time, causing its insulation to deteriorate. If it is not found in time, there will be the possibility of burning the motor. The No. 7 and No. 8 cement mills of our company use the 2500 kW water-cooled asynchronous motors produced by Lanzhou Electric Machinery Factory. Since the cement mill was trial-produced in 1997, within one year, due to negligence and accidental water cuts, the temperature of the motor windings was increased twice, causing some damage to the motor. In March 1998, the author added a water-cut protection interlock device to the No. 7 and No. 8 cement grinding motor. Eliminated the occurrence of similar incidents and received good control results. Two kinds of water-cut protection simple control circuits that are applied in practice are introduced for the counterparts. 1 The transistor protection circuit can be used as a water cut protection switch. The microphone connector can be used as a probe for water flow. However, the best method is to use an automobile spark plug (available at auto parts stores) because the housing of the automobile spark plug is a metal conductor and has mounting threads. Easy to install â–¡ â–¡ Tang Quansheng. In addition, the housing and the middle electrode are insulated from each other. After the spark plug is threadedly installed on the water pipe, the housing communicates with the pipe, so the entire pipe can serve as another electrode of the control circuit, as shown. Note: Select the horizontal position of the pipe as the mounting point for the spark plug, and the spark plug should be installed in the vertical pipe. The purpose is to prevent the residual water droplets from hanging between the middle electrode and the case and the base of the transistor and the power supply negative when the water is cut off. Turn on. Working principle: When the pipeline has cooling water, the base of the transistor V is connected with the negative pole of the power supply, the transistor V is turned on, the DC relay KA is closed, the normally open contact is closed, and the motor is allowed to close and start; when the pipeline is dry The base of transistor V is open, the transistor V is cut off, and the KA relay of the DC is released, so that the motor cannot be closed or the motor trips during operation. Note: (1) 12 is the reamer motor (or hoist). The intermediate relay relay points KA0 and KI of the oil pump motor are respectively the pressure loss and overcurrent intermediate relay interlock points. 2 The electric contact pressure gauge is used as the water shortage protection switch. Practical experience proves that the use of a crystal transistor as the water protection switch has the following disadvantages. : First, improper installation of the spark plug, there is no vertical installation, easy to cause water droplets between the middle electrode and the shell and can not be tripped when inadvertent closing or water cut; Second, the middle electrode and the shell electrode will be severely oxidized for about one year , So that the motor can not be closed, and due to serious oxidation, the replacement of spark plugs more difficult; Third, the lack of water, can not achieve the purpose of water protection. In view of the above situation, the author improves the control circuit and adopts another effective method, namely using the electric contact pressure gauge as the water shortage protection switch. In the past three years, there have been no cases in which the motor windings have increased in temperature due to water cuts and water shortages, resulting in a very good control effect. In order to use the electric contact pressure gauge, it is possible to effectively prevent the poor conduction due to the oxidation of the surface of the metal electrode. For example, the electric contact pressure gauge is installed vertically above the cooling water horizontal pipeline, and the movable contact of the electric contact pressure gauge is low. Two leads of the static contact of the water pressure set point are drawn. (1) When there is water pressure in the pipeline, the pressure gauge has a pressure indication (water pressure action value setting can be based on the actual situation). When the water pressure is enough, the movable contact is connected with the set static contact, the intermediate relay KA acts, the normally open contact is closed, the closing circuit of the motor is switched on, the motor is allowed to start 3(2) when the pipeline is cut off or When the water flow is insufficient, the movable contact of the electric contact pressure gauge is disconnected from the set static contact, and the intermediate relay loses power, so that the motor cannot be closed or the motor is tripped during operation, thereby causing the motor to perform timely water cut or deficiency. Water protection, with a slight change, this circuit can also be applied to other places where water shortage is controlled. Tianjin Quanquan Qi 7tt eye company ventilation tube (canvas belt): 1 for large-tonnage bulk cement trucks, features: Airless Address: No. 42 South Hongji Road, Nankai District, Tianjin City H8/H11 Led Headlight,H11 Led Headlight Bulb,H11 Led Headlight,H8 Led Headlight CHANGZHOU CLD AUTO ELECTRICAL CO.,LTD , https://www.cld-led.com