If you really want to go all-out, there are companies that make universal shore power converters. They take in whatever you give them, and put out exactly what you want. But they come at a high price in $$, space consumption, heat dissipation, and complexity. If for no other reason, the cost eliminates them as a possibility for me.
The other approach is to use boost/reduce transformers to match up the voltage. This is a much more cost-effective approach, but it only matches voltage, not frequency. 60hz power will remain 60hz, as 50hz will remain 50hz. As a result it's a partial solution, but for me, it will have to be close enough. After all, firing up the generator is always an option to get exactly the power we want. At a minimum, I want to be able to leave the boat in a foreign marina on shore power for extended time while we are away. To do that, the bare minimum is to be able to run the HVAC so the boat doesn't become a Petri dish, keep batteries charged up, and run whatever alarm and monitoring equipment is on the boat. Anything beyond that is icing on the cake.
Given all this, here's what I think we need to be able to handle for shore power, and what it needs to be converted into on board.
- 120/240V 60hz shore -> 120/240V 60hz ship
- 120/208V 60hz shore -> 120/240V 60hz ship
The cases above can be handled with a boost transformer. Several different companies make them, and the transformer used on the N60 can be adapted to do this as well. We have elected to make this feature part of our build so we can run on 208V shore power without stressing any of our electrical appliances.
50hz operation is a lot trickier. Not only is there a voltage difference to deal with, but some 60hz devices can handle 50hz, where others can't. This means that when plugged into 50hz power, we will only be able to run selective devices, and the list is short.
- Hot water heater
- Battery charger
The above appliances will run at 50hz, but there is some fine print involved, including one little tid bit that was completely new to me. The first bit of fine print is on the HVAC components. They warn that when run on 50hz, their output is reduced by 17%. OK, that's not a bad price to pay, and something I can live with. But there is another more subtle part to the fine print. It says they can be run at 200V 50hz. Not 230V, not 240V, but 200V. What's with that? I started hunting around and found this article which explains it in more depth http://www.usmotors.com/TechDocs/ProFacts/Voltage-Frequency-Variation.aspx. The key is that if you reduce the frequency, you need to correspondingly lower the voltage or you risk overheating and burning out the motor. Running the HVAC directly off 230V 50hz would appear to be really bad for the compressors and fans.
The solution to this obscure problem is to apply a voltage REDUCTION when operating at 50hz, intentionally bringing the voltage down to 200V - at least for the HVAC. That will make it happy, and be operating it completely within manufacturers specs.
Although the HVAC wants to see 200V 50hz, the water heater and battery charger will actually be happier with the native 230V 50hz power, so ideally it would be nice to have both.
After a bunch of back and forth with PAE, their transformer manufacturer, and the HVAC manufacturer, we now have both a Boost and Reduce setting on our shore power transformer, and we have added a second transformer on the dedicated HVAC shore power connection so we can independently Boost/Reduce that power source too. Operationally, here's how it works:
Rotary Switch 1 selects which ship's shore power inlet to use:
- 240V FWD
- 240V AFT
- 120V FWD
- 20KW Generator
- Shore (Normal)
- Shore (Boost)
- Shore (Reduce)
- Ship's Power
- HVAC Shore (Normal)
- HVAC Shore (Boost)
- HVAC Shore (Reduce)