I realize that the subject of power factor has been discussed ad nauseam on this site, I did my homework and waded through nearly all the discussions / threads on this site. I was able to find just about all that I wanted, however not exactly what I needed.

I will describe my situation as thoroughly as possible, I am familiar with power factor, and methods of correction, and the benefits of PF correction. I am attempting to optimize power factor correction aboard this ship to reduce fuel consumption, and reduce temperatures in the generator rooms.

My biggest problem is being able to convince the Bean counters that the investment is worthwhile, as their eyes roll up, or glaze over when I talk about the simplest of solutions that will improve PF greatly, though not correct completely. I need to take one step at a time to convince non technical management that I am not selling them a perpetual motion machine.

I need to have hard evidence or testimony by a recognized authority that power factor of any magnitude wastes fuel, and I need to be able to quantify the amount of fuel as a function of power factor.

I need to establish that the prime mover (Diesel Engine) must produce the power that ends up wasted as reactive power, and that minimizing the reactive power will conserve fuel.

I need to clarify definitely that the engine must produce the energy to produce the "Apparent Power",(KVA) as this is the vector sum of the true power (KW),and the reactive power (KVAR). And therefore the wasted energy is the difference between the "True Power" (KW), and the "Apparent Power", and thus the wasted energy can be calculated and translated into fuel consumption.

A sample calculation from actual collected Data:

130 turns, 4 DG's, 4 filter stages, 610 KW, 180 KVA, 800 Amperes (Per phase) each DG

Totals 2440 KW, 720 KVA, 5542 Amp (800x 1.732x4) .91 PF

Delta: KVA- KW= 220x 3200 (BTU/hr/KW)/.3 (Assuming 35% engine thermal efficiency, and 5 % transmission loss)= 2.346 MBTU wasted energy. Assuming 140KBTU per gallon of fuel= 16 gallons of fuel consumed, dissipated as heat due to reactive power.

120 turns, 3 DG's, two filter stages 750 KW, 300 KVARS, 1000 Ampere (Per phase) each DG

Totals 2250 KW 900 KVARS 3960 Amp 2494 KVA

.90 PF

Delta KVA: 244x3200/.3=2.6 MBTU/ 140=18.5 gallons per hour.

Are these assumptions reasonable and the calculations correct? answers/ corrections please.

Additionally the temperature of the alternator windings often exceeds 200 degrees F,and generator room ambients of 145 deg F have been observed presumably aggravated by the thermal energy dissipated due to reactive power.

The facts:

I am sailing as Chief engineer on an Institutional Oceanographic Research ship.

The ships propulsion system is Diesel Electric, consisting of four 950 KW Diesel Generators supplying hotel load and propulsion. The two propulsion motors are 2150 HP shunt connected DC motors 150 RPM max each. DC power is provided by 12 pulse SCR drives for Armature current, shunt power is provided by a triac phase shifted power supply that allows reversing the motors electronically without relays by triggering the triacs in either polarity as needed.

Actual observations underway:

When underway at 120 turns with three alternators paralleled the first stage of each filter is enabled, typically reactive power is 200-300 KVARS per Alternator, 600-900 KVARS total lagging. An additional stage or the two 2^nd stages of filtering would be beneficial for additional power factor correction.

With all four Alternators paralleled for maximum speed trials, both second stages of filtering are enabled. This was observed during the recent INSURVE inspection, the reactive power was not noted during this operation I have recovered from the EDI trending history, a summary follows:

Case 1: 120 turns , 3 alternators paralleled, 2 first stage filters enabled.

DG #1 686 KW, 963 amperes 800 KVA .85 PF 50 GPH

DG#2 Secured

DG#3 771 KW 1031 Amperes 857 KVA .89PF 50 GPH

DG#4 703 KW 1015 Amperes 843 KVA .82 PF 49 GPH

2360 KW 149 GPH

Case 2 120 turns, 4 alternators paralleled, 2 first stages, and 2 second stages filters enabled.

DG#1 553 KW 720 Amperes 598 KVA .92 PF 41 GPH

DG#2 721 KW 813 Amperes 676 KVA .93 PF 44 GPH

DG#3 533 KW 714 Amperes 593 KVA .89 PF 36 GPH

DG#4 561 KW 701 Amperes 588 KVA .96 PF 37 GPH

2368 KW 159 GPH

Case 3 70 Turns 2DG's Paralleled, 1 first stage filters enabled

DG 1,and 4 300 KW, ea. 200 KVARS leading 360 KVA .83 PF

Case 4 90 Turns, 3 DG's Paralleled, 2 first stage filters enabled.

DG's 1, 3, 4. 200 KW ea. 20 KVARS Lagging ea. 201 KVA PF .95

Alternators were well balanced, KW, KVARS and current within 5%.

Case 5 120 Turns, 3 DG's Paralleled, 2 first stages filters enabled.

DG 1, 700 KW 950 Amperes 250 KVARS lag 790 KVA .88 PF

DG 3 700 KW 950 Amperes 280 KVARS " 790 KVA .88 PF

DG 4 650 KW 950 Amperes 280 KVARS " 790 KVA .88 PF

Case 6,

130 RPM 4 DG's, 4 Filters

610 KW 180 KVAR 800 Ampere each Alternator , well balanced.

In case 1, and case 2 the true power is nearly identical, in case 2 the Power factor is greatly improved due to the additional capacitors in the additional filter stage.

The fuel consumption in case 2 is 7% greater than in case 1.

All measurements were taken from the EDI Trending menu, the accuracy of which is questionable, as inaccuracies are inherent, such as the EDI display reading DG #2 fuel, and consumption at 8GPH when secured. While warming up engines with no load EDI trending has shown differences fuel flow at 3 and 5 GPH between generator engines. Also the measurements are instantaneous sums taken at different times, and no consideration is taken for sea state at the instants the observations were made.

The additional fuel consumption in case 2 could be due to inaccuracy in the EDI reporting, or due to the parasitic loads of another engine operating.

Of course underway with 1000 ampere loads on the Alternators mostly from propulsion loads harmonic distortion is a serious matter.

The ship is equipped with two static harmonic filters consisting of a large first stage filter with total capacitors rated at a total of 2700 KVA, and smaller second stage with capacitors rated at 1350 KVA each. The filters consist of large Inductors and capacitors, connected in series tuned circuits resonant at 5th, 7th, and 11th harmonics for suppression. The filters are not able to function for reasons I will explain later. However the inductors offer minor impedance at the fundamental 60 Hz, and the large capacitors are useful for adsorbing lagging reactive currents.

Staging of the harmonic filters is accomplished by the ships problem plagued automation system which is programmed to switch filter stages in and out according to the number of Alternators paralleled, with no regard to the network power condition. I have observed as much as 250 kVARs leading on the Alternators, the manufacturer states the alternators are capable of adsorbing 300 KVARS leading before becoming self exciting.

This situation has resulted in numerous "Mystery" blackouts. I have recovered data from the automation system data history that shows one Alternator went out of control immediately prior to the most recent blackout, and I speculate that that Alternator became self excited due to high magnitude of leading current precipitating the blackout.

I have found in the ships sea trials (In 2002) report a recommendation for the harmonic filter stages to be selectively enabled by the engineers to correct reactive power as necessary. This recommendation has not been adopted, and a request to allow me to make this no cost modification has been denied citing "System instability", I argue that the "System Instability" is a result of our inability to selectively enable filter stages, though such an analysis has fallen on deaf ears.

Regarding the harmonic filters, the ships electrical system is ungrounded Delta, required by IEEE45, the filters are off the shelf industrial filters designed and intended for terrestrial use where the Neutral of the network is connected to ground, and connected in Wye with the neutral connected to "Ground" through a resistor to the ships hull. Since the alternators and the ships network is not connected to the ships hull, no "Ground" path exists to complete the circuit for suppressing harmonics.

I have proposed a simple fix of simply reconnecting the filters delta, however a modification such as this must be approved by a licensed EE, and go through the Coast Guard approval process.

How the system ever got Coast Guard approval is a mystery to me!

I have gotten a response through this forum from a company that supplies filters with the ability to switch capacitors electronically, I like the Idea, and have requested consideration by the port Engineer, still waiting for a response!

I have written a 32 page analysis with references on this matter, far too much more to discuss in this submission.

Regards CEKM