Voltage/Current

[Willbridge]

25Hz locomotives are already 60Hz capable. It is 60Hz locomotives that cannot operate on 25Hz and require a heavier transformer.

The Denver RTD units are pure 25kV and have the lighter 60Hz only transformer unlike the SEPTA ones, which have 25Hz transformers which will incidentally work fine on 60Hz.

Incidentally tapped transformers are more expensive than single voltage output transformers and automatic tap changers are even more expensive. Not things that you buy on limited budgets unless you absolutely need them.

In Denver we had the advantage of starting from scratch and of being the second purchaser of the SEPTA-style cars.

 

[Willbridge]

Appropriate to this thread, a Charles Smalley promotional video for their Milwaukee Road electrification dvd was posted a couple of days ago.

 

[west point]

25Hz locomotives are already 60Hz capable. It is 60Hz locomotives that cannot operate on 25Hz and require a heavier transformer.

That is correct for present Locos on the NEC. But past 25 hZ locos - GG1s, E-44s, & New Haven Jets did not have the transformer - rectifier -Inverters. GG1s had 25 hZ AC traction motors that were geared for various speeds. DC traction loco motors just had transformers and rectifiers for the 25 hZ operations. Usually they had small DC motor - AC Generators for any AC such as radios.

The lighting, heat, HVAC air compressors were all 25 hZ. Not capable of working 60 hZ, Which is the problem of early SEPTA equipment. As I understand it is only the very last few Silver liner models are fully 25/60 capable.

About E-60dc the traction was DC thru the thyristor rectifiers tuned for 25 hZ not 60.. As far as AEM-7s have heard conflicting statements/ The first delivered were AEM-7DCs. There have been unverified reports that the AEM-7 ACs conversions were for use new Haven - BOS but cannot believe that statement. Observers will have to verify that DCs also worked out of BOS.BTW Caltrain's 2 AEM-7s are AC.

 

[BlackDiamond]

Appropriate to this thread, a Charles Smalley promotional video for their Milwaukee Road electrification dvd was posted a couple of days ago.

The "Little Joes" were built for the 3 KV DC electrification used by the Soviet Union at that time, which meant they fit right into the Milwaukee Road system that was also 3 KV. There were some Joes that went to the South Shore which used 1500V DC, I assume the locos could be easily modified to handle this?