Understanding three phase.

[Rampage]

I've heard many a time on here that people don't understand three phase enough to work on it.
Im just wondering what exactly people don't understand?

 

[Bobster]

Just allows smaller components in the rectifier to be used, the loads split across six instead of just three.

 

[Knobhead]

There's no need for smoothing with them, the electrodes and plates act as a giant capacitor. That is until the crap builds up that much and the damn thing shorts out. Thats when it's time to get in there and eat dust.

 

[Bobster]

There's no need for smoothing with them, the electrodes and plates act as a giant capacitor. That is until the crap builds up that much and the damn thing shorts out. Thats when it's time to get in there and eat dust.

Why I've been in one today, one of the banks was sparking over a lot more than they normally should. Water had got in through one of the pots and cause dust to clag up over the insulator. It's the nature of the beast for them to short out when the dust content gets exceptionally high or moisture is introduced. Although a 350degC running temp helps keep it out.

 

[Rockingit]

I can't talk about industrial machinery, nor HV/MV. I'm not going to pretend to be E54's muse when seeking inspiration on some massive construction project either. I remember sitting in college many years ago learning the theory, I can follow and join in a discussion (to a point) and I can always go and make the tea when out of my depth.

That's what makes me 'competent'. To know when you're out of your depth and to seek help.

However, on the other Fleming, I've spent most of my working life lugging 400A camlocks from one side of a wet muddy field to the other, connecting generators together so that they don't fight, and making damn sure that the fuse won't blow - ever. One user makes LOADS of interference and massive imbalances, another wants an almost DC pure line and clinical earth. One user uses delta, another just wants it star > 3 x 1ph. So do I know 3ph? Yes, I do. Each to their own, and as I've said on this forum time and again, we ALL have specialist skills and sub-sets. That's what makes this industry so exciting - there's ALWAYS more to know if you can be 4rsed to.

 

[ian.settle1]

I can always go and make the tea when out of my depth.

That's what makes me 'competent'.

Thats what I like a good can lad that knows his place:rofl::hurray:

 

[Knobhead]

RoB2, this might surprise you as to how inefficient those rectifiers are.

This is the full 6 phase sine wave

View attachment 14369
Now rectified
View attachment 14370

Leaving us with just this little ripple on the top doing the useful work.
View attachment 14371

They also knock the stuffing out of the windings meaning they have to have stronger internal bracing.
That being said they are the cheapest way of producing the 100KV needed for a precipitator.

 

[HandySparks]

RoB2, this might surprise you as to how inefficient those rectifiers are.

Leaving us with just this little ripple on the top doing the useful work.
View attachment 14371

er, maybe I have the wrong end of the stick, but if what you're after is DC, then surely the less ripple the better?

 

[Knobhead]

You are, but a lot of the waveform doesn't get used.

This would have been a better way of showing it

View attachment 14374

As you can see until the sine wave voltage reaches the base of the ripple it doesnt get used