Traditional rotor bar defect detection systems are often insufficient in sensitivity, record-ability and numerical analysis of test results. Many means of rotor defect detection require the motor to be fully assembled with a functional stator. These limitations have laid the groundwork for the development of a new rotor defect detection technique.

When considering building a large growler for testing armatures and rotors, the initial decision typically is to select a kVA rating. A primary reason for this is that the growler will need to be connected to a power supply of sufficient ampacity at the supply voltage. To help simplify a complex design process, four kVA ratings have been selected for this article.

Cuando se considera la construcción de un gran growler para probar rotores y armaduras, la decisión inicial típica es seleccionar la potencia en kVA. La razón principal para esto es que el growler necesitará ser conectado a una fuente de alimentación que tenga suficiente amperaje. Para ayudar a simplificar el complejo proceso de diseño, en este artículo hemos seleccionado cinco potencias expresadas en kVA.

Vibration readings provide the best early warning of developing problems in a motor or system component. Other parameters to monitor may include operating temperature of critical components, mechanical tolerances, and overall system performance, including outputs such as flow rate, tonnage, and volume.

In a previous article in Plant Engineering ("A systematic approach to AC motor repair," Plant Engineering, April 2015), EASA highlighted the good practices for electrical repair found in ANSI/EASA Standard AR100 Recommended Practice for the Repair of Rotating Electrical Apparatus, and the significant impact they can have on motor efficiency and reliability. But that was only part of the story, because mechanical repairs—and even documentation, cleaning, and inspection—can also markedly affect motor reliability and efficiency.

The intent of this article is to provide an overview of the more common techniques used for dissolved gas analysis (DGA) of mineral oil. Types of gases created during transformer faults. There are several key gases produced during transformer faults. The type of gas and the quantity depends on the materials involved in the fault, the energy dissipated at the fault location and the solubility of the gases in oil.

Topics covered include:

• Types of gases created during transformer faults
• Methods of analysis and interpretation
• Dornenburg ratios
• Rogers ratios
• Key gas method
• Gas limits
• Duval triangle
• Analyzing other gases
• Factors affecting gas concentrations and diagnosis