FAA Standard associated with ETSO-C71 – Appendix A - Test Procedures Airborne Static („DC to DC“) Electrical Power Converter

A. Power Input Voltage Unless otherwise specified, all tests shall be conducted with the power input voltage adjusted to the design voltage within ±2%. The input voltage shall be measured at the power converter input terminals.

Note: Design voltages in use as of the date of this report are 13.75 VDC and 27.5 VDC and defined as standard condition.

B. Adjustment of Equipment. The equipment under test shall be properly adjusted in accordance with the manufacturer’s recommended practices prior to the application of the specified tests.

C. Test Equipment Precautions. Due precautions shall be taken during the conduct of these tests to prevent the introduction of error resulting from the improper connection of voltmeters, oscilloscopes and other test instruments across the input and output impedances of the equipment under test.

D. Ambient Conditions. Unless otherwise specified, all its shall be conducted under conditions of ambient room temperature, pressure and humidity. However, the room temperature shall not be lower than 10° C.

E. Warm-up Period. Unless otherwise specified, all tests shall be conducted after a warm-up period of not less than fifteen (15) minutes.

F. Connected Loads. Unless otherwise specified, all tests shall be performed with the equipment connected to loads having the impedance value for which it is desired.

TEST PROCEDURES

The test procedures set forth below are satisfactory for use in determining the performance of airborne static („DC to DC“) electrical power converter equipment. Test procedure’s which provide equivalent information may also be used.

T-1 Power Output

EQUIPMENT REQUIRED

Voltmeter – Weston Model 931 or equivalent.

Ammeter – Weston Model 931 or equivalent.

MEASUREMENT PROCEDURE

Connect the power converter to the appropriate input power source with the ammeter in series with the output and the voltmeter connected across the output. The manufacturer’s specified load shall be connected across the output(s). The output load impedance should be adjusted to the manufacturer’s specified rating.

Determine that the nominal output voltage and current is at least that specified by the manufacturer and that the equipment is capable of delivering at least 10% more output power than the manufacturer’s specified rating for a period of two (2) hours.

T-2 Regulation

EQUIPMENT REQUIRED

Voltmeter – Weston Model 931 or equivalent.

Ammeter – Weston Model 931 or equivalent.

MEASUREMENT PROCEDURE

Connect the power converter to the appropriate input power source with the ammeter in series with the output and the voltmeter connected across the output. The manufacturer’s rated load should be connected across the output(s).

Vary the load impedance from maximum rated load to 20% of maximum rated load and note the output voltage(s) at these two load settings. Calculate the percent regulation using the formula specified in paragraph 2.2.

T-3 Ripple

EQUIPMENT REQUIRED

Hewlett Packard Oscilloscope Model 150A or equivalent.

MEASUREMENT PROCEDURE

Connect the power converter to the appropriate input power source with the power converter delivering maximum rated load. Also connect a two (2) microfarad capacitor of the proper DC working voltage across the output under test.

Using the oscilloscope as a peak to peak voltage indicating device, measure the ripple on the output power source and all output voltage(s) when ripple on the DC input leads is equal to 2 volts peak to peak at a frequency of 400 cps or 1 volt peak to peak, whichever is applicable.

T-4 Overvoltage

EQUIPMENT REQUIRED

Perkins Power Supply Model MR 1040- 30A or equivalent.

MEASUREMENT PROCEDURE

(a) Connect the equipment to the Perkins Model MR 1040-30A power supply with the equipment delivering full rated output power. Increase the output voltage from the Model MR 1040-30A power supply to 50% greater than the input voltage for which the equipment is designed for a duration of five (5) minutes.

(b) Following this, determine that the output voltage and current is the same as that prior to the application of the overvoltage.

T5 Short Circuit Conditions

EQUIPMENT REQUIRED

Voltmeter – Weston Model 931 or equivalent.

Ammeter – Weston Model 931 or equivalent.

MEASUREMENT PROCEDURE

With the power converter connected to the appropriate input power source and the equipment delivering full rated output power, apply a sustained short circuit separately to each output of multiple output power converters or simultaneously to all DC outputs for a period of not less than one (1) minute.

Following this, determine that the equipment is capable of delivering the manufacturer’s rated output power for a period of at least eight (8) hours.

This test shall be conducted after the overvoltage test specified in T-4, Overvoltage, is completed.

T-6 Emission of Radio Frequency Energy

EQUIPMENT REQUIRED

Noise and Field Strength Meters as follows:

Stoddard models NM-20B, NM-5A, AM-10A, and NM-50A or equivalent.

MEASUREMENT PROCEDURE

Connect the power converter to the appropriate input power source with the equipment delivering full rated output power. The input power leads shall be from 10 to 12 feet in length, normally terminated and cabled, and shall not be enclosed in conduit.

With the noise meter, measure the rf voltage developed between ground and each of the primary input and power output leads, tuning the noise meter throughout the range of frequencies from 90 kc to 1500 Mc.

T-7 Dielectric Strength

EQUIPMENT REQUIRED

Variable AC power source.

MEASUREMENT PROCEDURE

(a) Apply an a-c voltage, at the frequency used in normal operation, between each transformer output winding and frame for a period of five (5) seconds. The RMS value of the sinusoidal voltage applied shall be either five (5) times the maximum operating voltage existing across that winding during operation voltage delivering full rated output, or 500 volts, whichever is greater.

(b) Following this, determine that the output voltage and current under full load conditions is the same as that prior to the application of the tests.