With this railway history, I would like to remind you of a little-noticed but extremely important loner for the development of today’s converter vehicles, the Be 4/4 12001. This test vehicle was created between 1970 and 1972 in the main workshop in Yverdon by converting the De 4/4 1685, which was also an exotic vehicle. It was the only De 4/4 to have electrical equipment from MFO with a recuperation brake.
As newcomers to the scene of railway photographers, we begged our way into the main workshop in Yverdon on 11 August 1972. Our destination was the Ae 3/6II 10401, which served as a heating locomotive in the main workshop at the time… Like many photographers, I realise today that what was taken as a by-catch back then was much more important…
The first three pictures in this article were taken under difficult light and space conditions and were taken with a cheap SLR camera from the GDR. I think the historical rarity of the photos nevertheless justifies their publication. In the background an Re 4/4 I being overhauled. Yverdon main workshop, August 11, 1972 Photo: Edi Meier, BülachThe other side of the rebuilt vehicle with partially opened side walls. The devices visible in the front gate are probably electric smoothing throttles, which are essential for converter operation. The bogies in the foreground are similar to a De 4/4 bogie. However, the vehicle stands on its own bogies… As vehicles were already discarded as spare parts donors at this time after the conversion of the De 4/4 1661 – 1671 to steel bodies, they could have come from this source. However, the rivets in the centre of the bogie, which are clearly visible in the photo from Lucerne, are missing and the central cranking is also missing in Lucerne. Perhaps someone can say more about this… Please use the form below.Yverdon main workshop, August 11, 1972 Photo: Edi Meier, BülachA third photo of the vehicle in the main workshop in Yverdon. In the foreground are four parts that remind me of nose bearing drives. Perhaps someone can say more about this… Please use the form below. August 11, 1972 Photo: Edi Meier, Bülach
Converter technology (for those interested)
The Be 4/4 12001 is regarded as the first inverter locomotive with a DC link feed from the overhead contact line. With this test vehicle, BBC engineers gained important insights into converter technology and were among the world’s leading developers of this technology.
Normal thyristors were used, as known from the gating control system. These semiconductors are switched on with an ignition pulse and remain conductive until the sinusoidal AC voltage crosses zero.
For inverter operation, it should be possible to switch the thyristors off again at any time. This was achieved with an additional circuit, known as a quenching circuit, with which the current could be reduced to almost zero (holding current). This meant that they were and remained effectively switched off until the next ignition pulse.
The next vehicles were also built with this technology: Am 6/6 18521 -18526 (but diesel engine and generator for feeding the intermediate circuit) and Ee 6/6 II 16811 – 16820.
Semiconductor technology was further developed for the converter application: the GTO (gate turn off) was created, which can also be switched off again with a pulse. GTOs were used for the first time in the Re 4/4 of the BT, SZU and EBT, so one could speak of 2nd generation inverter technology.
Today, other semiconductors are used again, so-called IGBTs.
As Be 4/4 12001, the vehicle was in scheduled service in the Seetal, alternating with the normal De 4/4 1661 – 1668. Here, Be 4/4 12001 is standing in Lenzburg in front of train 2246 Brugg – Wildegg – Lenzburg – Lucerne. Behind the locomotive you can see a type ABD(i?) coach, which was originally built as a trailer for the Red Arrows. Date unknown; photo: Werner Hardmeier, RümlangThe Be 4/4 12001 ready for departure at the head of a Seetal train, again with ABD(i?). These coaches were probably mostly combined with the Be 4/4 12001, as unlike the De 4/4 1661 – 1668, the Be 4/4 12001 did not have a luggage compartment. The green non-smoking compartment in a standard coach II on the neighbouring track is clearly visible. Date unknown; photo: Werner Hardmeier, RümlangHowever, the Be 4/4 12001 was not particularly popular with the engine drivers because of the different operation, the poorer visibility and because it occasionally caused the thyristors to blow. This protective function for the expensive power semiconductors is triggered in the event of a fault and leads to a violent jerk. Be 4/4 12001 in front of the Lucerne depot 30.07.1977 Photo: Edi Meier, BülachThe vehicle suffered damage to its electrical equipment in 1975 and was put in storage until its demolition in 1981. If I remember correctly, the vehicle was kept for so long because it was unclear whether it would be used again as a test vehicle for the 2nd generation inverter technology with GTO. The photo of the already garaged Be 4/4 12001 was taken in front of the Lucerne depot after it had been towed out of the depot and had the pantograph on the contact wire for show thanks to external compressed air. 30.07.1977 Photo: Edi Meier, Bülach
For comments and additions to this railway history, please contact our Vice President Edi Meier. Thank you for your help.
