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How to Select Power Supplies for Aerospace Test by ITECH...

9/4/2019

 
Various kinds of electrical equipment with different functionality are combined to ensure the normal operation of an airplane, aircraft, satellite, etc., thereby contributing to the need for long-term development of instruments for the aerospace market. The research, development, production and testing of aerospace electronic equipment is be subject to multiple tests, including reliability tests, function tests, protective action tests, electromagnetic interference tests, all of which depend on a high-precision, high-performance programmable DC power supply. In the aerospace field, the programmable DC power supply is mainly used in the testing of DC-DC power supply modules, batteries, flight simulators and other DC electrical equipment.

Reliability Test

The Reliability Test of electrical equipment usually includes the voltage drop test, temperature rise test, ON/OFF test, aging test etc. Electrical equipment tests for the aerospace market should be more stringent than for conventional markets.  Often equipment is required to work steadily in conditions of abnormal power. For example, the power supply system of the airplane, which supplies DC power to electrical equipment, may be subject to over-voltage or under-voltage at times.  The ability to continue to function normally in the case of an abnormality can guarantee the functions and safety of the airplane. Therefore, the over-voltage and under-voltage test is essential. The DC power supply can simulate the power supply system in test. The voltage changes of the airplane power supply system can be simulated by outputting a continuous voltage variation waveform, to the electrical equipment and test whether the equipment can work normally under those conditions. Fig. 1 shows the voltage waveform output by an airplane power supply system simulated by the DC power supply in the over-voltage and under-voltage test of electrical equipment on an airplane. 
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The voltage of most airplane power supply systems is 28V. Therefore, the voltage of the output waveform of the DC power supply is 28V, kept for 5min. The 50V over-voltage surge is kept for 50ms, the normal power supply voltage for 10s and the 0V under-voltage surge for 7s. The cycle test should be done three times.

The waveform should be outputted by programming the DC power supply. ITECH's programmable DC power supply series have a List function, which enables engineers to set the voltage and time through the panel keys, thus simplifying waveform editing. In addition, the DC power supply used in the test must have high speed characters and the ability to alter the voltage rise in a short period of time; otherwise, the working status of the airplane power supply system cannot be truly simulated. For example, the voltage rise time from 28V to 50V is only 50ms (shown in Fig. 1), and then the voltage drops to 28V. The voltage rise time of an ordinary DC power supply is approximately 150ms. Fig. 2 shows the voltage waveform output by the low-speed power supply.
Picture
According to the comparison of Fig. 2 and Fig. 1, it can be found that the voltage of the ordinary power supply rises or drops slowly and cannot meet the waveform requirements of the test. The voltage rise time of ITECH's programmable DC power supply is less than 10ms; and can therefore, be applied in precision tests of the aerospace field. 

Aging Test 

The aging test is necessary for electronic equipment, particularly for electric equipment in the aerospace field. As the aircraft or spacecraft generally run a long time in the atmosphere or space, the aging test of electrical equipment is important. In the aging test, the DC power supply is mainly used for continuously supplying power to the tested equipment for a long time. Therefore, the capability of long-time steady operation is necessary for a power supply for the aging test. Fig. 3 is the schematic diagram of aging of a DC-DC power supply module.
Picture
As shown in Fig. 3, as the aging test time is long, an aging cabinet consisting of multiple power supplies and electronic loads. The simultaneous aging of hundreds of DC-DC power supply modules can be realised by means of software monitoring.

These units are easy to fit in a rack and conserve space in a cabinet.  ITECH's DC power supply series are manufactured in a standard size and with high power density. Considering the energy consumption of power supplies, electronic loads and other testing equipment over a long period, ITECH's products are designed with an intelligent fan, which not only achieves excellent cooling performance but also saves power. In terms of compatability between the testing equipment and aging test software, ITECH's DC Power Supplies are provided with a number of built-in interfaces, thereby saving substantially in configuration costs. Built-in interfaces can help to improve the communication speed and stability, with general communication speeds of less than 30ms. The temperature drift coefficiency of ITECH's DC power supply series is small, which ensures stable voltage and current in the long-time aging test.

Electromagnetic Interference Test

Electronic devices used in airplanes, satellites and other aerospace equipment work independently to complete flight tasks. However, almost all electronic devices can produce electromagnetic waves during operation, causing interference to other devices. For example, the cockpit of the airplane is equipped with a number of electronic communication devices - if one such device fails to operate normally as a result of electromagnetic interference, serious consequences could occur. Therefore, the electromagnetic interference test has been a concern of engineers for a long time. Note: the power supply used to test the equipment in the electromagnetic interference test will be affected by electromagnetic interference. In case of poor anti-interference capability, the power supply may fail to normally power the tested object, and the test will fail. The output of the power supply will be subject to serious ripple interference in this environment and it may even fail in terms of normal output. Therefore, the anti-interference capability of the power supply should be taken into account. ITECH's power supply series are provided with complete shielding protection, which effectively prevents interference.
Picture
Function Test

The value of electrical equipment in the aerospace field lies in their functions. The DC power supply should meet more stringent requirements in the function test. Due to the diversity and complexity of electrical equipment in an airplane and the irregular opening or closing of multiple devices, the load regulation rate and response time of the power supply should comply with stringent requirements. In case of low response speed, the power supply may be subject to outage and other faults when tested electrical equipment is opened and closed irregularly, resulting in failure of the test. Therefore, attention should be paid to the load regulation rate and response time of the power supply.

Protective Action Test

Aircraft electronic devices are set in parallel; therefore, engineers should consider the influence on other devices in case of abnormality from a device. In the protective action test, the circuit should be cut off promptly in the case of abnormality of an electronic device, to prevent the power line from burning and the other devices from being affected. Therefore, the normal operation of the power supply should be ensured in case of abnormality. In the test, multiple electronic devices are driven by one DC power supply, and one or more tested device(s) are made abnormal to test the influence on other circuits. The power supply should meet certain requirements. As for the ordinary power supply, all the circuits may be directly cut off in case of abnormality of one device (such as short-circuiting), and the test will fail.

ITECH's power supplies have delay protection.  Generally, a programmable DC power supply is necessary in the reliability, function, protection, electromagnetic interference and aging tests of electronic equipment in the aerospace field. They are mainly used for powering the tested equipment and simulating the operating environment to output different kinds of voltage waveforms. In summary, the programmable DC power supply should be selected according to the following requirements:
  1. Programming function
  2. Short time of voltage rise
  3. High stability
  4. Standard size
  5. Good cooling performance
  6. High communication speed
  7. Good anti-interference capability
  8. Good load regulation rate and response time
  9. Delay protection function

Based on comprehensive considerations, ITECH's range of DC Programmable Power Supplies are the best choice.  Contact Us for further information.

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