ETSO-C71

AIRBORNE STATIC ('DC TO DC') ELECTRICAL POWER CONVERTER (FOR AIR CARRIER AIRCRAFT)

1 Applicability

This ETSO gives the requirements which airborne static ('DC to DC') electrical power converters that are manufactured on or after the date of this ETSO must meet in order to be identified with the applicable ETSO marking.

2 Procedures

- 2.1 General

Applicable procedures are detailed in CS-ETSO Subpart A.

- 2.2 Specific

None.

3 Technical Conditions

- 3.1 Basic

- 3.1.1 Minimum Performance Standard

Standards set forth in the attached FAA Standard for 'Airborne Static ('DC to DC') Electrical Power Converter', dated April 15, 1961.

- 3.1.2 Environmental Standard

See CS-ETSO Subpart A paragraph 2.1.

- 3.1.3 Computer Software

None

- 3.2 Specific

None

4 Marking

- 4.1 General

Marking is detailed in CS-ETSO Subpart A paragraph 1.2.

- 4.2 Specific

None.

5 Availability of Referenced Document

See CS-ETSO Subpart A paragraph 3.

FAA STANDARD ASSOCIATED WITH ETSO-C71 FOR AIRBORNE STATIC ('DC TO DC') ELECTRICAL POWER CONVERTER

ED Decision 2003/10/RM

INTRODUCTION

This paper sets forth the minimum performance standards for airborne static ('DC to DC') electrical power converter equipment then used as a part of a navigation or communication system.

Compliance with these standards is required as a means of assuring that the equipment will satisfactorily perform its intended function under all conditions normally encounted in routine aeronautical operations.

Inasmuch as the measured values of a radio equipment performance characteristics may be a function of the method of measurement, standard test conditions and methods of test are also recommended in this paper.

MINIMUM PERFORMANCE STANDARDS FOR AIRBORNE STATIC ('DC TO DC') ELECTRICAL POWER CONVERTER

1.0 GENERAL STANDARDS

1.1 Ratings of Components

The equipment shall not incorporate its design any component of such rating that, when the equipment is operated throughout the range of the specified environmental test, the ratings established by the manufacturer of the component is exceeded.

1.2 Effects of Test

The design of the equipment shall be such that the application of the specified test produces no discernable condition which would be detrimental to the reliability of equipment manufactured in accordance with such design.

2.0 MINIMUM PERFORMANCE STANDARDS UNDER STANDARD TEST CONDITIONS

The test procedures applicable to a determination of the performances of the airborne static ('DC to DC') electrical power converter equipment are set forth in Appendix 'A' of this paper.

2.1 Nominal Output Voltage and Current

The nominal output voltage and current shall not be less than that specified by the manufactuer's ratings. Further, the equipment shall be capable of delivering at least 10% more output power than the manufacturers specified rating for a period of two (2) hours.

2.2 Regulation

Regulation under standard conditions shall not exceed 12%. For the purpose of this standard, regulation is defined as:

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2.3 Ripple

Ripple in the output DC voltage at maximum rated output load shall not exceed 1/10% of the output voltage when shunted by a 2 mfd capacitor and the ripple on the DC input leads is equal to 2 volts peak to peak at a frequency of 400 cps. For equipment designed for operation on 13.75 volts DC, the ripple on the input leads need not exceed 1 volt peak to peak.

2.4 Over Voltage

There shall be no permanent damage to any of the solid state devices (transistors) or the components when the power converter is delivering full rated output power and is subjected to the following over voltage conditions:

- (a) The input DC voltage is increased to 50% above the standard operating voltage for a duration of not less than five minutes.

2.5 Short Circuit Conditions

There shall be no degradation of the power converter or its components as a result of a sustained short circuit applied separately to each output of a multiple output power converter, or simultaneously to all DC outputs for a period of not less than one minute. Within five minutes after removal of the short circuit condition, the equipment shall be capable of continuous operation at the manuf acturer's rated output load for a period of eight hours without, degradation of performance.

2.6 Emission of Radio Frequency Energy

The emission of radio frequency energy at discreet frequencies within the range of 90 kc to 1500 Mc shall not exceed 200 microvolts between any cable terminal to ground.

Note: It is recognized that the radio frequency emissions having a level considerably less than the maximum permitted by the above standard are capable off interfering with the operation of other electronic equipment in an aircraft installation. It is also recognized that the method of reducing the level of emission of radio frequency energy to much lower values are known. However, at the present state of the art, large and expensive filters are often required in addition to the exercise of care in the mechanical and electrical design of equipment. The end result is often a compromise between what is desired and cost.

In view of the above, the emission standards were set at a level which can be met by the exercise of reasonable care in design and yet effect the reduction in the present overall interference problem. Lower emission levels are desirable and it is, therefore, recommended that the equipment manufacturers make a determined effort to reduce the level of emission from electronic equipment, to the lowest practicable value below that specified above.

2.7 Dielectric Strength

The equipment shall withstand without evidence of damage the application of a sinusoidal voltage between each transformer output winding and frame for a period of five seconds. The RMS value of the sinusoidal voltage applied shall be either five times the maximum operating voltage existing across that winding during operation when delivering full rated output, or 500 volts, whichever is greater. During the application of this test, all diodes, transistors, and capacitors may be disconnected.

3.0 MINIMUM PERFORMANCE STAND ARDS UNDER ENVIRONMENTAL TEST CONDITIONS

The test procedure applicable to a determination of the performance of radio equipment under environmental test conditions are set, forth in RTCA Paper 100-54/D0-60,

'Environmental Test Procedures -Airborne Radio Equipment,' and amendment Paper 256 - 58/ EC-366 dated November 13, 1958. This paper outlines environmental test procedures for equipment designed to operate under three environmental test conditions as specified therein under Procedures A, B, and C. Only airborne static ('DC to DC') electrical power converter equipment which meets the operating requirements outlined under Procedure A or Procedure B of this paper, as amended, is applicable under this standard.

The applicable electrical test procedures are set forth in Appendix 'A' of this standard.

3.1 Low Temperature Test

When the equipment is subjected to the low temperature test and, with primary power voltage 10% less than standard test voltage applied, the following requirements shall be met:

- (a) The output voltage shall not vary more than 121/2% from that obtained at standard test conditions. - (b) The requirements of paragraph 2.3 shall be met.

3.2 Altitude Test

When the equipment is subjected to the altitude test, the requirements of paragraphs 2.1, 2.2, and 2.3 shall be met.

3.3 Humidity Test

After subjection to humidity and within fifteen (15) minutes from the time primary power is applied, the requirements of 2.1, 2.2, and 2.3 shall be met.

3.4 High Temperature Test

When the equipment is subjected to the high temperature test and with primary power voltage 10% higher than standard test voltage applied, the following requirements shall be met:

- (a) The output voltage shall not vary more than 121/2% from that obtained at standard test conditions. - (b) The requirements of paragraphs 2.1, 2.2, and 2.3 shall be met.

3.5 Temperature Variation Test

When the equipment is subjected to the temperature variation tests, the requirements of paragraphs 2.2 and 2.3 shall be met.

3.6 Vibration Test

When the equipment is subjected to the vibration test, the requirements of paragraphs 2.2 and 2.3 shall be met.

3.7 Shock Test

- (a) Following the application of 15 G shocks, the requirements of paragraphs 2.2 and 2.3 shall be met. - (b) Following the application of 30 G shocks, the power converter shall have remained in its mounting by its intended means and no parts of the equipment or its mounting shall have become detached and free from the equipment.*

3.8 Low Voltage Test

- (a) When the primary power voltage(s) is 80% of the standard test, voltage(s), the equipment shall operate electrically. - (b) Gradual reduction of the primary voltage(s) from 80% to 50% of standard test voltage(s) shall produce no condition detrimental to the reliability of the equipment. - (c) Gradual reduction of the primary power voltage(s) from 50% to 0%, of standard test, voltage(s) shall produce no evidence external to the equipment of the presence of fire or smoke.*

* Test tests may be conducted after other tests are completed.

FAA STANDARD ASSOCIATED WITH ETSO-C71 -APPENDIX A - TEST PROCEDURES AIRBORNE STATIC ('DC TO DC') ELECTRICAL POWER CONVERTER

ED Decision 2003/10/RM

- 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.