Transfer Switch between Three Sources

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DanS26

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Location
IN
I have a friend that runs a charter boat business. On the boat are two diesel generators. During a charter he runs the generators so that they get equal use. When he docks the boat he uses shore power.

Now here is the problem. Whenever he switches between power sources he uses a manual process involving a lockout disconnect switch between the three sources. The process works well except there is a momentary blackout on the boat during the switching process. This is disconcerting to his customers since the boat goes into blackout for a few seconds. Clocks lose their time and electronic devices automatically reboot. Not a good thing when you are trying to provide a high end experience.

I'd like to install an ATS system which would switch power sources in micro-seconds instead of the manual system. Three different power sources switched electronically. Is this possible?
 

JFletcher

Senior Member
Location
Williamsburg, VA
Yes, it is possible. I used to work at a waste water plant which used 2 16cyl Caterpillar gensets for back up power. The gensets synched to each other, then picked up the loads from the POCO via a synchronizer switch. This provides uninterrupted power going from POCO---> internal power and back. Another plant used one 20cyl GE710 with a manual synchronizer to do the same. You cannot operate the switch unless the utility and internal power waveforms are aligned perfectly. As to what equipment you'd need to accomplish this, Ive no idea. Probably pretty pricey, would be a lot cheaper to put e-lights where needed and a PA to announce transfer of power.
 

GoldDigger

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Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
Another alternative is to put a UPS on the output of the manual transfer switch. It does not have to have a large storage capacity since it would only have to carry the load for a short time.
A full time (dual conversion) UPS would provide completely uninterrupted power and would stabilize the voltage and frequency across the various sources.
 

ron

Senior Member
For this size generator, it is unlikely he can handle the paralleling of the two generators before closed transition.

Maybe run one generator one day and the other generator the next and alternate that way. Then they get equal run time and no issues messing around with generator controllers.
 

DanS26

Member
Location
IN
Thanks guys for the comments. I sort of suspected a three way ATS was not really feasible.

I think I'll recommend an ATS between the two diesel generators and just keep the manual transfer process between shore power and rest of system. Shore power transfer is just once a week as opposed to every day between generators.
 

DanS26

Member
Location
IN
A two way ATS is feasible as the duty generator can be pre selected.

Yes this is what I was thinking. I'll place a toggle switch on the N1 utility sense (or duty generator in this case) line. When the toggle is switched the ATS will think the duty generator has gone off line and will switch to the second generator in a micro second. It will of course require both generators to be running. The process is reversed to switch back to the duty generator.

Hardly a a blink in the switchover and all clocks and electronic devices will not notice.
 

Tony S

Senior Member
Yes this is what I was thinking. I'll place a toggle switch on the N1 utility sense (or duty generator in this case) line. When the toggle is switched the ATS will think the duty generator has gone off line and will switch to the second generator in a micro second. It will of course require both generators to be running. The process is reversed to switch back to the duty generator.

Hardly a a blink in the switchover and all clocks and electronic devices will not notice.

Hopefully :?
 

DanS26

Member
Location
IN
Hopefully :?


I have had good experience opening the N1 so that an ATS will switch under load. A high quality ATS with a very fast magnetic switch is needed.

Most people will test their ATS and generator under load by just opening the main breaker. Then go around resetting all the clocks in the house, etc. Opening the N1 or N2 will accomplish the load test without electrical interruption.

I recommend that every six months a generator system be tested under load in addition to non-loaded exercise built into most standby systems.
 
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