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Author Topic:   Loss of Electrical Power
jimh posted 12-27-2011 08:03 PM ET (US)   Profile for jimh   Send Email to jimh  
Many readers may have experienced a dead battery. How about a loss of electrical power on a major ship? Interesting reading:

Report on the investigation of the catastrophic failure of a capacitor
in the aft harmonic filter room on board
RMS Queen Mary 2
while approaching Barcelona 23 September 2010

http://www.maib.gov.uk/cms_resources.cfm?file=/QM2Webreport.pdf

Jerry Townsend posted 12-27-2011 11:05 PM ET (US)     Profile for Jerry Townsend  Send Email to Jerry Townsend     
Interesting indeed Jim - thanks.

There had to be a lot of energy involved to cause that much damage. And then, those capacitors are BIG - and probably big enough to swamp the BWs that many of us have.

I also appreciated their conducting the investigation - not in the interest of blaming someone.

And then, I didn't fully realize how the frequency controlled motors were controlled.

Thanks again ----- Jerry/Idaho

jimh posted 12-28-2011 07:04 AM ET (US)     Profile for jimh  Send Email to jimh     
The Harmonic Filter (HF) described in the report is designed to shunt higher-order harmonic energy in the 60-Hz 11,000-VAC power. The HF components are a series-resonant L/C circuit with values of

C = 108.8-uF
L = 0.507-mH

as shown in Figure 14, Rank 11.3 of harmonic filters

The resonant frequency of that combination is found from

F = 1 / (2 * pi * LC^0.5)

and for those values computes to be 677.6-Hz

The relationship to the primary frequency is

677.6 / 60 = 11.29 --> 11.3 (and hence the name of the filter component)

At series resonance the filter has a low impedance and should tend to shunt any current around that frequency present in the 60-AC. I don't know anything about high-power and high-voltage AC power conditioning, but it seems like a brute force method. Even though the elements are reactive, and assuming they are very high-Q, low power-loss devices, there must be some significant power flowing through them.

If we consider that the harmonic content of the power could be about 7-percent, it should be noted that the power levels are measured in Mega-Watts, so 7-percent of a couple of Mega-Watts is still nothing to sneeze at.

On a non-electrical note, I found it interesting that when the QM2 lost propulsion power and was not able to maneuver, the narrative notes that "the 'not under command' [navigation] lights were switched on." That would be an interesting sight to see--a major ship at sea showing those navigation lights. By the way, the NOT UNDER COMMAND indication is "two all-round red lights in a vertical line where they can best be seen." Cf.:

RULE 27
http://www.navcen.uscg.gov/?pageName=Rule27

The mnemonic used to help remember the navigation lights for NOT UNDER COMMAND is "red over red; the captain is dead." The equivalent day shape is two black balls. There is also a memory aid for that, although a bit vulgar: "the captain's dead; his b*lls are in the rigging."

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