GearBox Suggestion Required

The motor rating should be something in excess of the alternator maximum output power to allow for losses in the gearbox, bearings, etc.

The rpm of the motor differs from 275rpm by the gearbox ratio.

hi PWSlack,

Thanks for your reply, was actually looking for more specific details on the type and rating of the gearbox to be used and the ratiing of the driving motor

Is this for conversion of single phase electric energy to three-phase electric energy?

If so, remember that the single phase motor has only one pulse of peak power for every three of the alternator (assuming the input and output frequencies are the same), and must use 'flywheel' energy to get through the other two alternator pulses, regardless of any gearbox. I don't know exactly how this translates in terms of torque, but the single phase motor will require significantly larger peak torque than the alternator peak torque.

If not, then this sounds like a perpetual motion scheme, destined to fail. You will always require more energy to run the motor than the alternator can produce, so there will definitely be a net energy loss. If the purpose is not phase conversion, then you are wasting your time.

Now upon further thought, 275RPM is 4.583... RPS. If you have 11 poles, that will give you an output frequency of 50.4Hz. If you have 12 poles, it will give you an output of 55Hz, and if you have 13 poles, it will give you 59.6Hz. None of these are standard frequencies. What are you trying to do?

How do you have 11 or 13 poles?

Hi all,

The alternator i have manufactured is a Permanent Magnet Alternator with NdFeB Magnets (48 Poles). It produces 3 Phase AC Output. At 275 rpm i get 440V AC between Phase to Phase on No-Load Condition.

The reason i want to run this alternator coupled to a motor with a Gearbox is to conduct a load test on the Alternator.

I was trying to run this assembly using a 40HP, 1440rpm Motor with a 17 Teeth Chain Sprocket and a 90 Teeth Chain Sprocket on the alternator(PMA) shaft, but when i apply the electrical load on the PMA the speed drops drastically from 275 rpm to about 100 rpm

Please note that in the image you see a Pulley and V Belt, but i have later changed to Chain Sprocket as the belt was getting over heated as i applied the load

Your problem is the 40HP motor. 40HP = 29.827994864KW!!!! See post #3. Your test setup should use a 100HP motor, and then the chain would work fine. No transmission will give you 50KW out with < 30KW in. If you find that transmission you have solved the worlds energy crices.

I was just trying to figure out what frequency the thing would put out at 275RPM. With permanent magnets, lots of things are possible. Not necessarily correct, just possible. As you obviously know, an odd number of poles would require two adjacent poles of the same kind.

Now that we know it is for a wind turbine with an inverter, it does not matter what frequency it generates, as it will be rectified anyway.

Extremely sorry for not following up the postings here

The PMA is designed and developed by me for a client who is going to run it connected to a Vertical Axis Wind Turbine.

What i wanted to do was connect this PMA with a Motor using Pulleys and Belts or GearBox and then run the PMA at the design speed of 275 rpm.

I plan to connect Water Immersion Heaters as Electrical load because frequency control is not available while testing.

When i connect the Electrical Load and run the Alternator at 275 rpm, i want to show the actual readings of the voltage and Current which then can be used to calculate the power generated by the PMA 3 phase power = 1.732 x Voltage x Current x Power Fctor (assume as Unity as load is purely resistive)

If you google for "36KW Permanent Magnet Alternator" you will see a youtube video i have uploaded of a 36KW PMA i have designed and manufactured.

Rgds

Girish Iyer

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I may be a bit too negative about this, my apologies and I wish you well, but I see problems that I personally cannot imagine how to fix them......

If you are going to run a closed system for yourself, it could work, if you are thinking of eventually feeding back to the mains, I see major problems ahead.

I will follow this blog with great interest and I hope I am simply too negative and completely wrong........

Hi Andy,

I am planning to finally operate this as a Wind Turbine system and hope to connect to the grid using Grid Tie Inverter.

Could you please elaborate what your mean by "if you are going to run a closed system for yourself, it could work"

Please find Pics of the Turbine and the Alternator during manufacturing of the PMA which is already installed and running

By the looks of it your rig is quite reasonable for the testing you are doing.

Perhaps you just applied too much 'electrical load'

By the looks of the turbine you won't get to your alternator rating.

But it does not matter if such a turbine is 'over alternated' - it will only make what the wind provides anyway.

If the gearbox is for the final installation (not test bench work) - you may find direct drive of the alternator and say 240 V across phases (lesser rpm) is a more efficient proposition.

Wow, nice rig! You built that?

I would use a small car automatic transmission stuck in "low" if I was McGyvering it. Run the engine, drive the alternator, test the system. Then I would use a similar torque converter between the turbine and the alternator in the final drive assembly if the engine test came out ok.

If you are going to attach to the grid, you need to "parallel" your generator.

What voltage does your generator produce at the frequency of where you are (I believe that detail has not been mentioned yet!), when unloaded?

To parallel, you need to have a slightly higher voltage and be of a slightly faster frequency.

If your voltage is far higher at that frequency than the mains, when you close the final breaker it will "snatch" load. It may even stop momentary if it takes a load greater than the wind blades can supply.....so you will need to have a windmill that produces more torque than you need for running.....and I don't think that there is a way to "control" the voltage as is really needed, or am I missing something that you haven't mentioned yet....

If you have access to a tractor with a PTO, you could make up a connection to the PTO output shaft and adjust the RPM via the tractor motor. With an appropriate size machine you should have plenty of torque.

PTO = ? (Sorry not much familiar with mechanical systems)

PTO=Power Take Off - an extra power output shaft on most industrial/farm tractors used to power accessories.

Thanks buddy