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Delta, star, Jerry riged?
Gary D:
In Jerry's other test (wind truck), he got 1425 watts at 35 volts.... He only had 3 rectifiers rated for 6 amps each per phase, so they would have fried (or been at max. output) at 630 watts. There HAS to be some adding of amps from the other coils since this was close to double their ratings??? This was why I thought going to 10 coils such as hughs 5 phase machine would give a bit more load sharing (coils closer to peak,, not 120 degrees out). My inept way of looking at things. Hope not to offend either viewpoint, just think Jerry is on to something! Wonder if increasing the lathe test rpm a bit to get beyond the amp rating of one rectifier might clear things up? If a 6 amp rectifier should blow at x speed single phase, exceed that speed by a bit. Hook 3- 6 amp rectifires( one per phase) and see what the output is, smoke or more than the 6 amps therorectically possible.... I tend to think increased amps.... Simple quick belt change might clear things up perhaps? Gary D.
DanB:
"If you'll connect them after
the rectifiers
(the way of Jerry and Hugh), ...."
Actually Hugh is using a conventional 'star' connection, but two coils are running in parallel, so there are 10 leads coming out - but the output of any two leads is not through one coil, but through two coils which are out of phase through a start connection, just like any multiphase machine wired in Star.
johnlm:
I tend to agree with Oztules. Effectively Jerry ended up with a three phase machine essentially connected in a Delta type configuration, except he added the phases (in Delta case the lines) after the rectifiers instead of before the rectifiers. Because he used a 12 magnet/9 coil arrangement he indeed has a polyphase (3 ph) machine so in fact at any given point in time there were coils that were not at peak voltage while others were. He increased the number of turns on each coil (as also stated in his discussion above) to offset the lower voltage one gets out of Delta. I think (correct me if Im wrong) Jerry is assuming that all the coils are at peak voltage all the time in his configuration which they cannot be because there are points in time that there is no magnet directly over a given coil. The ones that are not at peak voltage are not contributing full current if any to the summation node after the rectifiers. So the bottom line comes down to what I think Hannu stated and that is: Is it more effecient to add the currents together before the rectifiers or after. In the standard Delta case you have fewer diodes active but running at a higher current. In the Jerry-rig case you have more diodes active at any point in time but running at a lower current so it is probably about a wash on power lost in the diodes.
Also to clarify a point that Gary made, regarding the wind truck test with 1350 W (or whatever it was) and 35 amps overloading 3 bridge rectifiers. I think Jerry has 9 bridge rectifiers on his unit he tested on the truck, with the currents not equally divided up between them at any one point in time, but likely any given rectifier pack was running under 6 A.
John
Jerry:
Yes the circuts i've show above are for the normal 3 phase conections not my diode bridge per coil.
But even with a doide bridge per coil its still a 3 phase alt. There are still 9 coils and 12 magnets so the electrical and physical arangment is still there.
Many newbys have asked questions like...do I conect the start to the end or start to start or end to end or lay my coils this way or that way. All of that has no importance with a bridge per coil it just doesn't matter. Each coil and bridge is its own littel ac to dc power supply with all its dc out put contributing to the alts total output.
The sum of all there power is collect to 1 point. The amount of copper is the same, the amount of magnet is the same. The diferance is how the power is collected from a group of 9 coils and 24 magnets (12 per rotor) Rectify each phase seperatly and the phase diferances are done away with.
Hough has discused this with delta. I think he refures to it as hystrisus isuse or some thing like that. If there are phase isues with delta then there are phase isues with star.
JK TAS Jerry
Jerry:
Hi hiker.
There would be more diode loss if all the rectifiers were wired in sires then the losses would add up but they are wired in perelell. So the total rectifier loss for all 9 is equal to one rectifier loss only.
JK TAS Jerry
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