Insulation Resistance and Isolation Capabilities
Other Technical Articles
In the article on swift coil economizers we discussed the importance of high insulation resistance, "IR", for many high voltage relay applications.
Controlling environmental conditions for testing relays or, for that matter, making any insulation resistance measurement is critical for accuracy and consistency. Subtle changes in humidity, dust, or temperature can cause major changes in IR measurements.
Typically, customers will require a leakage current at a specified voltage in addition to an insulation resistance requirement. Insulation resistance will generally be specified at a lower voltage, 500 or 1000 volts, where influences on the external paths are not apt to cause problems. The external paths on sealed vacuum or gas filled relays are the areas on the surface of the relay exposed to the atmosphere, between high voltage terminals or from the high voltage terminals to the base of the relay. Leakage current is specified at a higher voltage, the operating or test voltage of the relay.
Together these specifications provide a clear picture of how well a relay will provide isolation. However, it is important to provide a controlled environment when making measurements to assure consistency.