1. Use According to the capacity (kilowatt) of the three-phase squirrel cage asynchronous motor, determine the current (amplifier) ​​of the melt in the switch and fuse. Optical Rotary Sensor,Custom Encoder,Optical Encoder 6Mm Shaft,Handwheel Pulse Generator Jilin Lander Intelligent Technology Co., Ltd , https://www.jllandertech.com
2. The switch of the three-phase squirrel-cage motor with the port, the multiple relationship of the melt (A) to the motor capacity (kW):
Switch start, kW by 6
Melt protection, kW by 4
3. Description The mouth refers to a three-phase 380 volt squirrel cage motor.
1 small squirrel cage motor, when the starting is not frequent, the iron shell switch (or other protective cover switch) can be used.
Start directly. The capacity of the iron-shell switch (A) should be safe for the motor's "6 times the kilowatt-hours". This is because the starting current is large. The motor capacity of such a direct start with a switch should not exceed 10 kW at most, and is generally less than 4.5 kW.
[Example 1] 1.7 kW motor switch start, with 15 amp iron shell switch.
[Example 2] 5.5 kW motor switch start, with 30 amp iron shell switch (calculated as 33 amps, should be equipped with 60 amp switch. However, due to more than 30 amps, considering economics without affecting safety, you can choose 3 0 Ann.)
[Example 3] The 7 kW motor switch is started with a 60 amp iron case switch. For switches that are not used to "direct start" the motor, the capacity does not have to be considered "6 times", but can be smaller.
2 Squirrel-cage motors usually use fuses for short-circuit protection, but the melt current in the fuses must be considered to avoid large currents during starting. For this purpose, the general melt current can be selected as the motor "4 times the kilowatts".
When selected specifically, the same as the iron shell switch, should be selected according to product specifications. It is not convenient to introduce here. However, the specifications of the fuse (soft lead wire) are not uniform, and are still represented by numbers, see Table 3-1.
The fuses can be installed separately in front of the magnetic starter or in combination with the switch (eg a capacitor in the iron housing switch). If the selected melt appears in use: "Fuse when starting", the cause should be checked. If there is no short circuit, the starting current may not be avoided. At this time, it is allowed to change the first-stage melt (or two stages if necessary), but it should not be larger.