Most often, cam switches are used for switching electrical circuits, in particular for controlling electric motors. In this article, we will introduce you to the main features of this device, telling you how it works, what it consists of and why it is needed at all. Photo and video examples will allow you to learn even more about the device, the principle of operation and the purpose of the cam switches.
Content:
- What it is?
- Design
- Principle of operation
- Appointment
- Application area
What it is?
Cam switches (pictured below) are electrical devices that are needed for switching in both AC and DC electrical circuits. They have found application for switching power circuits for controlling equipment, as well as in the operational circuit for controlling other electrical devices. The devices can be used in low-voltage circuits and in circuits with voltages up to 500 V - for alternating current (50-60 Hz) and up to 220 V direct current.
They are made from 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. Cam switches are small in size, withstand short-term overload in the circuit, and have good switching capacity. To protect them from short-circuit current in the electrical circuit, you need to use fuses with fusible links.
Design
From the very name of this device it is clear that the design is due to the use of "cams" that drive a "pusher". The cam switch device assumes the presence of a group of switching elements, by changing the position of which it is possible to achieve a certain location for the operation of different switching schemes. The arrangement of contacts and cams is called a switching program (its purpose is to assemble a certain connection diagram). They are located inside a melamine-based plastic housing.
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 cam switch design allows all contacts to be turned on and off almost simultaneously. This is ensured by the fact that the cam of one element is mechanically connected to the other cams. The use of silver in the contact device, which withstands an electric arc better than that of copper, provides good switching characteristics and increased wear resistance. The switch must be clearly fixed in a certain position, which requires a locking mechanism of the drive. Also in the design there is a limiter for the movement 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 bar. For reliable operation and good contact switching, it must be made of metal to withstand rotational stress. This is very important where motor control is used. A handle made of insulating material is used to control the switch drive.
The cam switch device is clearly demonstrated in the video from one of the the best manufacturers of sockets and switches, by ABB:
Principle of operation
The principle of operation of the cam switch is based on the inclusion of a certain group of contacts by rotating the device drive. By rotating the handle to the desired position, the drive rotates around its axis and actuates the cams located on it. They, in turn, close a certain group of contacts. To understand how a group of contacts works, you need to look at the inclusion diagram, which is drawn up on the basis of the required connection diagram. When the actuator is in the desired position, the switch is fixed in it using a special latching mechanism and the circuit begins its work. To return to the zero position, it is necessary to turn the handle again. According to the principle of operation, they are divided into switches with automatic return of the handle to the position and manual.
Appointment
A cam switch is needed for:
- control mechanisms that are driven by three-phase and single-phase motors, for changes in the connection of the windings of AC motors (star-delta), changes in direction rotation;
- control and signaling in operational circuits;
- can work as a switch, switch of working positions of an electric welding machine;
- switching the required connection of the resistance group;
- ensuring switching of operating modes of heating equipment;
- switching on and off the drive of the section disconnector mechanism in transformer substations.
Application area
These devices are used in everyday life, in industrial production, at power supply facilities, in river navigation, on sea vessels, in floor-mounted trackless electric vehicles. Also, their purpose is to control mechanisms in agriculture. With this switch, a bypass connection can be established. It is used to withdraw equipment or a section of the circuit from the diagram, to carry out repair or prevention 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 for you!
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