What is Infrared Scanning? How is it done?
Infrared scanning is a method that is utilized to locate high-resistance connections ("hot spots") by using a camera that turns infrared radiation into a visible image.
This test is performed with the equipment in service carrying normal load current, which is a major advantage because it does not interrupt normal production. Exposure to energized equipment, of course, carries the possibility of exposure to electrical hazards.
The operator shall recognize and deal with such potential hazards accordingly.
The most common use of infrared scanning is to locate loose or corroded connections in switchboards, panel boards, bus ways, and motor starters.
It is a comparative type test in which the person who performs the scan is looking for an area that appears brighter (hotter) than a similar area, such as a lug connection on phase "A" as it compares to similar connections on phases "B" and "C"
The person should be aware of how unbalanced loading may affect heating, thereby giving an indication similar to looseness.
One limitation of infrared scanning is that the equipment has to be carrying enough load for the hot spots to be visible.
At lower loads, there may not be enough heat generated to locate a problem, even when the connections are significantly looser than they should be.
MOTOR SURGE COMPARISON TESTING BASIC INFORMATION AND TUTORIALS
What is Motor surge comparison testing? How is it done?
Motor surge comparison testing addresses the problem of insufficient test voltage to find the weak insulation between turns by utilizing a high-voltage pulse. Two identical high-voltage pulses are introduced into two windings of a motor.
The propagation of the pulse through one winding is compared to the propagation of the identical pulse through the winding next to it.
An oscilloscope (usually built into the surge tester) is used to look at the traces and to compare them. The patterns should be identical (or very nearly so) and can appear as one trace (two superimposed traces) if both windings are good.
A turn-to-turn failure (or a failure to ground) is indicated by two distinctly different traces appearing on the oscilloscope.
Motor surge comparison testing has been used by motor winding shops for many years. There are now portable models that are available for field testing.
Motor surge comparison testing has proven to be a valuable tool in detecting the early stages of a winding failure, both from the standpoint of preventing an unexpected failure during operation and preventing a catastrophic failure of the motor so it can be repaired instead of needing to be replaced.
Motor surge comparison testing addresses the problem of insufficient test voltage to find the weak insulation between turns by utilizing a high-voltage pulse. Two identical high-voltage pulses are introduced into two windings of a motor.
The propagation of the pulse through one winding is compared to the propagation of the identical pulse through the winding next to it.
An oscilloscope (usually built into the surge tester) is used to look at the traces and to compare them. The patterns should be identical (or very nearly so) and can appear as one trace (two superimposed traces) if both windings are good.
A turn-to-turn failure (or a failure to ground) is indicated by two distinctly different traces appearing on the oscilloscope.
Motor surge comparison testing has been used by motor winding shops for many years. There are now portable models that are available for field testing.
Motor surge comparison testing has proven to be a valuable tool in detecting the early stages of a winding failure, both from the standpoint of preventing an unexpected failure during operation and preventing a catastrophic failure of the motor so it can be repaired instead of needing to be replaced.
TRANSFORMER TURNS RATIO TESTING BASIC INFORMATION AND TUTORIALS
What is Transformer turns ratio (TTR) testing? How is it done?
The voltage across the primary of a transformer is directly proportional to the voltage across the secondary, multiplied by the ratio of primary winding turns to secondary winding turns.
In order to ensure that the transformer was wound properly when it was new, and to help locate subsequent turn-to-turn faults in the winding, it is common practice to perform a TTR test.
The simplest method would be to energize one primary winding with a known voltage (that is less than or equal to the windingÕs rating) and measure the voltage on the other winding.
Since source test voltages can fluctuate, it is often more accurate to use a test set, designed for this purpose, that creates the test voltage internally, thus giving a direct read-out of the ratio measured.
The voltage across the primary of a transformer is directly proportional to the voltage across the secondary, multiplied by the ratio of primary winding turns to secondary winding turns.
In order to ensure that the transformer was wound properly when it was new, and to help locate subsequent turn-to-turn faults in the winding, it is common practice to perform a TTR test.
The simplest method would be to energize one primary winding with a known voltage (that is less than or equal to the windingÕs rating) and measure the voltage on the other winding.
Since source test voltages can fluctuate, it is often more accurate to use a test set, designed for this purpose, that creates the test voltage internally, thus giving a direct read-out of the ratio measured.
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