Roto Phase As Generator To Create off Grid Power

You can't use a rotophase for that purpose. A rotophase takes 1 phase power and uses a capacitor plus the motor rotating field to create a pseudo 3rd phase. But it is not a generator/alternator all by itself. At best, the 3 phase motor inside of the rotophase could be theoretically made into a 3 phase alternator, but that is really a difficult project for a novice. The problem is, a 3 phase motor cannot "self excite" to become an alternator, it needs to be connected to a source of excitation power, and that is usually the grid itself. There are tricks to using capacitors and residual magnetism inside of the motor frame to allow self excitation, but that is where the tricky part comes in. You can waste a lot of time and money trying to do it and get nothing for it if you don't know what you are doing. There are articles available on the web in some of the Alt Power forums if you search. They can give you some insight as to the possibility. But to be quite hnest, the practicality of doing that for 2 x 200A services is way beyond what most people would want to tackle.

You are better off buying a true AC synchronous alternator that can be excited from an expernal DC source such as batteries in order to begin generating power. Speed regulation on an auto angine is anther issue needing a lot of attention, but that is not something I know much about. I justknow it's difficult. When you see people use car engines for generation, they typically use DC generators because speed regulation isn't as critical. Then you can hook up an inverter to give you AC power.

You seem to be a novice, so my advice is to start with reading up on off-grid power systems, especially the parts about sizing and capacity. You cannot just say "...230 single phase service at their 2 200 amp 40 switch panels" and have that mean anything useful. You must first do a very thorough and careful load assessment, along with some serious sould searching on your client's part as to which loads he really needs. Running a gas powered car engine to spin an alternator is an extremely expensive endeavour in the long run.

Good luck with that.

Its not that I want to throw cold water on a hot fire but what you are trying to do is not that simple, and will wind up spending more time on something that probably won't work. Unless you spend more money than you want to and only then would you find you have a system impossible to maintain and expensive to fix.

First observation:

You were on the right track when you were asking what the engine rpm should be. You are going to need a governor to apply power. Since this is a "one off" design you are probably going to have to have someone design or monkey up a make shift one. Since it is one of a kind it is not going to work right the first time, and it may or may not ever work in a pratical situation.

Second observation:

On site fossil fuel type generators are always more expensive to operate per KWH than practically any other source of power.

Third observation:

How are you going to transfer the power?

In conclusion, many people have great ideas and sometimes there is new technology developed that may make that idea work out. But normally, if there are any good cheap ideas that gererate power. Someone has already slapped a patent on it and is making themselves a good living off of it.