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AC current in 3-phase bridge rectifer

AC current in 3-phase bridge rectifer

AC current in 3-phase bridge rectifer

(OP)
I know the ratio of Vdc to Vac (line) in a 3 phase bridge rectifier is about 1.3 but have forgotten the ratio of Idc to Iac (line) ? Any help ?

Muthu
www.edison.co.in

RE: AC current in 3-phase bridge rectifer

(OP)
I vaguely remember it (Idc/Iac) as 1.732 (sqrt of 3). Am I right ?

Muthu
www.edison.co.in

RE: AC current in 3-phase bridge rectifer

You can use Iac = .817*Idc if your load is inductive (field winding etc). For capacitive loads, you need to look at conducting angles and such.

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: AC current in 3-phase bridge rectifer

I didn't see your assumption. And I am glad I didn't  winky smile

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: AC current in 3-phase bridge rectifer

(OP)
Thanks Gunnar. Yes, it is for an ac exciter with rotating rectifier for a generator field. That AC/DC current ratio of 0.817 seems a bit high, isn't it ?

Muthu
www.edison.co.in

RE: AC current in 3-phase bridge rectifer

Took it from back of head. I think it is right, shall check. BRB.

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: AC current in 3-phase bridge rectifer

Seems to be correct. I checked DC out and AC in for several rectifiers with continuous current.  A few examples:

In   Out   Ratio
35   29    .83
82  100    .82
466 570    .82

I could use an hour or two to derive the analythical expression, but you will owe me a beer for that.
 

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: AC current in 3-phase bridge rectifer

(OP)
LOL. I think I'll take your practical wisdom over math.

IIRR (sigh, I am getting old), I do owe you a beer for an earlier dc machine thread. Whenever you cross the ocean to my side, it will be my pleasure to treat you to one ... or two. :)

Muthu
www.edison.co.in

RE: AC current in 3-phase bridge rectifer

Been thinking about that. Whenever there is an 'exotic' problem with a paper machine, I will go there. You and Arun far away?

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: AC current in 3-phase bridge rectifer

(OP)
I think Arun lives in the beer capital of India, Bangalore and I am at Chennai. Just a 40 minute plane hop away. Just let me know if you do get some exotic paper machine issues around these parts. We will let Arun choose the beer (and probably pay for it too). :)

Muthu
www.edison.co.in

RE: AC current in 3-phase bridge rectifer

Agree! Arun prefers Kingfisher, I think. Please don't tell him. This will be aour secret!

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: AC current in 3-phase bridge rectifer

Hi,
 .817 is for a 6 element rectifier and .578 is for a 3 element rectifier.

Thanks

RE: AC current in 3-phase bridge rectifer

Thanks starkopete. I was about to do some math, I don't think I will do it now.

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

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