Switch mode rectifiers for cathodic protection Cathodic protection (CP) is a technique used to control the corrosion of a metal surface by making it the cathode of an electrochemical cell. A simple method of protection connects the metal to be protected to a more easily corroded...
1. Switch mode rectifiers for cathodic protection
Cathodic protection (CP) is a technique used to control the corrosion of a metal surface by making it the cathode of an electrochemical cell. A simple method of protection connects the metal to be protected to a more easily corroded "sacrificial metal" to act as the anode. The sacrificial metal then corrodes instead of the protected metal. For structures such as long pipelines, where passive galvanic cathodic protection is not adequate, an external DC electrical power source is used to provide sufficient current.
Cathodic protection systems protect a wide range of metallic structures in various environments. Common applications are: steel water or fuel pipelines and steel storage tanks such as home water heaters; steel pier piles; ship and boat hulls; offshore oil platforms and onshore oil well casings; offshore wind farm foundations and metal reinforcement bars in concrete buildings and structures. Another common application is in galvanized steel, in which a sacrificial coating of zinc on steel parts protects them from rust.
2. Why Green Power's switch mode power supplies replace SCR rectifier?
Green Power's Switch mode power supplies have many advantages over SCR rectifier, therefore, they are now more and more used for electroplating process to replace SCR rectifier.
The main advantages of Green Power pulse plating rectifiers over thyristor rectifiers include but not limited to:
Light weight, small size, in far areas, don't need crane truck, like heavy oil-cooled SCR rectifier which is difficult and expensive.
Same high reliability as SCR rectifier, long time 7 days 24 hours continuous running
High conversion efficiency, power saving at least 15% than SCR rectifier.
Not affected by power fluctuation, 100% output, don't need extra capacity
IGBT rectifier adopts AC-DC-AC-DC topology, 3 phase AC is firstly converted to DC, which has capacitors for energy charging and discharging, it will suppress power fluctuation, so rectifiers don't need bigger capacity than actual use.
SCR rectifier doesn't have energy buffer function, it is affected directly by the grid power fluctuation, so it always keep much extra capacityand increase user's investment cost.
Pulse output needs less plating time, customer feedback 40% shorter time needed for plating
-Rectifier won't break down: in case of one module failed, the rectifier continue working with reduced power
-Less downtime and easy recovering:plug-in structure, replace module directly, downtime is shorten to minimum, this reduces potential high cost of your plant stop and increase your plant's availability.
-Current expansion available:thanks to the modular design and supporting parallel connection, if you need more power, you only need to add more modules.
-Reduce current rating to save power: if you don't need all modules working, you can switch off some modules, rectifier can work at lower rating.
-Less floor space occupied: the rectifiers can be built on top of each other, making them easy to fit into your plant's design, optimizingfloor space.
-Easy to install and maintain: each rectifier consists of up to ten modules and naturally two or more stacks can be connected to allow higher currents (40kA) and voltages (200V DC).
-Separate output or parallel running output available: you can let the rectifier module separate output to connect to more tanks, or parallel connecting to get higher current for one tank.
-Compact size, modular structure, e.g. air cooling 1000A 12V size only 450*560*300mm, weight is only 58kg. much less size and weight than SCR rectifier, don't need forklift
Low pollution to grid, power factor 0.93
Lower costfor the same specification
3. Comparison chart of the rectifiers
At least 1/2 smaller than SCR type
Response time to load variation
very high (≈1ms)
1/1000 of max current or voltage
easy in current and voltage mode
Losses at no load /Vout ON
Losses at no load /Vout OFF
Fast in both voltage and current mode
fastest in both voltage and current mode
4. Main Technical Parameters of the rectifiers
Input voltage: 3 phase 4 line, 220V, 380V, 415V, 480V
Input voltage protection range: +/-10%
Cooling method: Water cooling, forced air cooling, natural cooling
Power factor: 0.93
Efficiency: 92% at rated output
Regulation range: 0-100%
Duty cycle: 100% continuous running
Control mode: constant voltage, constant current
Ambient temperature: Max. 40℃
5. Advantages of the rectifiers
Convenient use and operation
Easy to move and replacement
Flexible combination, get different current output
Compact size, light weight
Save space, could be installed stacked
Standard design, short lead time, lower cost
Easy remote control by communication
DSP digital control support multiple remote control option:
0-10V/4-20mA analog signal+dry contacts to be controlled by PLC
Communication with PLC through RS485, Profibus, Profinet
We provide remote control box, distance up to 30 meters long
Touch panel operation
Could set output value accurately
Could set step length
Could realize timer function, automatic stop after timing up
Could set protection parameters on touch panel
Could save history data for inquiry
Set local control/remote control
Set CC/CV mode
Easy and quick fault judge and troubleshooting
Rectifier provide full protections and self alarm
DSP realize self fault diagnosis
Touch panel shows protection type automatically
Touch panel provide history protection record for inquiry
Provide detailed troubleshooting guidance with pictures in manual
User-oriented mechanical design, easy for disassembly to change parts
Look for IP54 Cathodic Protection Rectifier, for Pipelines, Ships, Desert and Harsh Environment, coming from Green Power Technology, is of high precision, high efficiency and reliable performance, which has already been exported to USA, Germany, India, etc and owned good reputation. Customized service is also available if you need.