Induction hydro 1HP

[dbcollen]

I just hauled the 1 Hp 6 pole induction hydro down to the end of the penstock, and hooked it up. Installed a 7/16 nozzle with 100psi  dynamic head(55gpm) I wired the motor for 230vac and opened the nozzle. After a few changes in Caps I got a steady 949 watts into the batteries (17.1A @ 55.5Vdc) with 11uf in delta running 210vac @ 110hz (2200 + slip rpm) 949 watts is 1.27 Hp, there is 3.1 Hp available, so it is running at 41% efficiency water to wire. the motor is running pretty warm, but not hot, I can keep my hand on it.

One thing that I find interesting is the VARs from the caps.

If I put my clamp meter on the power transmission lines it reads 4.17A on each line.

If I put the clamp meter on the leads to the caps it reads 2.86A on each line.

If I put the clamp on the transformer input leads, it reads 2.81A on each line.

The caps are at the transformers up at the house, in delta across the the 3 lines. I havn't tried putting the caps in the Star point at the motor on these turbines yet. I have had good luck with that on other turbines in the past, it usually takes smaller caps, the downside is the caps are at the turbine and need to be protected from the elements.

I was getting 820 watts from the 3hp 4 pole induction motor that was there, same runner (4.72 in pitch dia) Same nozzle. The best power I got was 820 watts with 8uf in delta across the lines. 210vac @ 65Hz (1950 + slip Rpm)

A few weeks ago I had the 20A hydro Breaker trip on the DC side and the turbine ran unloaded with the caps on, I had the bright idea of checking the voltage and my good clamp meter read 1200 Vac for about 2 seconds before it exploded in my hand. The 660vac caps survived, and the transformers and motor got one heck of a Hi-Pot test. The transformer ratio is about 5.5:1 so the 1000 volt rectifier only saw 220 Vac, but the DC breaker had to break 310Vdc (although it probably took half a second to spool up to full voltage) I since replaced the 20A with a 90A.

Dustin

[dbcollen]

Another strange thing about this induction setup is the power increases with battery voltage increase. This would normally be easy to explain as the turbine is running faster with the higher voltage, but this is not the case. As the voltage increases the frequency decreases, so as the voltage goes up the RPM goes down. The only thing I can think to explain this is: As the voltage goes down, the capacitors get less effective at providing the field, and as the field decreases, the RPM increases.

Dustin

[Flux]

Yes the magnetising current will be higher at higher frequencies, running slower will need more capacitance for the same load.

It is very much a balancing act to get everything optimum. Aim to get the turbine speed correct and if the motor speed comes out higher than nominal it doesn't matter much except that it will need less capacitance and a higher ratio transformer. The voltage can be a bit higher if it runs faster. You need enough capacitance to keep it excited but no more than that, if you excite it too hard you will force the core into saturation and increase losses. Ideally you should have the capacitors on the motor end otherwise your exciting current is being supplied via the line and you will increase the line loss, you want to keep the magnetising current local.

I suspect your efficiency is typical, I somehow suspect that you will not get the 80% plus that is possible into resistive loads. Even the axial pmgs suffer with rectifier loads into batteries.

Flux

[dbcollen]

I can get it to excite with (3) 5uf in star (2.5uf phase-phase) but it doesn't deliver much power. (3) 11uf in delta (16.5uf phase-phase) gives the best performance so far, slightly better than (3 8uf in delta (12uf phase-phase)

Dustin

[hydrosun]

It seems that your rpm might be a bit slow for maximum power. I just looked up a hydro chart that shows a 4.5 inch pelton running at 2900 rpm at full load. Your transformers  ratio may be what is limiting more power.

Chris

[dbcollen]

I have been doing experimentation with the induction for 3 years now, and the one thing I have found is they do not react as one would expect. Transformer ratio does not affect RPM as you would expect, only line voltage. The caps seem to affect rpm, (adding or removing field)

Dustin

[Flux]

If the motor is intended for 230v ac and you are running at 110 Hz you ought to be loading it at nearer 400V. I think you are probably running beyond pull out on the curve.

High pole count motors don't make very good SEIGs, you would probably get better results with a 2 pole machine. At 110 Hz I suspect the core loss is starting to rise as well. Having to excite hard and with more iron loss it probably is running rather warm and this loss has to come from somewhere.

Flux

[Ungrounded Lightning Rod]

Another strange thing about this induction setup is the power increases with battery voltage increase.

Not strange at all.  When your batteries are lower they start pulling current at a lower voltage part of the waveform and steal more of the excitation power.

[Ungrounded Lightning Rod]

The caps are at the transformers up at the house, in delta across the the 3 lines. I haven't tried putting the caps ... at the motor on these turbines yet.

You should get a bunch more excitation if you just move the caps out to the motor.  The caps and the motor throw the excitation power back-and-forth through the wiring between them twice per cycle.  You're taking line loss with every toss, so four times per cycle you throw away part of your excitation power to heat the transmission lines.  Move the caps out to the motor and you don't do that.  (That's why power companies scatter capacitors around the grid rather than centralizing them at the generation plants.)

Also:  Lost excitation power is REAL power made up with real HP on the shaft.  (Another reason power companies decentralize their caps.)  Why throw that away?  In addition to raising the excitation, putting the caps at the motor should raise your efficiency a bunch.

I haven't tried putting the caps in the Star point at the motor ...

Were you planning to change the configuration as well as moving them to the motor?

[Ungrounded Lightning Rod]

(That's why power companies scatter capacitors around the grid rather than centralizing them at the generation plants.)

Of course the caps in the power companies' case are to play reactive-power handball with the LOAD, not the GENERATOR.  Which is why you should put your caps near the jenny and they put theirs near the loads.

[Wags]

Don't want to hijack a thread, but it seems you guy's would probably be the ones to advise me on something I have been thinking about.

I am planing to build an induction wind generator similar to a breezy 5.5 or 10k. In their plans they have a capacitor bank located in the main panel conecting two legs of the 3 phase motor. My question is, can I relocate these up to the turbine, so as to open up a circuit on the slipring for another purpose. If I can, would the anticipated life expectancy of these capicitors be long enough for this to be a wise descision.

Thank You in advance for any advice on this, the information available on this forum is unreal.

Thanks

Jeff

[hydrosun]

Doesn't the transformer ratio affect the line voltage? I know there is a lot about induction generators that I have no experience with.

When I was asking  about the rpm of the turbine I was concerned with the efficient transfer of mechanical power from the water to the pelton wheel. I know that the entire system components determines the maximum power point. Compromising on turbine rpm may in this case cause less losses than other components. On Dc generators it seems to be the key to efficiency. Just curious if it is different on induction systems.

Chris

[dbcollen]

I have in the past put the caps in delta as the star point at the motor with good success. I have considered trying that with this one as well. I really like having the caps up the hill, because I can disconnect them and shut off the power, the turbine just freewheels @ 4400rpm. The only way to do that with the caps at the turbine is to crowbar the 3ph and steal the field (real hard on brkrs) I try not to let it run very long unloaded, but it saves me two trips to the turbine when I want to change the taps on the transformers.

I  had the transformers wired series star on the primary, and (2)series (2) parallel star on the secondary with 11uf in delta as excitement. getting 950 watts, I just changed the secondary to (2) series (2) parallel delta which brought the turbine voltage up to 330vac from 190vac, reduced the caps to 5uf in delta and got the power up to 1070 Watts. (46% overall efficiency) running 120hz now

Not bad for a 1hp 6 pole induction motor.

I could never get the 4 pole premium efficiency 3hp over 850 watts.

Dustin

[dbcollen]

A good pelton runner is fairly efficient between 35% and 65% of jet velocity, with the best efficiency at around 50%. running a little fast or slow doesn't affect output much. (I am running 44% Vjet at 120hz)

Dustin