Alternator stator output / Balmar MC-612 Tach pulse?

[nigelmercier]

I can't get my brain in gear this morning! This is a long shot, but worth a try...

Does the stator output from an alternator swing positive and negative, or is there a DC component so it is always positive?

What about the Tach output of a Balmar MC-612? Has anyone looked at it on an oscilloscope?

 

[VicS]

I can't get my brain in gear this morning! This is a long shot, but worth a try...

Does the stator output from an alternator swing positive and negative, or is there a DC component so it is always positive?

What about the Tach output of a Balmar MC-612? Has anyone looked at it on an oscilloscope?

It's a 3 phase AC output. I believe some are a "star" and some are "delta" configured

No knowledge of that particular alternator but the tach output is usually a direct connection to one of the stator coils.
The return path must be via the negative half of the rectifier so presumably it is in effect a series of positive half wave pulses.... but my head does not get around this sort of thing too well

 

[Billjratt]

The stator is AC which is rectified by internal diodes (6 in the case of the Balmar, 9 in bosch/lucas etc. usually) The tacho output is simply taken from the raw AC (one of three phases)_ prior to rectification and can also sometimes be used to pick a relay depending on the initial field energising circuit.(because of the three 'missing' field diodes)

 

[cimo]

I can't get my brain in gear this morning! This is a long shot, but worth a try...

Does the stator output from an alternator swing positive and negative, or is there a DC component so it is always positive?

What about the Tach output of a Balmar MC-612? Has anyone looked at it on an oscilloscope?

stator o/p is normally positive & negative - no DC component until after the bridge. Alternator tach o/p is also normally positive & negative - to drive analog tachos - taken directly from one of the stator windings as mentioned. You'll need to know how many poles your alterntor has - and adjust the tachometer to suit (or just guess by trying all settings!).

(no experience of the MC-612 unfortunately. I'm finding it impossible to get any information on valeo alternators. if you come across any, would appreciate a link!)

 

[nigelmercier]

Thanks for the replies.

I've finally got a reply from Balmar. The stator is of course AC, positive and negative going. It seems the Tach output on the MC-612 is just a direct feed of the stator, so will be the same. I'm just waiting to find out the peak to peak voltage ...