Computations. cont'd - ETL-1110-9-10FR0076

ETL 1110-9-10(FR)
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ETL 1110-9-10(FR)

5 Jan 91

is negligible. The tank-to-water resistance is

also negligible because the coating is very

deteriorated.

Calculate RT:

= 1.32 + 0.06 + 0.00

= 1.38 ohms

This is well below the design requirement.

Calculate rectifier voltage (VREC) from equation 1-17:

VREC = (I) (RT) (120%)

Where:

= 25 amp (Current requirement from

step 11, paragraph 2-6a)

= 1.38

ohms

(Total

circuit

from

calculation)

120%

= Rectifier voltage capacity design

safety factor

VREC

= 25 amp x 1.38 ohms x 1.2

VREC

= 41.4 V

Select rectifier.

Based on the design requirements of 41.4 V and 25 amp, a

commercially available 48-V, 28-amp unit is selected. To

prevent over- or under-protection as the water level

varies, automatic potential control is specified.

The

tank-to-water potential is maintained by the controller

through two permanent copper-copper sulfate reference

electrodes suspended beneath the anode wire circle. The

reference electrodes should have a life of at least 5

years.

The tank-to-water potential measured by the

controller should be free of IR drop error.