What is a cam switch and what is it for?
What it is?
Cam switches (in the photo below) are electrical devices that are needed for switching in electrical circuits of both alternating and direct current. They found application for switching power control circuits of equipment, as well as in the operational control circuit of other electrical devices. Devices can be used in low-voltage circuits and in circuits with voltage up to 500 V - for alternating current (frequency 50-60 Hz) and up to 220 V DC.
They are made of high quality insulating and conductive materials, and are created using successful experience in creating modern technology, as well as knowledge gained in the development of switching devices. The cam switches are characterized by their small size, they are resistant to short-term overload in the circuit, and also have good switching capabilities. To protect them from short-circuit current in the electrical circuit, you need to use fuses with fuse links.
Design
From the very name of this device it is clear that the design is due to the use of "cams", which actuate a certain "pusher". The cam switch device requires a group of switching elements, changing the position of which you can achieve a certain location for the operation of different switching circuits. The location of contacts and cams is called a switching program (its purpose is to assemble a specific connection diagram). They are located inside the plastic case, which is made on the basis of melamine.
You can clearly see the design of the device in the diagrams below:
Such a housing is immune to electric arcs and eddy currents. The design of the cam switch makes it possible to turn on and off all contacts almost simultaneously. This is ensured by the fact that the cam of one element is connected mechanically with other cams. The use of silver in a contact device, which is better than the same copper withstands an electric arc, provides good switching characteristics and increased wear resistance. The switch must be clearly fixed in a certain position, which requires a locking drive mechanism. Also in the design there is a movement limiter of the drive. Its purpose is to clearly set the switch in the extreme position.The drive or shaft of the apparatus is a square rod. For reliable operation and good contact switching, it must be made of metal in order to withstand the load when scrolling. This is very important where motor control is used. To control the drive of the switch, a handle made of insulating material is used.
The cam switch device is demonstrated on video from one of the top manufacturers of sockets and switches, ABB companies:
Principle of operation
The principle of the cam switch is based on the inclusion of a specific group of contacts by rotating the apparatus drive. Rotating the handle to the desired position, the drive rotates around its axis and drives the cams located on it. They, in turn, close a certain group of contacts. To understand how the contact group works, you need to look at the switching diagram, which is compiled on the basis of the necessary connection diagram. When the drive is in the desired position, the switch is fixed in it using a special locking mechanism and the circuit starts its work. To return to the zero position, it is necessary to turn the handle again. According to the principle of action, they are divided into switches with automatic return of the handle to the position and manual.
Appointment
Cam switch is needed for:
- control mechanisms that are driven by three-phase and single-phase motors, to change the connection of the windings of AC motors (star-delta), change the direction of rotation;
- control and signaling in operational circuits;
- can work as a switch, switch operating positions of the electric welding machine;
- switching the necessary connection of the resistance group;
- ensuring switching of operating modes of heating equipment;
- turning on and off the drive mechanism of the sectional disconnector in transformer substations.
Application area
These devices are used in everyday life, in industrial production, at power supply facilities, in river shipping, on sea vessels, in floor railless electric vehicles. Their purpose is also the management of mechanisms in agriculture. With the help of such a switch, a bypass connection can be arranged. It is used to withdraw from the equipment circuit or a section of the circuit, to carry out repair or maintenance work.
Finally, we recommend watching a useful video on the topic:
So we examined the device, the principle of operation and the purpose of the cam switch. We hope the information was useful and understandable to you!
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