This video shows one step in collecting motor winding data: how to measure magnet wire.

There are a lot of factors to take into consider when interpreting the bar-bar test or surge test. This articles reviews those factors.

Hay muchos factores a tener en cuenta al interpretar la prueba de barra-barra o la prueba de sobretensión. Este artículo revisa esos factores.

EASA's DC Machine Data Sheet provides all the fields necessary on a simple one-page form to accurately record all the details about the machine being repaired.

A special discounted collection of 6 webinar recordings focusing on DC motor electrical procedures.

Just $30 for EASA members!

The ISO balancing specification for rigid rotors (ISO 1940-1) was innovative when it was introduced decades ago. It established Balance Quality Grades based on the theoretical velocity the mass center of gravity of a rotor would encounter in free space, spinning at the rotor’s normal operating speed. That’s a mouthful of technical jargon, but a practical understanding of the nature of unbalance forces is important in applying balance tolerances to various machine rotors. It is also helpful in understanding the impact of fundamental changes in the recent replacement standard, 21940-11: 2016.

La especificación ISO para balancear rotores rígidos (ISO 1940-1) fue innovadora cuando fue introducida hace varias décadas. Esta norma estableció los Grados de Calidad de Balanceo basada en la velocidad teórica que el centro de masa de un rotor se encontraría en espacio libre, girando a la velocidad de funcionamiento normal del rotor. Esta es terminología técnica difícil de expresar, pero un entendimiento práctico de la naturaleza de las fuerzas de desbalanceo es importante para aplicar las tolerancias de balanceo en rotores de diversas máquinas. Esto también ayuda a entender el impacto de los cambios fundamentales en la reciente norma de reemplazo: 21940-11: 2016.

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.

A convenient incoming inspection report for basic DC motor conditions and test values.

While there are many similarities between 3-phase AC stators and DC armatures, there are some unique aspects to DC armature design; these can be extremely helpful to those who understand some little-known tips. The goal of this article is to share those tips.

There are times when a DC motor or generator experiences a catastrophic failure and the customer wants to know why it happened. One type of failure that seems to stimulate lively conversation is when the failure involves dramatic damage to the brushholders and commutator. The term "flashover" describes the appearance of the failure; the very name conveys an accurate mental image of the failure. The questions that arise next are predictable: "What caused this?" and "What can be done to prevent a recurrence?" Or, if the motor was recently repaired: "What did you do to my motor to cause this?!" The purpose of this article is to help you answer those questions.

We all know that stator cores should be burned at a controlled temperature to prevent lamination deterioration that can lead to harmful eddycurrent losses. But what about armatures?

In the April 2007 issue of CURRENTS, we covered surge testing anomalies, specifically for AC windings. The surge test can be used for DC windings as well. It can be a useful tool for evaluating armatures and some DC fields. A note of caution: If a winding does not have a minimum insulation resistance per ANSI/EASA AR100-2006, it is not safe to apply an overpotential test (surge or high potential). Surge testing shunt fields may not provide meaningful results if the surge pulse decays too quickly - if it dissipates through only the first few hundred turns. To obtain a test voltage high enough to test every turn would require too high a voltage. That high voltage would overstress the groundwall insulation.

This article describes machine balancing of the rotating components of motors and generators, primarily rotors and armatures. The methods described here, in general, can be applied to on-site balancing if the rotating component is accessible. The intent is to describe the methods of attaching balance weights, not determining acceptable balance level or the location and amount of correction weight.

When an armature is rewound, there is always a slim chance that it may be connected incorrectly. If two coil leads are switched, or if the error results in an armature where each coil closes on itself, normal tests will detect the problem. The trouble arises when the misconnection results in a uniform winding. When that happens, the result may be—in effect—an accidental redesign for a different voltage.

The paper "Armature Repair Tips" by Chuck Yung, presented at the EASA Convention, provides detailed guidance on the critical aspects of repairing DC equipment, particularly focusing on the commutator. Yung emphasizes the importance of maintaining proper clamping pressure, understanding the minimum commutator diameter, and ensuring the hardness of the commutator bars. These factors are crucial for the reliable operation of DC machines but are often overlooked.

Describes the correct procedure for taking data from hand-wound DC armatures. Shows how to record the data on typical DC data sheets, and explains the terminology used describing DC data. Points out differences between lap and wave windings.

Provides step-by-step instructions on winding a DC armature, including how to install end fibres and slot liners, how to wind and shape the armature coils and how to make the commutator connections.