Surge test replaces Megohmmeter?
One of the most frequent questions we receive from our customers when they are deciding to purchase Surge Test equipment is: What is this equipment for? We will answer this and other questions in this post.
The electrical surge test consists of generating a momentary stress on the coil, applying a certain voltage level to it (Normally 2 x Line voltage + 1000V) with a certain energy, using a quick-release switch. The electrical circuit of the equipment + coil (motor, generator, alternator…) forms an RLC circuit: Resistor, Inductor and Capacitor, this circuit is responsible for generating the signal expected for analysis, which will normally be a damped sinusoid. This sinusoid is read and stored in the equipment’s memory and later compared with the sinusoid of the other phases or the standard sinusoid.
This background is necessary to understand how the equipment operates. With this information in mind we can answer the initial question: The Surge Test equipment serves mainly to identify insulation failures between turns of the same coil, that is, when two wires or more are close to each other, the only thing that allows correct operation is the insulation between them, if there is a weakening or failure of this insulation, small discharges will occur from one wire to the other during the use of the machine, these discharges are known as SHORT CIRCUIT BETWEEN TURN.
The short circuit between turns is the initial phase of the problem, the machine (Motor, Generator…) will continue to work normally for a certain period, the fault will continue to occur intermittently, over time the point where the fault is occurring The short circuit will progressively increase due to the carbonization of that point, eventually generating more serious failures such as a short between phases or in the worst case, the machine burning out.
The Surge test is the only one that can identify this failure in the initial stage, being a very useful tool in preventive maintenance, as well as in quality control in coil manufacturing.
The example above exemplifies the three-phase response of a motor with a short circuit in one of the phases, we can see that two of the red responses are overlapping and one is completely out of phase with the others, by comparing the responses it is possible to obtain a result using in this case digital analysis changing area, frequency and damping (Understand more about this LINK).
Surge Test replaces Megohmmeter?
Another frequent question is whether the Surge Test replaces Megohmmeter, Hipot or Milliohmmeter.
Unfortunately, this is also true in the opposite direction, other equipment or tests do not replace the Surge Test.
The principle of the Surge test identifies faults that the Megohmmeter is not capable of identifying, the Megohmeter subjects the coil or phases to the same potential in relation to the machine housing, not generating potential differences between turns, that is, not identifying faults between turns. The Surge Test also does not replace the Megohmmeter, as it does not measure the resistance of the existing dielectric.
This also applies to other equipment and tests, each of which tests a certain characteristic or measures a certain magnitude of the machine under test.
