Tom, I've seen newer units like that. They also switch between 60hz AND 400hz.
You're talking about the AMMPS (Advanced Mobile Medium Power Sources). I actually saw a couple of these go through GL recently. They are stated as being 2004 models. The AMMPS didn't hit production until like 2008 thought, so they may have actually been prototypes.
The AMMPS are inverter generators, which is how they change frequency. They also can vary their speed to match load, so that they are more fuel efficient and quiet. I would love to have a 5KW AMMPS I think it will be 20 years or more before we see any volume of these being surplused. I don't know if I want a 20 year or more old genset with that much electronics on it. I don't think they'll be as robust in their old age as the venerable MEP-002a and MEP-003a that are so loved by members here.
For more information on AMMPS see:
USAASC - Army AL&T Online
An excerpt from the article:
AMMPS Capabilities
The new AMMPS fleet of generators will be smaller and lighter, as well as have markedly increased reliability and maintainability. The AMMPS sets are required to increase the meantime between essential function failure across the generator fleet from 500-600 hours to 750-1,250 hours and decrease the median repair time from 1.5 hours to 30 minutes.
The AMMPS generator sets will be lighter, more fuel efficient, and quieter than their predecessors and will reduce the logistical requirements on the battlefield.
The new generators will also have an increased fuel efficiency between 15-25 percent. “A more fuel-efficient generator means less time and manpower refueling it in addition to the cost savings achieved from requiring less fuel,” Wallace said. He also mentioned that a recent report prepared by the Defense Science Board Task Force on DOD Energy Strategy states that “during wartime, generators become the largest single fuel consumer on the battlefield. During wartime operations, 357 million gallons of fuel per year are consumed by generators, so even a small increase in fuel efficiency can save millions of dollars per year.”
AMMPS will produce generators in five different sizes: 5, 10, 15, 30, and 60 kilowatts (kWs). Each one will operate in the 50-60 hertz (Hz) frequency range, with some models producing 400 Hz frequency to power radar applications. Overall, there will be 51 different configurations of AMMPS generators between skid-mounted and trailer-mounted applications. Trailer-mounted AMMPS configurations will include power units consisting of one generator on a trailer, and power plants that consist of two generators on a single trailer or two individually trailer-mounted generators that can be paralleled together.
