UFC 3-535-01
17 November 2005
Figure 15-4. Sample Calculation of CCR Test Data (Cont.)
(2 of 2)
SAMPLE CALCULATIONS, CCR TESTING (Cont.)
NOTE: Traditional method (FAA AC 150/5340-24, Figure 6) for determining the load KW
assumes that the CCR powers a unity power factor lamp circuit. With REILs, new type signs,
and runway guard lights (wig-wags), a unity power factor is not representative, and power factor
must be considered.
MEASURED RESULTS (Case 1):
Output current at Step 5 = 6.52A
Output voltage at Step 5 = 2,880V
Total KVA Load based on measurements = 6.52A x 2.88kV = 18.8KVA
CONCLUSIONS: The output current is within FAA tolerance. The total KVA measured is
slightly higher than the calculated load. This may be due to slightly higher actual fixture losses
than assumed values. Overall, the CCR is operating satisfactorily.
MEASURED RESULTS (Case 2):
Output current at Step 5 = 6.52A
Output voltage at Step 5 = 1,880V
Total KVA Load based on measurements = 6.52A x 1.88kV = 12.3KVA
CONCLUSIONS: The output current is within FAA tolerance. The total KVA measured is
significantly less than the calculated load. The results suggest a partial shorting of the load.
MEASURED RESULTS (Case 3):
Output current at Step 5 = 6.30A
Output voltage at Step 5 = 2,550V
From test results, Total KVA Load = 6.30A x 2.55kV = 16.1KVA
CONCLUSIONS: The output current is below that allowed by FAA tolerance. The total KVA
measured is below the normal value (2,880V) as found in first test. Results indicate faulty CCR,
and a short circuit test should be performed on the CCR.
CCR TAP SETTING:
In above example, it was found that under normal operating conditions (Case 1) the total load
is 18.8KVA, or about 63 percent of the rated 30KW output for the CCR. To achieve minimum
distorted sinusoidal wave form where there is a significant harmonic presence (particularly for
SCR type CCRs), it is desired to have CCR operate at least at 80 percent of its rated output. If
the CCR is provided with tap setting arrangement (for example 25 percent, 50 percent, 75
percent), then tap the CCR on 75 percent (at 22.5KW). This will bring the total connected load,
as measured, to about 84 percent of CCR output KW.
NOTE: Analysis compares KVA with KW. This is because the rated output of the CCR is
specified in KW in compliance with FAA AC 150/5345-10E. However, load measurements result
in KVA. The requirement for total load in KVA to be below the CCR output in KW under
operational conditions ensures that the CCR is not overloaded.
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