Unlike their AC counterparts, DC machines do not have rotating magnetic fields. Rather, there are fixed magnetic field axes for the field (direct axis) and armature (quadrature axis). Even though the armature is rotating, the magnetic field axis in the armature is fixed thanks to commutation, which allows the direction of current in an armature conductor to change as it passes from the region under one main field pole to the next.

A diferencia de sus homólogos de CA, las máquinas de CC no tienen campos magnéticos rotativos. Más bien, existen ejes de campo magnético fijos para el campo (eje directo) y la armadura (eje en cuadratura). Aunque la armadura esté girando, el eje del campo magnético de la armadura está fijo gracias a la conmutación, lo que permite que la dirección de la corriente en un conductor de la armadura cambie a medida que pasa debajo de un polo de campo principal al siguiente.

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

Relevant standards including IEC 60085 and IEEE 1 have similar definitions for electrical insulating materials (EIM) and electrical insulation systems (EIS). As with any system, there is an interaction between the materials used, and the insulation system developers take great care to ensure that this interaction does not lead to undesirable outcomes.

Diferentes normas relevantes incluyendo la IEC 60085 y la IEEE 1 definen de forma similar los materiales electro aislantes (EIM) y los sistemas de aislamiento eléctrico (EIS). Como en cualquier sistema, existe una interacción entre los materiales usados y los diseñadores de los sistemas de aislamiento cuidan todos los detalles para evitar que esta interacción produzca resultados indeseados.

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!

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

This inspection report helps record a DC motor's connection as it enters the service center. It is intended for use with 2-, 4- and 6-pole DC machines.

The Institute of Electrical and Electronics Engineers (IEEE) standard for insulation resistance testing of motor and generator windings that was published in 2002 has been revised. The 2013 edition was published in March 2014. This article examines the changes to the standard.

We know that excessive temperature and moisture are the largest contributors to bearing and winding failures. Understanding the source of the increased temperature will help us to correct the problem and improve the machine’s life expectancy.

A conversation with two EASA members led to a method for determining whether the interpoles are connected with the correct number of circuits. Not only is this method easy, it's a refinement of the interpole polarity test we routinely perform on every repaired DC machine.

Have you ever wondered about the purpose of the shims found under the interpoles in most DC machines? Those shims are used by the manufacturer to adjust the interpole strength. If they are lost, left out or mixed up, the result will be a DC motor or generator that arcs - especially when loaded.

Covers all necessary steps for layer-winding DC field coils, how to layer-wind a shunt field coil, how to reinsulate an interpole field coil, and how to install large field coils in the frame.

Illustrates procedures for manufacturing random-wound interpole and main field coils for DC machines. Covers everything from removing old coils and taking data to installing and connecting new coils, including how to construct winding forms and jigs, how to shape coils to conform with the curvature of the field frame and how to insulate field coils. Both “wet” and “dry” winding techniques are illustrated.