The customer, a company that is part of a large multinational corporation, offers complete, integrated infrastructure solutions for the global rail industry.
As in other UPS projects, a rectifier transformer and an inverter transformer are required, but with the addition of some features peculiar to the railway field due to quality requirements and compliance with specific regulations.
SPECIAL ORTEA TRANSFORMERS FOR RAILWAY UPS
In order to create the hexaphase electrical system required for the 12-pulse rectifier (the latter used to contain the current ripple to the grid), an isolation transformer with two secondaries that together form the two three-phase triads (hexaphase system) is essential.
The isolation transformer for the rectifier must be made with two secondaries to feed the two three-phase bridges of the converter which, in addition to adapting the mains voltage to the bridge voltage, must fulfil other characteristics of which the main ones are:
- Vcc% of 10% between primary and secondary, in order to further reduce the harmonic content of the current, an integrated reactor (shunt) must be inserted.
- Vcc% of 20% between the two secondaries to reduce overcurrents on the SCRs of the converter (this is possible with the correct vertical spacing between the two secondary windings).
- A very low no-load current so the core technology is intercalated laminations.
As far as the inverter is concerned, on the other hand, it is necessary to insert a specific step-up transformer downstream to adapt the output voltage from the battery to the mains voltage.
The three-phase transformer inserted at the inverter’s output, in addition to fulfilling the function of adapting the output voltage by bringing it to 400V, is realised with an air leakage reactance that implies a Vcc% of 6%, which allows current harmonics to be contained. In addition, the core must support the thermal effect of the voltage harmonics injected by the inverter.
Both machines are made from high quality grain oriented laminate and designed such that they do not exceed thermal class B (80°C overtemperature) and comply with the IS732 Railway Standard in addition to the standard regulation.
The design challenge was complicated by the stringent dimensions, the many features to be met and, last but not least, the very restrictive thermal class.
THE MARKET REWARDS ORTEA’S TECHNOLOGICAL SOLUTIONS
Thanks to its decades of experience, Ortea is able to design and manufacture UPS transformers to meet the most complex requirements, as this successful case demonstrates.
Ongoing partnerships with the world’s leading manufacturers provide evidence of the high degree of reliability achieved.
Find out more about the features of Ortea’s isolation transformers: https://www.orteanext.com/applications/technology-applications/unprotected-loads/
