For the convenience of production, sales, management and use, China has compiled models for various low-voltage electrical appliances according to regulations. That is, the full model of the low-voltage electrical appliance is composed of the category code, the group code, the design code, the basic specification code and the auxiliary specification code.
The type designation of low-voltage electrical appliances and its meaning:Derived code can be added after each level code. The meaning of the full model of the product is shown in Figure 1.
All parts of the low-voltage electrical appliance must be represented by the specified symbols or numbers, which means:
1, class code
Including the category code and the group code, expressed in Chinese Pinyin letters, representing the category to which the low-voltage electrical components belong, and the group to which the same type of appliances belong.
2, design code
Represented by numbers, indicating different design sequences of similar low-voltage electrical components.
3, the basic specification code
Represented by numbers, indicating different specifications in the same series of products.
4, auxiliary specification code
Represented by numbers, indicating different products in the same series and products of the same specification with some difference.
Among them, the combination of the class code and the design code represents the series of products, generally referred to as the serial number of the appliance. The use, working principle and structure of the same series of electrical components are basically the same, and the specifications and capacities can be as many as needed. For example: JR16 is the serial number of thermal relays. The structure and working principle of the same series of thermal relays are the same; however, the rated current of the thermal components ranges from a few amps to several tens of amps, and there are more than ten specifications. Among them, the auxiliary specification code is 3D, which has a 3-phase heat element and is equipped with a differential phase-failure protection device, so it can have overload and phase-break protection functions for the three-phase asynchronous motor. The meanings of the low-voltage electrical group code and derivative code are shown in Table 4-1 and Table 4-2.
(1) Fuse
Role: severe overload and short circuit protection
Graphic symbol:
Text symbol: FU
(2) Combination switch
Function: It is used as a lead-in switch for power supply on machine tools. It can also be used to switch on and off small current circuits.
Graphic symbol:
Text symbol: SA
(3) Push button switch
Role: send a manual control signal in the control circuit
Graphic symbol:
Text symbol: SB
(4) Automatic air switch
Function: Under the normal working conditions of the circuit, it is used as the infrequent connection and disconnection of the line, and can automatically break the circuit when the circuit is overloaded, short-circuited and lost.
Graphic symbol:
Text symbol: QF
(5) AC contactor
Function: frequently turn on or off the AC/DC main circuit and large-capacity control circuit at a long distance.
Graphic symbol:
Text symbol: KM
(6) Thermal relay
Function: Mainly used for protection of overload protection, phase failure protection and current unbalance operation of electric motor.
Graphic symbol:
Text symbol: FR
(7) Time relay
Role: Switch on or off the controlled circuit at the required time interval
Graphic symbol:
Text symbol: KT
(8) Speed ​​relay
Function: The speed of the rotating speed signal is used as the command signal, and the contactor is used to realize the reverse braking of the motor.
Graphic symbol:
Text symbol: KS
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