Automatic circuit breaker A3700

The switch (Fig. 1, a) is intended for automatic protection of electrical installations of direct and alternating current up to 630 A. It has a manual control of the handle 7, but it can also have an electromagnetic motor drive EMF acting on this handle.

The circuit for remote control of the machine is shown in Fig. 1, b.

Figure: 1. Automatic switch A-3700 (a) and circuit for remote control of the machine (b):

QF - switch, KA - electromagnetic release, XVD - semiconductor block connector, RD - remote release, EMF - electromagnetic remote drive, XPS - drive connector, Vpr - voltage of the remote drive, TA - current transformers, SB1 and SB2 - remote drive buttons, SA1 and SA2 - auxiliary contacts, SQ - limit switch

The remote control drive includes: XPS plug connector for connection to external circuits, SQ limit switches and SA2 auxiliary contact and the EMF drive itself, consisting of electromagnets connected by a mechanism with the handle 7 of the switch.

During maintenance, after checking the contacts, control buttons, limit switch, make a test remote switching on and off the machine using the drive and make sure that it works correctly.

Undervoltage releases - electromagnetic KA and remote RD - using the ХVD connector can be connected to the system of the semiconductor unit 8 and with the help of the handle 9 (Fig. 1, a) they can adjust the release current, current setting, shutdown time. The semiconductor release acts on the release device via a shunt release, which consists of a core with a coil and a yoke.

For remote control of an automatic machine with an electromagnetic drive, a push-button post is connected, consisting of two normally closed buttons SB1 and SB2, and other connections, shown in the figure with a dotted line with a dot, are made with the XPS drive connector. Supply voltage Upr. The position of the buttons I corresponds to the off position ("off"), position II - on ("on").

The switch is designed to operate without changing any parts under normal operating conditions. The circuit breaker consists of a body 1 (Fig. 1, a), a cover 5, a contact system 6, 13 and 14, a control mechanism, arc extinguishing chambers 4, a flame arrester 3, an electromagnetic 11, 12 overcurrent release, clamps for connecting external wires 2, transformers current 10 (for alternating current) and additional nodes.

After opening the short circuit and periodically once a year, as well as for changing and adjusting the release parameters, which include the rated current of the release, setting the current and operating time in the short circuit zone, it is necessary to inspect and partially disassemble the breaker, which is performed as follows: remove cover 5 and flame arrester 3, protective shield, control unit 8 or a cover that covers the clips and switch cover, assess the lever (pawl) with the retaining rail, for which carefully turn the rail until it splits with the pawl, remove the arc chutes 4 with the arc chute ... Using the handle 9 of the block of semiconductor releases, the parameters of the release are adjusted by removing the previously transparent plate that covers the scale.

The switch and its components must be kept clean. Once a year, the pivot joints of the remote control switch should be lubricated with petroleum jelly, the switch, and the remote control with spindle oil.

The screws fixing the switch, its cover, the flame arrester, the control unit, the cover covering the clamps must be tightened to the full. When inspecting the switch, all accessible places must be cleaned of soot with a clean cloth moistened with gasoline. In addition, the plates of the arc chute should be cleaned of the metal that has got there (avoiding electrical short circuit with metal drops). It is prohibited to file contacts (from traces of metal, carbon or soot) in order to give them a smooth surface. During inspection, it is necessary to check the dips of the contacts for the thickness of their sintered layer, if it turns out to be less than 0.5 mm, the switch is not suitable for further operation.

Automatic circuit breaker AP-50 fig. one.

This model was produced in the Soviet Union rice. 2.

And this is a modern modification of fig. 3.

Complete disassembly of the switch is necessary when the contacts are damaged and need to be replaced.

In most cases, when it is necessary to eliminate defects in the thread of the contacts, arcing lattice, clean the soot on the inner surface and parts of the circuit breaker, or replace the return spring, it is enough to limit ourselves to partial disassembly.

To do this, unscrew the screws securing the cover to the base 1 and remove the cover.

Remove the arc chute, release the lever 8 (if the switch is cocked} by pressing the stop button 2 or the rail of the output wires traverse.

For further disassembly, unscrew the screws 7 and remove the fixed 5 and movable 6 contacts.

When breaking or loosening with pliers, remove the return spring 9 from the holder.

Figure: 4 (a - c). Automatic circuit breaker AP-50:

1 - base, 2 - stop button, 3 - lever, 4, 7, 8 - screws, 5 - fixed contact, 6 - movable contact, 9 - return spring, 10 - arc chute, 11 - cover, 12 - terminals , 13 - steel plates, 14 - flexible connection, 15 - traverse, 16 and 17 - electromagnetic and thermal releases

After the parts are repaired, the machine is assembled in the following sequence: the arc-extinguishing chamber 10 is installed in the socket, the articulated joints of the mechanism are lubricated with instrument oil, the rotation of the traverse on the axle should be without sitting.

Install fixed and movable contacts and fix them with screws.

A return spring is installed, screws 8 are screwed in to connect the output wires, a cover with arc chutes is put on the base and tightly fixed with screws, avoiding distortions.