Rotational direction of PMG head

[Randybee1]

Hey guys, I have a friend with a PMG head from Tom Osborne. The directions say that the PMG pulley/shaft must rotate clockwise (as looking at it). Does this make sense? I thought a gen head could spin in either direction.

[BruceM]

It's a major design effort to get something looking like  a sine wave at acceptable voltage out of a PMG over a wide range of loads.
It's no surprise that the mechanical design of the PM rotor  isn't perfectly symmetrical and has a fixed direction of rotation.

[Thob]

Some generators have a fan designed for a certain direction of rotation, which wastes less power than a bi-direction fan.  I don't about this particular design, but it certainly is approaching the level of efficiency where every last fraction counts.

[mobile_bob]

pole shoes on wound field machines often have a leading edge that is a bit wider than the trailing edge, this has affect on the wave form as Bruce alluded to.

i am not sure about pm fields, but it stands to reason that maybe they too are shaped to have a similar characteristic.. if so they yes the thing will be directional to get  the best performance from that head.

between that possibility and the fan direction that Thob alludes to, would be enough for me to want to set the unit up to turn in the direction the oem calls for.   while it probably will generate in the opposite direction it will probably have a dirtier waveform, or make less power, or run hotter, all/some/part of the three?

interesting that they would make a genhead in this way, because i would think that having it be bidirectional would open more sales?  but then again maybe that direction is the prevalent direction called for with their markets, if that is the case, then it stands to reason they would optimize for that direction of rotation.

interesting
bob g

[SteveU.]

Hi Guys
In wound DC generators and motors I was taught that is was the rotational counter magnetic effect that double S shape distorted the magnetic fields. Biasing leading the field magnets hepled to overcome this. Most brushed atmature equipment thia lead is built into the brush holder positioning. Bored/intersted early-on w-a-y back when I slotted some with screwedin brushholders to make then biasable both directtions across centered. Made about a 10-15% difference in power or torque produced over just centered. Once biased optimal for that particular unit that would make it 20-30% WORSE if set up and forced  to counter rotate. Tthe starters having permenet magnetic field case magnets you can even visually see this biasing. Bi-directional winch motors not - centered.
Same thing with fan blade pitching.

If this floats better for you - most boat hulls are optimized go a lot better cutting through thier pushed up bow wave much better forwards than backwards.

Once those "radial" tires take an internal wave directional set for thier own rolling standing wave you can oftern have problems  cross rotating and forcing them to deal with this in the other direction. Cross rotating a couple of tires on a used unknown venhicle can often smooth things right out and get rid of drift pulling.

One size fits all hats fit most poorly.

Regards
Steve Unruh

[Randybee1]

Thanks for all the input guys. My friend has requested membership to join this site and is just waiting....
Randy B