1) According to the current nature of the main contact to make or break the circuit to choose DC or AC contactor. 2) According to the work task of the load controlled by the contactor, select the contactor of the corresponding use category. If the load is a general task, use the AC-3 use category; when the load is a heavy task, use the AC-4 use category. 3) Select the rated voltage of the contactor according to the voltage level of the controlled circuit. 4) Select the rated voltage level of the contactor coil according to the voltage level of the control circuit. 5) Determine the current level of the main contact of the contactor according to the power and operating conditions of the load. When the use category of the contactor corresponds to the work task of the controlled load, generally the current rating of the main contact of the contactor should be equal to or slightly larger than the current value of the controlled load. If it does not correspond, such as when AC-3 type contactor is used to control AC-3 and AC-4 mixed type load, the current level should be lowered for use. The selection of AC contactor can be carried out according to the following steps according to the type of load, working parameters and usage conditions: 1) Choose the type of contactor AC contactors are generally classified into one, two, three, and four types according to the type of load, which are denoted as AC1, AC2, AC3, and AC4. The corresponding control object of the first type of AC contactor is non-inductive or micro-inductive load, such as incandescent lamps, resistance furnaces, etc.; the second type of AC contactor is used for the start and stop of the wound asynchronous motor; the typical use of the third type of AC contactor is The squirrel cage asynchronous motor is running and disconnected during operation; the four types of AC contactors are used for the starting, reverse braking, reverse rotation and inching of the cage asynchronous motor. 2) Select the rated parameters of the contactor Determine the rated parameters of the contactor according to the controlled object and working parameters such as voltage, current, power, frequency and working system. 3) Series and parallel use of contactors Many electrical equipment are single-phase loads, therefore, several poles of a multi-pole contactor can be used in parallel. Such as resistance furnace, welding transformer, etc. When several poles are used in parallel, a smaller capacity contactor can be used. But it must be noted that the conventional heating current of the contactor after parallel connection is not completely proportional to the number of poles connected in parallel. This is because the resistance values ​​of the positive and static contact circuits are not necessarily the same, so that the current flowing through the positive is not evenly distributed. Therefore, the current can only increase to 1.8 times after the two-phase parallel connection, and the current can only increase to 2~2.4 times after the three-pole parallel connection. In addition, it should be pointed out that since the contacts of each pole connected in parallel cannot be connected and disconnected at the same time, the connection and breaking capacity cannot be improved. 4) The influence of power frequency For the main circuit, the change in frequency affects the skin effect. When the frequency is high, the skin effect increases. For most products, 50 Hz and 60 Hz have little effect on the temperature rise of the conductive circuit. However, attention needs to be paid to the attraction coil. When the attraction coil designed at 50 Hz is used at 60 Hz, the magnetic flux of the electromagnetic wire will be reduced, and the suction force will also be reduced. Whether it can be used depends on the margin of its design. Under normal circumstances, the user is best to use it according to its calibrated value, and place an order according to the operating power frequency used when ordering. 5) The influence of operating frequency The number of operating cycles per hour of the contactor has a great influence on the burning loss of the contact. Attention should be paid to the selection. The applicable operating frequency is given in the technical parameters of the contactor. When the actual operating frequency of the electrical equipment is higher than the given value, the contactor must be derated for use. Capacitive Touch Membrane Switch Capacitive Touch Membrane Switch,Capacitive Touch Switch,Capacitive Touch Sensor Switch,Capacitive Touch Light Switch CIXI MEMBRANE SWITCH FACTORY , https://www.cnjunma.com
var videoObject = {container:'.video', variable:'player', autoplay: true, html5m3u8: true, video: "https://vdse.bdstatic.com//b19bc1bab9ca8884f7eddbc1d69eaab1?authorization=bce-auth-v1%2F40f207e6485424f47b2e3df % 2F2017-05-11T09% 3A02% 3A31Z% 2F -1% 2F% 2F27d584426a3255e2578fd277a69ab4626692bf2df909149392072fc831c08bf6 "}; if (!! window.ActiveXObject) {videoObject.html5m3u8 = false} var player = new ckplayer (videoObject); AC contactor selection principles