AEM-7 status

The AEM-7 AC does fairly well in the heat. As long as the compressor oil coolers under the loco are kept powerwashed once a week and the glycol is kept topped off they run decent in warm weather. The DC motors usually didnt mix well with heat. the ACs were modified with an additional air vent system on the roof that the DCs were not, which is why the dynamic grids are scattered on the roof of the AC.

STrRedWolf wrote:I'm kinda wondering now why all three are operational. Short of filling in for a HHP-8 while that's testing the MARC IV cars, I would think they'd get into more trouble, not less, in the summer months.

As AM stated, remans perform better in the heat than the DCs and the HHP-s. An HHP-8 tanked out Thursday, which is why the protect unit was pressed into service.

I just wonder when the MARC lease expires.

I'm assuming that what's left for MARC service is running on the AC powered AEM-7's. Huh, hope the specs on the Chargers give it more cooling, because Maryland's got some wacky weather.

amtrakhogger wrote:The 942 was running today (in Marc service.) Also the 946 and 917 were spotted in WUT coupled to trains.

shes got some pretty new numberboards from what I saw in a cruddy picture.

An article on the farewell

The AEM-7s made a long-lasting mark on the passenger railroad industry. The AEM-7 logged more than two hundred and twenty million miles on the rails. For bragging rights, the AEM-7 had two nicknames. The AEM-7 was referred to as the "meatball" and the "toaster". The AEM-7 will be formally replaced by the ACS-64 electric locomotive.

Technically, there will be AEM-7s plying the NEC after June 18th.

Ugh and whoever wrote this as no idea what IGBTs are. They are not a cooling system lol.

It's the Examiner. Not exactly top tier journalism...

(Their Fukushima coverage would have been hilariously bad if folks didn't take it as the gospel.)

ApproachMedium wrote:Ugh and whoever wrote this as no idea what IGBTs are. They are not a cooling system lol.

Guess sometimes even a quick Wikipedia research jaunt would go a long way

Looks like they mashed the fact the IGBT's are watercooled.

David Benton wrote:Looks like they mashed the fact the IGBT's are watercooled.

But they dont have to be. GTOs in the HHP and ALP46 are watercooled, the Arrow 3s i think are air cooled gto. IGBT systems can be air cooled depending on use. The level of complication in the thyristor systems in the DCs required oil cooling only because there was about 500 places the oil leaked from and could end up directly in components shorting them out lol.

If you still doubt 917 is running, its pulling MARC 406 right now. I know, because I'm on it.

Nothing say a semiconductor or tube must be air or liquid cooled. It's all a function of how much heat you need to remove and how tightly you're packaged. Most industrial inverters are air cooled, even at power levels that'll make an AEM-7 blush.

The Pioneer IIIs used water cooled ignitrons, the Silverliners were air blast cooled. Air blast cooling had an edge there, though, because of the outside of the tube being at weird potentials (kinda like those old metal cone CRTs of the 50's).

I would think IGBTs would lend themselves better to air cooling because on some level, they should generate a bit less heat.

I'm guessing ASEA went oil cooling on the AEM-7s because oil's a good electrical insulator and somewhat inert. I know the Pioneers IIIs had standards on the water quality to keep them from eating up components...

The problem with air cooling is you need enough room to move the air to air cool. Most locomotives do not warrant this. Plus they are moving and then not moving and loads are varying constantly. So watercooling with a heat exchanger to air is usually best. The same hardware used in a lower HP application will air cool just fine without the water. But trust me, in the small package of the AEM-7 they most def need the water to help!

I'm kinda surprised that anything fits into an AEM-7's body. I'm sure there an interesting story as to why ASEA made the RC series so tiny, but I sure don't know what it is.

Out of morbid curiosity, you wouldn't know much about the HEP inverters on the AEM-7s pre-rebuild? I'm curious what the semiconductor technology and general design is. I swear that you could see a good 25Hz component riding on the lights when the train switched over coming down from north of NYC, which suggests lack of a DC link, but I'm not sure. I've not done any serious digging around to find anything on it online, though..