Knife switch selection and installation precautions

1. Open load switch (text symbol QS )

 

( 1 ) Structure and symbol of open load switch

 

 

        

　

( a ) Structure of the knife switch                                            　 ( b ) the symbol of the knife switch

Knife switch

 

( 2 ) Selection method

 

1 For the lighting circuit, a two-pole switch with a rated voltage of 220V or 250V and a rated current equal to or greater than the maximum operating current of the circuit can be selected .

 

2 For the direct start of the motor, a three-pole switch with a UN of 380V or 500V and a rated current equal to or greater than three times the rated current of the motor can be selected .

 

( 3 ) Installation precautions

 

1 The rubber cover knife switch must be installed vertically on the control panel or switch board. It cannot be flipped, that is, the handle is facing up when the state is on. Otherwise, the knife switch may loosen and fall in the disconnected state, causing false connection.

 

2 When installing the wiring, the pile head on the knife gate is connected to the power supply, and the lower pile head is connected to the load. When the wiring is connected, the incoming and outgoing lines cannot be reversed. Otherwise, an electric shock may occur when the fuse is replaced.

 

3 When operating the rubber cover knife switch, it can't carry heavy load, because the HKl series porcelain bottom cover knife switch does not have a special arc extinguishing device, it only uses the cover of the rubber cover to prevent arc burn.

 

4 If you want to carry a general load operation, the action should be rapid, so that the arc is extinguished faster, on the one hand, it is not easy to burn the human hand, on the other hand, the arc damage to the moving contact and the static clamping seat is also reduced.

 

2. Closed load switch

 

Closed load switch ( also known as iron case switch ): It is a kind of switch that is improved on the basis of the knife switch. It is composed of a knife switch, a fuse, a quick-break spring, etc., and is housed in a metal case. The switch is operated by the side handle and is provided with a mechanical interlocking device, so that the cover cannot be closed when the cover is opened, and the cover cannot be opened when the knife switch is closed, thereby ensuring safe use of electricity. The quick-break spring between the handle and the base makes the switch open and close quickly, and the arc-extinguishing performance is good. The enclosed load switch can work in dusty places.

 

Iron shell switch installation and use precautions

 

(1) In order to ensure safety, the switch housing must be connected to a good grounding wire.

 

(2) When connecting the switch, tighten the wiring to prevent the insulation inside the switch from being burnt out.

 

(3) For safety, a mechanical interlock is installed on the steel shell of the iron shell switch. When the shell cover is opened, it cannot be closed; after closing, the shell cover cannot be opened.

 

(4) When installing, first fix the fixing parts, fix the wooden switchboard with the fasteners on the wall or the pole, and fix the iron shell switch on the wooden switchboard.

 

(5) The iron shell switch should be installed perpendicular to the ground. The installation height is convenient for manual operation, usually around 1.3 to 1.5m .

 

(6) The power supply line of the iron shell switch and the output line of the switch must pass through the inlet and outlet holes of the iron shell. When installing the wiring, install a rubber washer at the inlet and outlet holes to prevent dust from falling into the iron shell.

 

(7) When operating, it must be noted that the iron shell switch must not be opened or closed, and the closing is generally performed with the left hand. If the fuse is replaced, it must be done after the brake is applied.

 

3. Fuse type knife switch

 

The fuse type knife switch is also called a fuse type isolating switch, and is an isolating switch which is a fuse body or a load carrying member with a fuse body as a moving contact. Commonly used models are HR3 , HR5 series, rated voltage AC 380V (50H2) , DC 440V , rated current to 600A . The fuse type knife is used in the power distribution circuit and the motor circuit with high short-circuit current, and is used as a power switch, an isolating switch, an emergency switch, and as a circuit protection, but generally not used as a direct switch single motor. The fuse-type knife switch is a combination of various low-voltage power distribution device knife switches and fuses.

TO-220 package

TO-220 Transistor Outline Package is a type of in-line package often used in high-power transistors and small and medium-sized integrated circuits.

It not only plays the role of mounting, fixing, sealing, protecting the chip and enhancing the electrothermal performance, but also connects to the pins of the package shell with wires through the contacts on the chip, and these pins pass through the wires on the printed circuit board. Connect with other devices to realize the connection between the internal chip and the external circuit.Because the chip must be isolated from the outside world to prevent impurities in the air from corroding the chip circuit and causing electrical performance degradation. On the other hand, the packaged chip is also easier to install and transport.

TO-220 package is a kind of in-line package that is often used for fast recovery diodes. TO-220AC represents a single tube with only two pins and only one chip inside.

The diodes are packaged in TO-220AC and can be used in switch mode power supplies (SMPS), power factor correction (PFC), engine drives, photovoltaic inverters, uninterruptible power supplies, wind engines, train traction systems, electric vehicles and other fields.

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