Bombardier M7 Dual/mode AC/DC aka M8 (proposal)

/*the M2 was built for 11500 volt only and at 60 Hz can take 12 500 as the core saturate sooner with higher frequency.
*/

That's nice. Backwards, but nice.

As the frequency drops, the saturation voltage does too. That's why a 25hz transformer needs to be so much bigger than a 60hz one for a given voltage. The upper limit of the permissable flux is a function of the transformer's construction, the amount of iron, etc. It's fixed for a given transformer. The flux is a function of the input voltage, i.e. it's the integral of the sine wave. Lower frequency = more flux for X voltage. You either drop the voltage or raise the frequency. Thus, for a given transformer, the input voltage goes up with frequency, though this is within limits because at some point the transformer stops working for other reasons.

At X voltage, a transformer that runs at 25hz can generally work at 60hz, but at X voltage, a transformer that runs on 60hz will NOT run on 25hz.

Anyway, the big red book on the M-2 will have the transformer's name plate and photos of it in there, with ratings. The tap switch will be internal to the tranny, BTW - there's only a HV bushing and a ground bushing on the LV side.

You don't want the core to saturate. Bad things happen when it does.

I've built more than a few large machines for export, and we had transformers built to provide 380 VAC, 3 phase, to operate them on. The motor manufacturers told us it was OK to run 50 cycle motors on 60 cycles, but not the other way around, as they would run hot. The transformers we used were export units, dual rated at 50 or 60 cycles.

Of course, the 50 cycle motors ran faster on 60 cycles, but there was nothing short of an expensive MG set or a solid state frequency converter that would have solved that situation.

Since it's unlikely they'll waste the brand new M-8's on Shore Line service, probably they'll reconfigure some M-4's to run on that route. How much would it cost to retrofit these cars (M-4's & M-6's) to switch from 13kv to 25kv on the fly?

The 50-60hz problem is big in Japan. I believe 1/2 the country is still 50 and 1/2 is 60. Interestingly, until after WWII, Los Angeles had 50hz AC.

Aircraft, by the way, use 400hz power. It allows for much smaller and lighter transformers, than 60hz would. This has obvious advantages for aircraft.

It's true the M2, M4 & M6's can run on 25,000 volts. That's why the catenary insolators are rated for 30,000 volts. If you notice there's 3 insolators on each catenary line times 10,000 volts per insolator. 30,000 volts total.

Perhaps with the proposed M-8 EMU, New Jersey Transit may try it out too. They should at least look at it. but they would not do it. Anyway, the M2, M4, and M6 EMUs are getting older, and they need to be replaced.

railfanofewu wrote:Perhaps with the proposed M-8 EMU, New Jersey Transit may try it out too.

Build the M-8's with low platform steps (which might be a good idea for their potential use on Shore Line East, so CDOT doesn't have top build high-level platforms at all it's Shore Line stops), true 25kv functionality (complete with ACCESS cab signaling) and suddenly the design becomes usable up and down the entire East Coast! Both NJ Transit and SEPTA could utilize the car's design for it's EMU fleet (SEPTA's scrapped Silverliner V was supposed to be based on the M-7 design, except with pantographs and low platform steps added -- which would have essentially rendered it the same as the M-8, well, providing the 3rd rail shoes were still present).