General characteristics of cathodic protection transformer rec
tifiers:
The rectifier transformer is one of the main components of the cathodic protection system with the current injection method, whose task is to rectify alternating current and inject electric current into the structures under protection. Rectification of alternating current in the rectifier transformer is done by semiconductors, the main transformer is used to supply the output voltage. Due to the fact that rectifier transformers are constantly working, the characteristics and environmental conditions of the rectifier transformer panel and cooling type are taken into consideration during the construction stages. According to the progress of science and technology and the needs of the industry, the technology of manufacturing and controlling the rectifier transformer has also made significant progress. In this way, every day we see many innovations in this industry, such as making transformers, smart rectifiers, photovoltaics, etc.
In cathodic protection systems with the method of current injection (impressed current), rectifier transformers are used to inject electric current into the structures under protection. The working principle of the rectifier transformer is to straighten the input alternating current, inject and stabilize the current to the structure under protection (converting the input alternating current to DC output). Cathodic protection rectifier transformers suitable for working in different environmental conditions such as: humid, dusty, salty, inside the electrical room, etc. are made to work permanently under full load under the following conditions:
Maximum temperature with shade: 50 degrees Celsius
Maximum temperature of metal surfaces that are directly exposed to sunlight: 80 degrees Celsius
Maximum relative humidity: 95%
Isochronic level: 60 (occurrence of 60 lightning days per year)
Approximate dust concentration: 70 to 1400 milligrams per cubic meter
Transformers, rectifiers and all its accessories must be guaranteed in the mentioned working conditions and made according to BS, IEC, IPS, IGS, NPCS standards. In several different parts of this educational content, the general characteristics of this equipment including; Cooling systems, electrical information, transformer, rectifier rectifier, different control methods of rectifier transformer, tank and panel, protection control panel, electrical diagrams, installation mechanism and manufacturing standards of this new device are described.
Types of rectifier transformer cooling systems
A) Oil cooling (ONAN)
In order to increase the reliability of the device in harsh conditions, rectifier transformers are made with oil cooling. In this type of rectifier transformer, the rectifier bridge and the desired filters are immersed in oil, the oil inside the tank is equipped with a level display, oil temperature and moisture absorber (silica gel). This type of cooling system is called ONAN (in some cases, a fan is used to cool the oil, and this system is called ONAF for short).
b) air conditioner cooling (AN)
According to the conditions of use of transformer rectifiers, the power of the device may be so low that as a result of making a rectifier transformer with that power and oil cooling it is not cost-effective. has offered This type of transformer rectifiers are usually made in the ranges of 10 to 50 volts and 5 to 30 amperes, but based on the demand, the design and production of air-cooled transformer rectifiers in higher powers is also possible. This type of cooling system is called AN.
The degree of protection of oil-cooled and air-cooled transfer rectifiers is considered IP42 to IP65 (according to the customer’s request).
Electrical information
A) Alternating current (AC) input
The input of the device can be single-phase or three-phase according to its rated power. The input voltage in single-phase devices is 230/220 volts, 50 Hz, and in the three-phase type, 400/380 volts, 50 Hz. The device should be designed and built in such a way that up to 10% fluctuation in the input power voltage does not cause a malfunction in its operation and does not cause any damage to it.
b) direct current output (DC)
Transformer rectifiers made by Brena Electronics are made in different ranges from 2 to 250 volts and 5 to 500 amperes according to the customer’s request. According to the transformer standard, the mentioned rectifiers have the ability to supply current to the cathodic protection system at an ambient temperature of -20 to +50 degrees Celsius.
