Voltage drop problems

[John Mantheakis]

I have designed a Poncelet floating hydro generator and will be using the Windtura 750 alternator. Our camp is located in North Tanzania near Lake Natron.
I am thinking of using 3 phase step up transformer to overcome the voltage drop issue since the battery bank and inverter are 100 metres from the floating micro hydro unit.
At the inverter room I plan to use a step down transformer.
Can anyone advise me on this?
Due ro the long run if I cannot use some method of stepping up the voltage then the wire gauge will have to be around 80 square mm. This will mean the expense will be prohibitive, especially since the alternator produces 3 phases thus 3 wires will be needed.
Any ideas?

[Rob Beckers]

Hi John,

Using a set of transformers has been done before for wind turbines (for the same reason). It's been a really long time since I looked into this, and I don't have the equations handy. If I recall, the issue is with iron losses and winding losses vs. frequency: As the frequency gets lower you need massive amounts of core and copper to get decent transformer efficiency. So, one thing to look for is to keep the frequency within a reasonable range.

Hopefully someone else here has more info to help you along!

P.S. would be really interesting if you could post some pictures!

-RoB-

[John Mantheakis]

Hi Rob,
I was in the camp (only radio comms available) so this for my tardy response. I was wondering what others who employ hydro or wind do to solve voltage drop due to long wire runs.
I can only think of step up and step down transformers as a solution. However I am wary of diving in before making sure that this solution will work as our camp is situated 2 days driving distance in a remote area.
Thank you for your response.

[Andy Rhody]

since the battery bank and inverter are 100 metres from the floating micro hydro unit.


I've thought about this because I have also have a cabin with Hydro potential that is about 100 meters from my cabin.

The problem:

Running 12 volts of the windtura (low voltage) 100 meters or whatever.

Possible Solution:

Why not mount everything. The hydro alternator, rectifier, controller, dump load (if needed), batteries, and inverter, all at the generating source. Then you now would be running 120 volts AC.

Question:

Could that 120 volts AC run a reasonable sized cable 100 meters to supply a cabin.

[John Mantheakis]

Andy,

This is not feasable as the river is in a canyon and is prone to severe flooding. Also the inverter is running from an 8 battery bank coupled with solar panels. We use 230v here. The only way I see is to do what utility companies do; using step up/down transformers. If I can step up to 230v at the source then a run of 4 square mm cables will suffice. I can then step down to the source voltage at the inverter room.

[Bruno Motta]

hallo
I did this job for a pelton over 500 meters away using small section recovery cables (maximum attention to good connections in cable joints)
*
using an elevator transformer to the generator and an equal power at the arrival of the house

to size it, a check must be made at the output of the vacuum generator
*to know what voltage it generates at 60 Hz
suppose you do 10 volts; a trax 3x 10 volt 60 Hz is required and output at discretion, we assume 100 volts
certainly the generator will work on 200-400Hz and the transformer will respond very well, indeed it will increase efficiency
in this case a small size transformer is enough

**since the losses are around 3 watts per kg of laminations
at the entrance of the house I suggest to reduce the three-phase voltage, on the 100 volts maximum and use a solar controller mppt to charge the battery bank
24 volt buffer, followed by an inverter according to requirements
bye