Figure 1 (above). Image displays the various isolated ground readings.

Resistance to ground anomalies can be some of the most difficult motor and motor circuit problems to assess. Given that all motor failure mechanisms result in an increase in motor operating temperature, ultimately insulation problems are the end result. The increased heat thermally degrades and embrittles the winding insulation treatments. Operating stresses, particularly motor starts can result in cracks in the insulation and degradation of resistance to ground.

The use of thermal imaging in building applications (both residential and commercial) is fairly well known, and it’s one of the topics covered in our Level 1 - Thermographic Applications course. We discuss its use for detecting conduction loss or gain, air leakage, and detection of moisture in building systems. There are several standards associated with these particular applications, and many home energy agencies recommend it’s use.

>La vérification de la fonctionnalité d’une caméra infrarouge, également dénommé la « vérification des canaux lacrymaux », est quelque chose que nous recommandons aux thermographes de faire à chaque fois avant de procéder à une inspection. Il ne s'agit pas d'une calibration de votre imageur (qui ne peut être effectuée qu'avec un corps noir), mais d’une démarche qui peut vous fournir un moyen rapide et facile pour déterminer si votre caméra fonctionne correctement, ou si une vérification plus approfondie est justifiée.

The more you understand the motor, as well as the motor circuit for that matter, the better your analysis of test data will be when conducting condition monitoring testing. Assisting in this effort is the National Electrical Manufacturers Association (NEMA) which has been instrumental in helping standardize motor nameplate information.

During the discussion of heat transfer theory in our Level 1 Thermographic Applications training, convection is discussed in great detail. Convection is an important topic in the development of a thermographer since every surface we view through an infrared camera is subject to convective cooling or heating to some degree. Even in conditions where no air movement is detectable to the thermographer, there are in fact differences in temperature, density, moisture, and pressure in the air mass that result in air movement.

Infrared thermography has been used to inspect electrical systems since the 1960s. Even with all the limitations of the technology (i.e. issues with low emissivity, large thermal gradients, and resolution just to name a few), it is still one of the primary testing tools for electrical applications and is now routinely used to successfully inspect electrical systems. Still, environmental variables and equipment limitations can make inspections challenging, especially when it comes to outdoor components. We will examine a few of those issues in this tip.