MIL-HDBK-1004/10

where

W

=

weight of anodes required

Y

=

15 years

S

=

1 lbs/A yr (in this case includes efficiency factor)

I

=

8.3 A

W

=

15 x 1 x 8.3 = 124.5 pounds

Each anode weighs 44 pounds, thus for the desired system life, the required

number of anodes is:

124.5/44 = 2.8 (say 3)

h)

Number of anodes required for current output (shore side):

N = I/i

where

N

=

number of anodes required

I

=

current requirement (A)

i

=

output per anode (A

N

=

8.3/1.5

N

=

5.5 (say 6)

Thus, the number of anodes will be limited by the output per anode.

i)

Resistance of dc circuit:

Resistance of six anodes is:

1/R = 1/1.86 + 1/1.86 + 1/1.86 + 1/1.86 + 1/1.86 + 1/1.86

R = 0.310 ohms

Resistance of feeder conductor 1,000 feet of HMWPE Size #4 (0.254 ohms per M

feet) (refer to Table 10):

R = 0.254

Total resistance = 0.254 + 0.310 = 0.564 ohms.

j)

Sizing rectifier (shore side):

Requirements:

dc current - 8.3 A

Anode circuit resistance - 0.564 ohms

dc voltage = IR = 8.3 x 0.564 = 4.68 V

A standard rectifier in this range has an output of 12 A at 6 V.

Typical

installation of this system is shown in Figure 114.

206

Integrated Publishing, Inc. |