Wye netural swich for load control

[hmccoy99]

The approach is to use a wye neutral switch to accomplish the load matching

by swithing from series to parellel this requires the minimal wiring and could be automated easly.

to automate the process I would suggest a little more complex circuit...

 by sensing the current in one of the wye legs  (R1) you can determine when to switch using this sense voltage to control pulse width  modulator circuit to modulate the on time (duty cycle) of a triac. Creating a smooth transitions from series wye to wye to neutral so that there is no stall/spinup oscillation during the transitions phase.  One design consideration is that all the load will be carried by the neutral in the high output mode.

henry

[scottsAI]

Henry,

This will not work to switch par / Y.

Y neutral point is just that. Will be half the voltage of V+, V-.

At any time some voltage is always more negative and more positive, current through diodes is based on the highest voltage, not current. In another post Flux suggested to use Jerry / Y switch. Looks to be the simplest.

Have fun,

Scott.

[hmccoy99]

I cant find jerrys post for y switching what i gather from flux jerry isolated each leg

with its own bridge and parelleled the outputs. I havent found how he series them up.

maybe there is an error in my thinking about the wiring scheem I posted. I have to re think that.

thanks for your comments

cheers

henry

[hmccoy99]

the only parallel scheem I found of jerry's used multi winding that were across from

each other or in some way could be phased together. but my pma has only three windings

any ideas ?

henry

[scottsAI]

Yes, Jerry's scheme each leg (phase) is isolated, connected to it's own full bridge. (Each phase looks single phase)

I thought delta would be better, testing shows more power than delta. Delta requires each phase to be the same, turn errors etc affect performance, not so with Jerry's scheme. (was invented before, Jerry was the most recent to explore its benefits, his name got stuck on it, here only:-)

Flux was suggesting to add a relay to short one end of the coils together to become a star connection. The other end is still connected to the same bridge rectifier which becomes a 3 phase bridge without switching anything on that end. Just that simple, star point. Nice simple parallel to star conversion!

Switching to Star will boost the voltage, make sure the winds are low before switching back to star. Parallel can be switched to any time. If you will be away without some automated switching, leave it in parallel. Might not collect as much energy on low wind days, safer.

Have fun,

Scott.

[Flux]

Scott is right, your scheme will do nothing, the neutral floats at half volts.

You could use the neutral as battery negative with the bridge operating with it as a half wave rectifier but when I tried the performance was poor and the switching is very complicated. Didn't consider it worth any more thoughts.

Flux

[Ungrounded Lightning Rod]

Delta and 3-phase Jerry-rig produce the same (unloaded) output voltage.  The difference is in the current and resistive losses.

At any given moment one of the three windings has the highest induced voltage.  If the waveforms are true sine (or a number of others that add up right) the induced voltages of the other two windings total to this same voltage.

Both Delta and Jerry3 source the same current, and have the same resistive losses, from the high-voltage winding.  The difference is in what happens in the other two.

Delta sources another 50% of the current from the other two windings.  (Voltage the same, series resistance doubled.)  With half the current through twice the resistance the losses are in proportion.

The current sourced by Jerry is more complicated and depends on details of the waveform, the loading, and the instantaneous phase.  During part of the cycle (when most of the voltage in the off-windings is across one of them) Jerry-rig produces a HIGHER current from the off-phase coils, because it only sees one coil's resistive drop, not two.  During other parts (when things are more evenly divided) the sum may be lower, or even zero.  (And this will depend on loading, too.  High enough loading that more than half your voltage is lost in resistive drop in the coils for a delta means the equivalent Jerry rig will still be sourcing current even at the 50/50 voltage split.) Resistive losses for a given current will be half as much as with the off-side of a delta, because they only go through one coil's resistance rather than two.  But because the current is more concentrated into a portion of the waveform and losses go with the square of the current the average efficiency over a cycle will not see all that improvement.

Further, if the waveforms aren't ideal a delta will have circulating currents.  Even with small deviations from ideal waveforms these currents, and the losses from them, can be large.  Jerry rig doesn't have those losses.

So while I would expect more output from delta than jerry for a genny with a near-sine waveform, I wouldn't be able to confirm it without some tough math and some assumptions on operating conditions - and it would be reasonable for Jerry to be close or maybe even do better.  But for the waveform-of-opportunity gennies we build here having Jerry-rig come in significantly ahead is very reasonable.  B-)

[scottsAI]

Thank you Ungrounded Lightning Rod.

Excellent explanation! Helped me one step further.

I buy everything but the 5th paragraph. (I believe you could create a situation were it was, just not the typical explanation.)

6th paragraph was the best. Non-sinusoidal wave forms is the key.

With a real sin wave Delta would win over Jerry.

Delta current is 1.73 times Star. Like you said the other two phases must be additive to make delta work. The wave forms I see here are not a true sin wave. Therefore Jerry is better. Of course the system must be designed correctly for it all to work.

BTW I had simulated Jerry vs Delta, Delta won, could not figure out why system testing showed Jerry working better. Used the wrong wave form!-) Thanks.

Have fun,

Scott.

[hmccoy99]

I am still not convenced the circuit will not work...  will you agree that with the switch open the circuit will work as WYE..

and with the switch closed you are correct the voltage will be half or really .707 of

the voltage ate the wye point and the diode completes the current path for each of the phases for delta.

henry

[scottsAI]

Hmccoy99,

More by accident I noticed your reply.

Yes, we all agree with the switch open the circuit will work as WYE.

Closing the switch will not do anything. The voltage produced by the WYE is higher thus will be the driving force to the DC output voltage. The WYE neutral point is in the middle of the WYE, Rectified DC voltage is +, - relative to this neutral point, voltage is lower so will not contribute anything, thus the "switch diodes" will not conduct any current.

At this point maybe you need to do a simple test, build it up with a Switch and learn for your self! Sometimes you just got to do it to learn. Could try simulating it, not easy on most simulators. Proper 3 phase is not a standard library component for many simulators.

Have fun,

Scott.