VA series circuit breakers for rated currents of 250 A

The BA51 and BA52 series circuit breakers have rated currents of 250, 400 and 630 A and are intended for use in electrical installations with voltages up to 660 V AC and up to 440 V DC. The two-digit number 35, 37 or 39 following the serial number means the rated current of the circuit breaker 250, 400 or 630 A respectively.

Switches provide protection against short-circuit currents, overloads and unacceptable voltage drops, as well as the infrequent switching on and off of electrical circuits. They have electric thermal and electromagnetic current releases, but they can only be done with electromagnetic release.

The nominal currents of thermal releases have the following values: 100, 125, 160, 200, 250 A — for AB BA51 (52) -35; 250, 320, 400 A — for automatic circuit breakers of the BA51 (52) -37 series; 400, 500, 630 A — for breakers BA51-39, 250, 320, 400, 500, 630 A — for breakers BA52-39.

The ratio of the tripping current of the electromagnetic releases to the rated current of the thermal releases (breaking ratio) is within 10-12.The specified ratio (breaking ratio) applies to AC circuit breakers. Circuit breakers with thermal overcurrent releases shall operate at a current equal to 1.25 times the rated current of the release for less than 2 hours (hot).

In fig. 1. the protective characteristics of the BA51 (52) -35 series circuit breakers are shown

Rice. 1. Protective characteristics of the circuit breakers of the BA51 (52) -35 series: zones of characteristics from cold (1) and heated (2) states, zones of action of electromagnetic overcurrent release at direct (3) and alternating (4) currents .

Automatic switches VA53 (55) -37 have rated currents of 160, 250, 400 A; switches BA53 (55) -39 -160, 250, 400, 630 A. The purpose and operating conditions are the same as those of the switches BA51, VA52 described above.

Circuit breakers of the BA53 series are current limiting, the BA55 series are selective with a time delay in the area of ​​short-circuit currents. The circuit breakers have semiconductor overcurrent release and allow stepwise adjustment of the following parameters:

• rated release current: 0.63; 0.8; 1.0 rated breaker current. For example, for a circuit breaker with a rated current of 160 A, the rated release current during adjustment can be set to 100, 125 and 160 A;

• settings for operating current in the area of ​​short-circuit currents, a multiple of the rated release current: 2, 3, 5, 7 and 10 — for alternating current; 2, 4 and 6 — for direct current;

• 4, 8 and 16 s overload current zone response time settings (with six times AC and five times DC);

• response time settings in the area of ​​short-circuit currents for circuit breakers of the BA55 series: 0.1; 0.2 and 0.3 s — for alternating current; 0.1 and 0.2 s — for direct current.

The time settings operate in the selectivity zone, which is limited by the short-circuit current value of 20 — 28 kA, depending on the particular type of circuit breaker. Above the limit of the selectivity zone, the switches are actuated without time delay.

The tripping current in the overload zone (starting current) is 1.25 times the rated tripping current for all circuit breakers.

Circuit breakers of the VA75-45 series have one value of the rated release current — 2500 A; VA75-47 have a maximum release with a rated current of 2500 or 4000 A. The specified values ​​of the rated currents of the releases are also considered the rated currents of the circuit breakers. The protective characteristics of the switches are shown in fig. 2.

Rice. 2. Protective characteristics of circuit breakers of the VA75-45 series (47) on direct (a) and alternating (b) current: with releases 1600, 2000, 2500 A and settings in current zones of overload 4, 8, 16 s and zones of short-circuit currents — 0.1 and 0.2 s

The switches are intended for installation in electric circuits with a nominal voltage of alternating current up to 660 V and direct current up to 440 V and are used for the protection of electrical installations in case of overload and short circuit, as well as for infrequent switching on and off of electric circuits at nominal modes on work.

The circuit breakers have semiconductor overcurrent release and allow stepwise adjustment of the following parameters:

• rated release current: 0.63; 0.8; 1.0 rated breaker current;

• the settings for the operating current in the short-circuit current zone are multiples of the rated release current: 2, 3, 5, 7 — for AC circuit breakers with a release of 2500 A; 2, 3, 5 — for AC circuit breakers with 4000 A release; 2, 4, 6 — for DC circuit breakers with 2500 A release and 2, 4 — for DC circuit breakers with 4000 A release;

• 4, 8 and 16 s overload current zone response time settings (with six times AC and five times DC);

• response time settings in the area of ​​short-circuit currents (up to the upper limit of the selectivity area) 0.1; 0.2; 0.3 s — for AC switches and 0.1; 0.2 s — for DC switches.

The selectivity area is limited to 36 and 45 kA (rms) for AC circuit breakers with 2500 and 4000 A releases, respectively, and to 50 and 60 kA, respectively, for VA75-45 and VA75-47 DC circuit breakers.