Good afternoon all.

Hoping someone can help me with a small problem.I have a RCT 3kw inverter build into my camper.I want to connect a 800w wind turbine to it.Can I connect it to PV input?

@Cape Water Guy,

Yes you can, provided the Output of the turbine matches the Input requirement of the 3kW RCT.

I don't have the 3kW spec handy, but I know on the 5kW model, it is 60V min -145V max.

The wind turbine output is usually 3 phase AC, so you may need to rectify it first. That is usually done at the charge controller so I don't think you can connect directly. I have a spare controller for my 800W turbine, PM if interested.

Edited February 26, 20197 yr by DeepBass9

2 hours ago, Sidewinder said:

@Cape Water Guy,

Yes you can, provided the Output of the turbine matches the Input requirement of the 3kW RCT.

I don't have the 3kW spec handy, but I know on the 5kW model, it is 60V min -145V max.

Thanks

It looks like it must be DC not AC.

SOLAR CHARGER
Maximum PV Array Power: 600 W
MPPT Range @ Operating Voltage: 30VDC ~ 66VDC
Maximum PV Array Open Circuit Voltage: 75 VDC
Maximum Charging Current: 25A
Maximum Efficiency: 98%
Standby Power Consumption: 2 W

5 hours ago, Cape Water Guy said:

It looks like it must be DC not AC.

You do get DC turbines. They have brushes in the back, ie you might say they have "mechanical rectification". They are less popular than the AC kind (that uses slip-rings, like a car alternator) because they have more maintenance. Or so I hear.

Edit: Or maybe they included the rectified bridge in the device. Again, like a car alternator 🙂

Edited February 26, 20197 yr by plonkster

3 phase is useful as it gives you an electromagnetic brake. If you bridge all 3 phases then the turbine works against itself and effectively stops (or turns very slowly).

Edited February 26, 20197 yr by DeepBass9

Just now, DeepBass9 said:

turns very slowly

Now that reminds me of a story I read of bleeding brakes on an old Rolls-Royce. This vehicle had a rather interesting "booster" setup, it used a Friction plate around the drive shaft that in turn actuated the hydraulic master, so when you pressed the brake you transferred torque from the drive shaft to the brake master, or in other words, it uses the car's own movement against it. The story was: How do you bleed this thing? Well, apparently you jack it up and work the cylinder from below... 🙂

Sounds like the brakes on my MF165.

19 minutes ago, DeepBass9 said:

Sounds like the brakes on my MF165.

Isn't that a normal dry friction type setup? I know it's "inboard" inside the rear axle, most likely to keep it dry 🙂

This particular Rolls-Royce had hydraulic brakes, like most other cars, but they used power from the drive shaft to implement "power brakes". Probably because it's a Royce and you shouldn't have to stomp on any brakes 🙂

No, it's a wet story inside the diff. I'm too scared to open it all up and look inside...   Two plates get forced apart by the brake lever somehow apparently.

" Probably because it's a Royce and you shouldn't have to stomp on any brakes "

You wouldn't want to spill your champagne after all...

"

Edited February 26, 20197 yr by DeepBass9

1 hour ago, plonkster said:

You do get DC turbines. They have brushes in the back, ie you might say they have "mechanical rectification". They are less popular than the AC kind (that uses slip-rings, like a car alternator) because they have more maintenance. Or so I hear.

Edit: Or maybe they included the rectified bridge in the device. Again, like a car alternator 🙂

Thanks did test it now and it gives out 24v AC.Ordered a 3 phase controller on eBay.

1 hour ago, DeepBass9 said:

3 phase is useful as it gives you an electromagnetic brake. If you bridge all 3 phases then the turbine works against itself and effectively stops (or turns very slowly).

Tried that one.The faster you spin it the harder it is to turn.😂

Remember that AC is RMS volts so 24VAC will convert to 24  x sqrt(2) = 33V DC

34 minutes ago, DeepBass9 said:

Remember that AC is RMS volts so 24VAC will convert to 24  x sqrt(2) = 33V DC

Thanks. I should still be safe with these specs?

Maximum PV Array Open Circuit Voltage: 75 VDC

MPPT Range @ Operating Voltage: 30VDC ~ 66VDC

If you get a 24V controller for the turbine, it will connect straight to your batteries, not through the PV input on your inverter.

Running the output of a wind turbine through a charge controller intended for PV use will not be productive simply due to the nature of the way MPPT works.

A charge controller designed for WT will allow the user to manually enter the I/V curve data, which may be available from the manufacturer, more often via observation and data gathering.

1 hour ago, DeepBass9 said:

Remember that AC is RMS volts so 24VAC will convert to 24  x sqrt(2) = 33V DC

Also remember it is "wild AC" so it is not fixed-frequency. The frequency will vary with the wind speed. The waveform is sinusoidal though, so normal RMS->peak conversion applies as @DeepBass9 already explained. Multiply the AC voltage by 1.44 essentially.

2 hours ago, DeepBass9 said:

No, it's a wet story inside the diff. I'm too scared to open it all up and look inside...   Two plates get forced apart by the brake lever somehow apparently.

I saw a video about that, you can just google for it. Apparently it is supposed to stay dry. It has two plates (they look a bit like clutch-plates) that are forced against another surface and stopping it via friction.

These things are heavy-duty though. In my 42 years of being alive I don't know that a tractor every needed a brake job. Clutch, yes. Hydraulic pumps, tyres, engine overhauls, and son on, yes. Never brakes. Probably because engine-braking is so effective already 🙂

1 hour ago, DeepBass9 said:

If you get a 24V controller for the turbine, it will connect straight to your batteries, not through the PV input on your inverter.

Ok thanks for that info.

7 hours ago, plonkster said:

The waveform is sinusoidal though, so normal RMS->peak conversion applies as DeepBass9 already explained. Multiply the AC voltage by 1.44 essentially.

When you three-phase rectify (a bridge with 6 diodes) a three phase AC source, you do get close to DC, with a peak value of √2 (1.414) times the phase-to-phase voltage. But there is about 6% ripple (13% peak to peak); that's small enough to be neglected in some situations.

But the power factor has to be terrible. Other than at the instant of phase "commutation", one phase always has zero current (the one phase that isn't the most positive or the most negative at any instant won't have either diode conducting). That can't be the best way to extract power from the wind turbine, and extracting maximum power is what a wind turbine is all about, right? So I would hope that a "real" 3-phase charge controller would actually have three boost converters that work on one of the three pairs of inputs. Each of these would be like the "PFC" stage (Power Factor Correction, but it's a terrible term for what it does), so that the current is nearly sinusoidal. It seems to me that these would have to be isolated from one another, so three high frequency transformers would be needed.

This would seem moderately expensive. The big wind turbine farms would have to do this, I would think, but what about the smaller controllers? A quick web search seems to indicate that they just 3-phase rectify the output, with all the problems that this entails. Does anyone happen to know how it's actually done? Perhaps having current flow 2/3 of the time isn't considered so bad. Even though the current will fall from 86.6% of peak to zero for 120° of the cycle, then step to -86.6% of peak. I saw a paper suggesting that LC filter networks and a single boost converter (for the 6% ripple) can dramatically improve the power factor, so perhaps that's how it's done. But that was for fixed frequency, and high power low-frequency inductors are bulky and expensive, and with the variable frequency... it doesn't seem practical.

As a total off-topic aside, we used to have trams (they would be called light rail these days) in Brisbane, Australia. These worked on nominally 600 VDC. We have 240 VAC power here, so three phase is 240 x √3 = 415 V phase to phase. They used to use mercury arc rectifiers to convert three phase 415 VAC to DC for the trams. 415 x √2 = 587 V, which rounds to 600 VDC. There is a tram museum here where enthusiasts still run a few trams over a short track, and the tour guide gives a history of the trams. There is even a "Who Killed the Electric Tram" side to the story: there was a suspicious depot fire near the end of the tram era, that soon saw the tram tracks ripped up and diesel buses took over. Back to the topic a little: they must not have cared much about power factor back in those days.

I remember the electric buses all over Johannesburg in the early 80s.