Knife switch Also called knife switch switch Or disconnector, which is a simple and widely used type of hand controlled electrical appliances Low voltage electrical apparatus , as shown in the figure is a simple schematic diagram of knife switch (handle operated single-stage switch).
Knife switch is a switch with a moving contact knife switch, which is wedged (or separated) with the static contact knife holder on the base to connect (or disconnect) the circuit.
Applicable to AC 50Hz, rated voltage to 380V, DC voltage to 380V, DC voltage to 440V; In the complete set of power distribution device with rated current up to 1500A, it is used for infrequent manual connection and disconnection of AC and DC circuits or isolation. Including:
1. The single throw switch and double throw switch of the midpoint handle type are mainly used in the substation, which do not cut off the circuit with current and are used as the disconnector.
2. The side operating handle type knife switch is mainly used in the power box.
3. The knife switch of the midpoint front lever operating mechanism is mainly used in the switch cabinet for front operation and rear maintenance. The operating mechanism is installed in the front.
4. The side front operated mechanical knife switch is mainly used in the front two operation and front maintenance switchgear. The operating mechanism can be installed on both sides of the cabinet.
5. The knife switch with arc extinguishing chamber can cut off the current load, other Series knife switches are only used as disconnectors. Can't be misused
Circuit function
quarantine Power Supply To ensure the safety of circuit and equipment maintenance; Or for infrequently making and breaking loads below rated current
Breaking load, such as infrequently connecting and breaking low-voltage circuit with small capacity or directly starting small capacity motor.
When the knife switch is in the off position, it can be clearly observed to ensure the safety of circuit maintenance personnel.
Common types
Commonly used knife switches include HD type single knife switch, HS type double knife switch (knife shaped transfer switch), HR type fuse knife switch, HZ type combination switch, HK type knife switch, HY type reverse switch, HH type iron case switch, etc.
main parameter
1. Rated insulation voltage, i.e. higher rated working voltage;
2. Rated working current;
3. Rated working system: 8h working system and uninterrupted working system;
4. Use category: classified according to the nature of operating load and the frequency of operation. According to the frequency of operation, it can be divided into Class A and Class B. Class A is for normal use, and Class B is for those with few operations, such as those only used as disconnectors; There are many classifications according to the nature of operating load, such as operating no-load circuit, making or breaking resistive circuit, operating motor load, etc.
5. Rated making and breaking capacity: the rated making and breaking allowable current of the switching apparatus with making and breaking capacity;
6. Rated short-time withstand current;
7. Short circuit making capacity of electrical appliances with short circuit making capacity;
8. Rated (limited) short circuit current;
9. Operating performance: the number of operating cycles under rated operating current according to different use categories.
Composition classification
form
The knife switch is usually composed of insulating base plate, moving knife, static contact seat, arc extinguishing device and operating mechanism.
classification
1. According to different working principles, service conditions and structural forms, knife switches can be divided into knife switches, knife shaped change-over switches, open load switches (rubber covered porcelain bottom knife switches), closed load switches (iron shell switches), fuse knife switches and combination switches.
2. The knife switch can be divided into single comparison, double comparison and three comparisons according to the number of knives and the operation mode. The rated current of commonly used three phase switch is 100A, 200A, 400A, 600A, 1000A, etc. Generally, manual operation is adopted except for special high current knife switch and motor operation. The one with fuse link as moving contact is called fuse knife switch, which is called knife fuse switch for short.
The knife switch structure is called knife switch;
The combination switch is composed of stacked contact elements and rotary operation.
matters needing attention
The knife switch only used for power isolation does not need arc extinguishing device. The rated current of the high current knife switch used in electrolysis, electroplating and other equipment can reach tens of thousands of amperes. This kind of knife switch generally adopts the structure of multiple circuit conductors in parallel, and can be cooled by water to improve the current density that the knife switch conductor can carry.
Knife switch is required to be able to withstand the electrodynamic force and heat generated by short circuit current in the circuit. Therefore, in the structural design of the knife switch, it is necessary to ensure that the contact knife will not spring open, weld firmly or burn out under the action of a large short-circuit current. The knife switch required to break the load current is equipped with arc extinguishing devices such as fast blade or arc extinguishing chamber.
The knife switch can be divided into single knife switch, double knife switch and three knife switch according to the number of knife switches; According to the conversion mode, it can be divided into single throw knife switch and double throw knife switch; According to the operation mode, it can be divided into handle direct operation type and lever type knife switch. Figure 1 shows the circuit diagram of the three phase single throw knife switch, which can be used to turn on or turn off circuit A, or to isolate circuit A from the power supply. Figure 2 shows the single pole double throw knife switch, which can be used to turn on or turn off circuit A or circuit B, and can also switch the power supply to circuit A to circuit B.
The transfer switch is used for the main circuit to transfer one group of connected devices to another group of connected devices.
Product model: HD11FA-200/380
HD11FA-400/380
HD11FA-600/380
HD11FA-1000/380
HD11FA-1500/380
