Battery Rectifier Groups; With the development of technology, power electronic systems are used more and more in the electricity sector and become more important. Power electronics technology is used in high voltage, medium voltage, low voltage, automation or lighting systems, in short, in every field of electricity. The use of battery and rectifier groups, which are a supply and power electronics system in medium voltage distribution networks and substations, is of great importance.

The battery rectifier group consists of a semiconductor-based rectifier with constant voltage, automatic regulation according to the change in mains voltage, and battery groups, which meet the DC energy needs of the equipment in the transformer or DC distribution centers, which are constantly connected to the direct current loads found there.

In the substation where the battery rectifier groups are located, the motor and on-off coils of the medium voltage cells, lighting lamps, signal lamps, etc. supplies equipment. While the mains supply voltage is 220 VAC, the output voltage of the rectifier can be 24 VDC, 48 VDC or 110 VDC. In special productions, it can be 220VDC. We can group these structures in two parts as battery group and rectifier section.

Batteries consist of fully closed maintenance-free dry type (VRLA) batteries in accordance with TS 1352-3 EN 60896-22 / IEC 60896-22 standards. The nominal voltage of each battery is 12 VDC and the current carrying capacity can vary between 7 and 200 Ah. In addition, when carrying capacity is deemed necessary, the current carrying capacity of the batteries may be higher than these values.

Rectifiers, on the other hand, charge the batteries with a transformer, thyristor-controlled or IGBT/MOSFET-based high-frequency charging circuit when there is mains voltage in the circuit. When the mains energy is gone, the electrical energy stored in the batteries is transferred to the DC load feeds in the substation. Since the main task of the rectifiers is to charge the batteries in the system, it is of great importance to fully charge the battery during the charging process. The service life of an incompletely charged battery will be significantly reduced. If the rectifiers do not charge the battery in a balanced way, the battery will not be fully charged. Therefore, the correct selection of the rectifiers in the battery rectifier group is of great importance.

Battery rectifier groups are in a metal-enclosed structure where batteries are located in the lower part and rectifier circuits are located in the upper part. The protection class of this enclosure can be IP20, IP22 or IP 40, IP50 or IP51 depending on the application. The cooling method can be air-cooled natural circulation (AN) or thermostat-controlled air-cooled forced (fan) circulation (AF).

Another important feature of battery rectifier groups is the communication system. Depending on the application, battery rectifier groups can be compatible with SCADA. Battery rectifier groups compatible with SCADA work with a sufficient amount of dry contacts and remote communication protocols thanks to microprocessor controlled thyristor and switch mode type IGBT rectifier circuits. In this way, users are notified of fault signals in the battery rectifier group over an industrial communication protocol.

Battery rectifier groups are specified with rated output voltages and ampere-hour (Ah) values ​​of the battery. For example, the value of a battery rectifier group may be 24 VDC 26 Ah. Here, the input voltage of the rectifiers is 220/230 VAC and the operating frequency is 50 Hz, and it converts this voltage to 24 VDC with a semiconductor-based rectifier circuit and feeds the batteries when the mains is present. When the mains is gone, the batteries will supply DC loads with a current of 26 A for one hour.