What is a packet switch and what is it for?
Design
This unit was named because of the design features. The same type of switching elements are arranged on one axis and represent a single device. The picture below shows the design of a batch type circuit breaker.
The housing is made of electrical insulating material, with slots for fixed electrical contacts, equipped with arcing chambers. In the center is a movable washer made of insulating material, with electrodes located on it with knives. Several of these elements are located on one axis, with the help of which the apparatus is driven.
The figure below shows another type of packet switches - cam, or as it is also called biscuit. An electrical insulating casing with fixed and movable contacts located on it, supported by springs and located on guide insulators that abut against a movable figured washer, with recesses for guide pins.
You can learn more about the device of the bag from this video:
Operating principle
Consider how a packet switch works. So, the operator, turning the handle, drives the movable washers. They, in turn, transmit movement to the contact group, as a result of which switching occurs, the contacts open or close, depending on the initial position.
Disk packet switches have two switch positions: on and off. Cam switch it is possible to “program” and the switching of contacts will depend on the position of the switch itself.
Appointment
The load switch is also a disk circuit breaker, due to the simultaneous operation of the switches dialed into one case, they are often used as a power element to disconnect the load, electrical machines, power circuits. Also, the bag is needed to switch the load from one supply circuit to another (emergency input of the reserve).
The cam bag is used as an operating circuit control switch. It supplies power to the control circuit depending on the position of the switch, turning the controls on and off.
Application area
The picture shows the main types of package switches:
You could see them in electric boxes and drive boards (load switches).Some models are equipped with transparent viewing windows for visual monitoring of the state of the contacts, which allows you to verify the correct location of the device. Packets are used in control panels, operational switching, in substations for taking readings of values from a remote line, by operational personnel. In addition, batch switches are used in the cabs of drivers of electric power units: cranes, excavators and other mechanisms.
With the help of such a switch, the driver sets the speed and direction of rotation of the power unit, selects the mode of operation, using the closure of the group of contacts responsible for this parameter, the circuit section.
Often on linear diagrams of mechanisms you can see such a designation - command controller. This is the position of the group of contacts in the batch switch, for controlling the mechanisms by feeding in a certain order to the power control circuit.For clarity, we will analyze the control circuit of a two-speed electric motor.
The picture shows part of the switching circuit of the star-delta motor windings. Cam switch - command controller, indicated by the letters SM. In position 1, power is supplied to the circuit, the KV relay becomes self-locking, supplying power to the operational circuits regardless of the location of the controller key. In position 2, the starter KM1 is fed to the coil, which starts the engine according to the triangle scheme. When the device is switched to position 3, the KM1 starter coil is de-energized and fed to the KM2 and KM3 starters, which turn on the motor in a double star circuit.
We examined more detailed reviews of starters and control methods in our other articles. Now you probably know more about the purpose, principle of operation and the design of the package switch!
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