In the disproportionately growing Chinese cities with over a million inhabitants the infrastructure for local passenger traffic will be considerably enhanced over the next years.

Complex underground networks will be built especially in the cities of Shanghai, Shenzhen and Guangzhou. A dc-dc converter designed for this promising market is currently being mounted in the new underground trains for Guangzhou.
The new dc-dc converter with 25kW output power has been developed by SMA in Niestetal. Its task is the electrically separated conversion of the 1000 - 2000Vdc contact wire voltage into an output voltage of 110Vdc. The converter charges a 110VNiCd battery and feeds the 110Vdc public grid.
The system power electronics fulfil the strict demands of Chinese underground operators. The fully resonantly switching inverter topology allows operation based on natural convection alone. Another highlight is the fact that the converter is available within a very short period of time. After enablement it starts charging the battery and feeding consumers in the train within less than two seconds. The battery is charged with temperature compensation and current limitation freely configurable within a range of 10 to 210A. Output current limitation has been implemented to protect the device against extreme external temperatures, allowing for continuous battery charging.
A special under-floor container has been constructed for the converter which includes additional components. A battery switch box from the customer Bombardier Transportation has been integrated. With a maximum height of only 480mm the container is ideally suited to fulfil the conditions in underground operation.
The converter was developed and designed and the under-floor container constructed by SMA in Niestetal on behalf of the joint venture. The first four serial devices will be manufactured at SMA's as well. The remaining 48 serial devices will subsequently be produced by the joint venture in Wujin.

Enquiry No 31A

SMA Regelsysteme GmbH is based in Niestetal, Germany. www.SMA.de