Posts: 7
Joined: Thu May 03, 2001 5:05 am

Why Negative Power Indication In Cockpit

Mon Feb 04, 2002 12:30 am

Here I am raising one technical point regarding indication of power in cockpit in Boeing 747-200.
The scale in combined KW & KVAR indicator in F.E. Panel shows power indication upto -20 on the negative side besides normal positive values.
My question is under what circumstances scale will show negative power?
As per my judgement when power is flowing to generator i.e. reverse flow then indicator will show negative power. In that case the generator will act as motor but rotating in same direction. Can anybody explain in more details?

RE: Why Negative Power Indication In Cockpit

Mon Feb 04, 2002 12:38 am

No I think when things are in the negative it shows that you are using more power then you are currently generating. Correct me if I am wrong.
Posts: 1319
Joined: Wed Jul 05, 2000 11:37 am

RE: Why Negative Power Indication In Cockpit

Mon Feb 04, 2002 10:32 am

Indicates how hard the generator is working to produce power. I don't even remember the B747 electrical system, other than that is was split parallel.
Maybe that is a factor. Anyone remember the Classic 47 panels?

Posts: 7
Joined: Thu May 03, 2001 5:05 am

RE: Why Negative Power Indication In Cockpit

Tue Feb 05, 2002 12:17 am

To Mr. lian
There are four generators running in parallel. One generator is showing negative value in a paralleled system means average demand of power from that particular generator is more than generation. So it may be concluded that if negative power indication is for real power then Gen speed is lower than other Gens and if reactive power is negative then excitation of that Gen is overexcitation .
Anybody may put more correct approach.

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