Sep 11, 2012
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Electrical Testing

       Testing is critical for ensuring the performance of electrical systems or components, whether it’s for military or consumer products. AERO NAV LABORATORIES provides a wide variety of electrical testing services tailored to the specific requirements of each individual project. The following article describes some of the electrical tests which are most often performed by AERO NAV LABS.
DIELECTRIC WITHSTANDING VOLTAGE

The dielectric withstanding voltage test (also called high-potential, over-potential voltage-breakdown, or dielectric-strength test) consists of the application of a voltage significantly higher than rated voltage for a specific time, between mutually insulated portions of a component part or between insulated portions and ground. This is used to prove that the component part can operate safely at its rated voltage and withstand momentary over-potentials due to switching, surges, and other similar phenomena.

ELECTRIC POWER SYSTEM CHARACTERISTICS

This test is also known as the power supply line voltage and frequency variations test. A few of the measured characteristics are: voltage and frequency modulation, voltage spike, and voltage transient recovery.

VOLTAGE AND FREQUENCY MODULATION
The voltage and frequency modulation testing is the measurement of the effect of supply voltage and frequency variation on the equipment operation. It might be caused, for example, by regularly or randomly repeated applied pulsed loading.

VOLTAGE SPIKE
The spike voltage testing is the measurement of the effect of a voltage change of very short duration (less than 1ms) on the equipment operation. A voltage spike occurs when the maximum voltage significantly exceeds its average amplitude. This test determines whether the equipment can withstand the effects of voltage spikes arriving at the equipment on its power leads, either ac or dc.

VOLTAGE TRANSIENT RECOVERY
The voltage transient recovery test is a measurement of the voltage and time from initiation of the external supply line disturbance until the voltage recovers and remains within the allowable voltage tolerance limits.

ELECTRICAL CONTACTS

The electrical contact testing is performed to determine the reliability of equipment under various contacting conditions. A few types of electrical contact tests are: contact-chatter monitoring, contact resistance, intermediate, and low level contact switching.

CONTACT-CHATTER MONITORING
This test is conducted for the purpose of detecting contact-chatter in electrical and electronic components having movable electrical contacts, such as replays, switches, circuit breakers, etc. It is performed where it is required that the contacts do not open or close momentarily, for longer than a specified time-duration, under environmental test conditions, such as vibration, shock, or acceleration.

CONTACT RESISTANCE
The purpose of the contact-resistance test is to determine the resistance offered to a flow of current during its passage between the electrical-contacting surfaces of connecting components, such as plugs, jacks, connectors, and sockets, or between the electrical contacts of current-controlling components, such as switches, relays, and circuit breakers.

INTERMEDIATE LEVEL CURRENT SWITCHING
This test is conducted for the purpose of determining the electrical contact reliability of such items as electromechanical relays, switches, etc., under intermediate current switching conditions. An intermediate current switching circuit is one in which there is insufficient voltage and stored energy to cause contact arcing during opening or closing of mating contacts, but which have sufficient energy to cause melting of the contact material.

LOW LEVEL CONTACT SWITCHING
This test is conducted for the purpose of determining electrical contact reliability under low-level switching conditions in the environment in which the contacts operate. A low level switching circuit is one in which the voltage and stored energy are sufficiently small so that the resistance of a pair of contacts is not affected by electrical phenomena associated with the electrical current flow or the switching.

ELECTRICAL MEASUREMENTS

The tests are performed to measure and collect data from electrical and electronic parts using various measurement methods including, but not limited, to the following: capacitance, resistance, winding resistance, insulation resistance, magnetic permeability, power input, and quality factor Q.

CAPACITANCE
The capacitance test is used to measure the capacitance of component parts. Preferred test frequencies for this measurement are 60 Hz, 120 Hz, 1 kHz, 100 kHz, and 1 MHz.

DC RESISTANCE
The dc resistance test is used to measure the direct-current (dc) resistance of resistors, electromagnetic windings of components, conductors, etc.

ELECTRICAL WINDING RESISTANCE
Electrical winding resistance measurements are performed on electrical machinery. These measurements are commonly used to determine temperature rises, to compare winding resistance with design data, to compare production models against the first article model, and to detect defective windings.

INSULATION RESISTANCE
The insulation resistance test measures the resistance offered by the insulating members of a component part to an impressed direct voltage tending to produce a leakage or current through or on the surface of these members. The test is especially helpful in determining the extent to which insulating properties are affected by deteriorative influences, such as heat, moisture, dirt, oxidation, or loss of volatile materials.

MAGNETIC PERMEABILITY
This test measures the magnetic permeability of enclosed materials and equipment. It demonstrates whether the test item meets the magnetic signature limitations.

POWER INPUT
The purpose of this test is to measure the electrical power including parameters such as power factor, voltage, current, frequency, waveform phase, etc., applied to the input terminals of equipment under various conditions of operation.

CURRENT WAVEFORM TEST
This test measures the harmonic content between input line frequency and 20 kHz of current waveforms.

QUALITY FACTOR (Q)
The purpose of this test is to measure the quality factor, commonly called Q, of electronic parts such as capacitors and inductors. By definition, the factor Q expresses the ratio of reactance to effective resistance of a circuit element.

RESISTANCE-TEMPERATURE CHARACTERISTIC
The resistance-temperature characteristic test measures the percentage change in direct-current (dc) ohmic resistance from the dc ohmic resistance at the reference temperature.

EMERGENCY CONDITIONS

The emergency conditions test determines if equipment is operating properly under atypical situations or occurrences, of a nature that may result in electrical power system deviations. The test is used to determine, for example, the following:
* Power system sudden interruptions
* Rapid re-application of power after an interruption
* Power source voltage and frequency decay test, such as may occur with an       inadvertent shutdown.
* Emergency condition voltage and frequency tolerances.

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