Main electrical model and parameters

Commonly used main electric appliances include buttons, travel switches, universal transfer switches, and master controllers.

The main electrical appliance is a switching electrical appliance used to switch on and off the control circuit to issue commands or to program the production process. It includes control buttons (referred to as buttons), travel switches, master switches, and master controllers. There are also foot switch, proximity switch, reverse switch, emergency switch, toggle switch and so on.

This article mainly introduces the button switch, and the type and parameters of the travel switch, follow the small series to learn more.

First, the button switch

Push button switch: an electric appliance that turns on or off a small current circuit for a short time. It does not directly control the on/off of the main circuit, but sends a manual "command" in the control circuit to control the contactor, relay, etc., and then To control the main circuit, it is called "master electric appliance".

Button switch appearance

Button switch structure

The structure of the push button switch is composed of a button cap, a return spring, a fixed contact, a movable contact, a casing and a strut link.

Normally open contact (moving contact): refers to the contact in the original state (the appliance is not subjected to external force or the coil is not energized), and the fixed contact and the movable contact are separated.

Normally closed contact (moving contact): refers to the contact in the original state (the appliance is not subjected to external force or the coil is not energized), and the fixed contact and the movable contact are in a closed state.

Normally open (closed) button switch. When not pressed, the contact is open. When pressed, the contact is closed. When released, the push button switch is reset and opened under the action of the return spring. In the control circuit, the normally open button is often used to start the motor, also known as the start button.

The normally closed (open) button switch is opposite to the normally open button switch. When the button is pressed, the contact is closed, and when the button is pressed, the contact is broken; when the hand is released, the button switch is reset and closed under the action of the return spring. . The normally closed button is often used to control motor parking, also known as the parking button.

The model meaning of the button switch:

Main technical parameters of the push button switch

Button switch installation and use

(1) When installing the buttons on the panel, they should be neatly arranged and arranged reasonably, which can be arranged from top to bottom or left to right according to the order in which the motors are started:

(2) The installation and fixing of the button should be firm and the wiring should be reliable. Applying a red button means stopping, green or black means starting or powering up, don't make a mistake.

(3) Since the distance between the button contacts is small, if there is a short circuit fault such as oil, the contact should be kept clean.

(4) The button board and button box of the installation button must be metal, and try to connect them to the main grounding busbar of the machine. For the hanging button, a special grounding wire must be provided, and the metal pipe should not be used as the grounding wire.

(5) When the button is used in high temperature, it is easy to make the plastic deformation and aging and cause looseness, causing the contact screw to be short-circuited. The insulating plastic tube can be installed at the wiring screw to prevent short circuit.

(6) The button with indicator light is heated by the lamp. It is easy to deform the plastic lamp cover for a long time. The lamp voltage should be reduced and the service life should be prolonged.

(7) The “Stop” button must be red; the “Emergency Stop” button must be a red mushroom head; the “Start” button must have a protective retaining ring, and the protective retaining ring should be higher than the button head to prevent accidental actuation and electrical equipment errors. action.

Commonly used push button switch models

Commonly used push button switches are LA2, LA4, LAl0, LA18, LA19, LA20, LA25, LA32, LA38, LAY1, LAY3, LAY4, LAY6, LAY37 (PBC) and other products.

Second, the limit switch

The travel switch, also known as the limit switch, can be mounted on a relatively stationary object (such as a fixed frame, a door frame, etc., referred to as a still life) or a moving object (such as a train, a door, etc., referred to as an animal). When the animal approaches the still life, the contact of the switch's linkage drive switch causes the closed contact to break or the open contact to close. The operation of the circuit and mechanism is controlled by the change of the opening and closing state of the switch contacts.

How the travel switch works

In actual production, the travel switch is installed in a pre-arranged position. When the module mounted on the moving part of the production machine hits the travel switch, the contact of the travel switch acts to realize the switching of the circuit. Therefore, the stroke switch is an electric appliance that switches the circuit according to the stroke position of the moving part, and its function is similar to that of the button.

Travel switch classification and model meaning

Main technical parameters of the travel switch

How to choose the stroke switch

Mainly consider the application, control object, protection level, rated voltage, rated current, contact type and quantity. The structure of the direct-acting limit switch is similar to that of the push button. The disadvantage is that the split speed of the contact is related to the speed at which the mechanical moving part (stop) pushes the push rod.

When the moving speed of the moving parts is lower than 0.4 m/min, the speed of the contacts is broken and closed, and the arc is easily burned out. The roller type or micro-motion limit switch with the momentary mechanism should be selected.

What are the commonly used travel switches?

Commonly used travel switches are LX3, LX8, LX10, LX19, LX21, LX23, LX25, LX29, LX33, LXK3, LXP1 (3SE3) and other products.