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I don't know of specific model numbers but they're pretty common from the major manufacturers. Look up "closed transition ATS."

They have a synch-check relay inside them that looks at the phase angle of the generation system and the utility. Since the frequency of the generator is always going to drift some, even very slowly, the phase-angles of each system will eventually overlap, at which point you have no voltage between corresponding phases and it's safe to parallel.

The synch-check also watches the rate-of-change of the voltage between identical phases on the generator and line, and if they're varying too quickly (meaning the generator is too far out-of-synch with the line frequency), the relay will prevent a transition.
 

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I work for ASCO. I can tell you the closed transition switches are more expensive, and don't forget about the grid interconnect agreement. Why do they want closed transition? As long as the motor loads are kept in check, open transition is almost always fine. If they are going to have a bunch of air handlers and large motor loads, you go with delayed transition or closed.

Usually it is hospitals, or major data centers that go closed transition.
 
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