Low voltage on my micro hydro turbine

Hello from British Columbia Canada.
Let me introduce myself, l am a retired fellow and in the past few years I have been fortunate to find an off grid cabin and I am working on it to improve it. I have installed a solar array about 3 years ago and it works great for about 8 months of the year. I got a hold of a 3kw 120 volt 60 Hz single phase turbine. The turbine is about 8 years old but was still in its original crate and never installed. The spec rpm for the turbine is 1800 and was confirmed with a meter. The initial test showed the turbine only making ~10 volts and 40Hz.  After cleaning the “copper rings” on the rotor and cleaning the carbon brushes the voltage shot up to 105 volts and 58 Hz. I’m at lost to figure out what could I do to  troubleshoot this unit. The best I could do is a load of about 90 watts anything more the voltage and frequency drop significantly .
I have a 2” and a 1.5” poly pipe joint together at the turbine for the trial. There is approximately 100 feet of head and a flow of 5.4 litre/second or  86 us gallons/minute.
This is a proof of concept to make sure the turbine works properly before I invest timoand money in a larger pipe and/or more vertical head.
Thanks in advance for any advice
Rene

Do you mean you have 2 pipes both going into the turbine or that the 2" reduces to 1.5" at some point?

This calculator suggests that you're getting about a tenth of the power you should be able to extract. Based on about 50% system efficiency, around 900w.

If you do have full flow, then we're looking somewhere else.

I'm assuming there's a big capacitor under the cover on the side of the generator that creates the reactive magnetic force the same as a motor. Can you get a picture under that cover please?

Thanks for the quick response, much appreciated. The cabin is boat access only and I just got back home yesterday and will not go back until sometime in the new year. I don’t have any photos for you at this time. I have two poly pipes coming down the mountain. One 2” and one 1.5” and I temporarily hooked them together to increase the flow. I will definitely do a better job once I figure out what the issue is with the turbine.
Rene

You have to flash the field windings. This happens when a generator sits for long periods of time without rotation. Your low voltage readings are a sure sign this is the problem you are having.

There are various ways this can be done, and Youtube will give you many free ideas you can try that are free. One way for instance is to plug in a drill and then give the drill a crank by hand. The spinning will impart a field flash that will get the field windings to get their exciter fields reenergized. Again a youtube video will give you exact ways to do this without me having used a thousand confusing words to do the same thing.

There is no exact time frame on why this happens. I had a PTO generator that was not used for 10 years and i hooked it up and it worked just fine. Then I did not use it for 2 years and I had to flash the field windings because of low voltage output. Incidentally I could not flash the field with a drill, but my generator was 220 volts at 20 KW, so maybe I needed something bigger to flash the field? Not sure.

If all else, you can get a generator shop to flash the field windings for you.

Just do be careful. It does not take much to overflash the field windings. I once saw a guy on the railroad take out a 850 KW diesel generator by overusing a teeny-tiny 9 volt battery to flash the field windings. It is called "flashing the field" for a reason, it's just a flash not continuously applied voltage to the field windings!!

I don't know much of anything about generators, but I know just enough about electricity to be dangerous. Voltage dropping under load makes me curious how much is a generator problem and how much is the wiring. Have you tested directly at the generator's lugs, with no wiring installed? (I don't know if you need the ground attached for this test or not.) For that matter, how confident are you about how it's grounded, and is there a way to test that? For an electric fence, I'd soak the ground where the ground rod is (for testing). Since you're working with higher power, I don't know if that would help, but it seems unlikely to hurt.

Your field windings need to be flashed.

I also taught it could be a grounding issue. I drove a four foot grounding rod next to the turbine and it didn’t seem to make any difference.
Is there a way to test the ‘voltage regulator’ ?

R Hache wrote:Is there a way to test the ‘voltage regulator’ ?

Probably, but it exceeds my knowledge. By the way, Steve Zoma and I were typing at the same time this morning, so I didn't see his answer until I posted mine. He's also exceeded my knowledge, but with his experience with outdoor equipment, I suspect his idea is worth looking into.

As for the "voltage regulator", I wouldn't know who to look to. Electrician? Small engine mechanic?

I'm slightly suspicious of that yellow handled ball valve. I don't think that's your current problem but I would remove it and isolate using the valves on the feeds in.

Th fact that the frequency drops should eliminate the idea of bad connections. If the wiring is that big a problem and the generator is working properly, it would be losing 900w into that bad connection and you would notice that very quickly!

So we're back to the generator. I'd still like to see inside that cover to see the voltage regulator and the synchronous capacitor. But as the others have said, flashing the fields would be the first step

There was a sad story of a woman from Ohio whose mother had throat cancer and she did end of life care to the sad bitter end. Then she got intense pain in her throat, so knowing it was cancer, she took a handgun and ended the life of her 9 year old daughter, and her own just to be spared the horror of throat cancer for her, and her daughter by way of genetics.

Except she never got tested. She actually had strep throat; something simple penicillin would have cured. She ended the life of her own daughter, and her own simply by overthinking the situation.

One of the basic rules of mechanics is; to check the obvious things first. We call it "It is just a guess unless you test".

The dead give-away here is the low voltage and frequency drop, also called hertz. Magnets lose magnetism when they sit for long periods of time, and since it take electricity to make electricity, the field windings need to be flashed.

My hydro set up is a little different just to combat this problem. It uses 133 volts DC current to excite the magnetic field so we can generate AC electricity.  A MOP (motorized potentiometer) adjusts the DC current so that the ideal AC current is generated especially during start up as it hunts for synchronicity.

But that is your dead giveaway here. Your frequency (hertz) is lagging with your lowered voltage. Since you lack a MOP, you cant match voltage to the rpm to get constant frequency. If you had a faulty governor, or improper inflow, it might give you a low frequency number, but be fairly consistent. Since your low voltage and varying frequency is tied together in this problem, that tells me your field and stator windings are out of sync. Normally I would say, "yes, it is your voltage regulator that went bad", but because it sat for so long in the box, I say with 99.9% certainty your field windings need to be flashed.

Thanks everyone for your insightful comments. Much appreciated.
I will certainly try to ‘Flash’ the turbine on my next trip to the off grid cabin.
I will post an update once done.
Happy season to all.
Rene

I tried to do some research on the internet in regards to the procedure on how to flash the windings on an hydro turbine generator and i don’t think I am getting any relevant information. If someone has a link to show how to proceed I would really appreciate if you could share the links.
Happy holidays to everyone
Rene

Hi Rene
I read your post from months ago. So you may have found your rpm problem.  water need more speed, larger supply pipe . You may have done this. try to run piping with out 90 deg fitting, will slow the speed of the water.
 One note i see on your slip ring the brush has not been seated to the ring. This will create hot spot for all the current to pass through. I recommend to shape the brush to the surface of the slip ring. I tape sand paper to the ring and work the brush back and forth to sand it into shape. use a fine sand paper 150 and polish 220. I hope this is a bit help full. and flashing the winding can help to induce a magnetic field into the gen. have you found how to flash the winding ?

It looks like low voltage and frequency issues with micro hydro turbines can stem from a few key factors. Based on troubleshooting guides and discussions, here are some possible causes and solutions:
🔹 Field Windings May Need Flashing – If the turbine has been sitting unused for years, the exciter fields may have lost their charge. A common fix is to manually "flash" the windings using a drill or another method to re-energize them.
🔹 Pipe Configuration & Flow Rate – The current pipe setup (2” and 1.5” poly pipes) may be limiting water flow. A larger diameter pipe or increased vertical head could improve performance.
🔹 Generator Load & Efficiency – If the turbine struggles beyond 90 watts, it may indicate inefficiencies in the generator or incorrect load balancing. Checking the capacitor under the generator cover could help diagnose the issue.
🔹 Mechanical Wear & Electrical Components – Since the turbine was never installed, some components may need additional cleaning or replacement (e.g., brushes, copper rings, or internal wiring).