Variable frequency drives (VFDs) are more common than ever before.  Sometimes when a VFD is introduced into a motor driven system, system reliability suffers. This recording addresses some of the common factors that reduce motor driven system reliability and how to correct them.   

Revised September 2022!
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In today’s global economy, it is quite possible to get electric motors from all over the world. Most electric motors that are 500 hp (373 kW) or less will conform to one of two basic manufacturing standards; NEMA or IEC. The intent of this article is to focus on IEC standards for managing voltage stress in VFD applications as it pertains to the motor’s windings.

En la economía global actual, es posible adquirir motores eléctricos fabricados en todo el mundo. La mayoría de los motores eléctricos de 500 HP (373 kW) o menos se ajustarán a una de las dos normas básicas de fabricación; NEMA o IEC. La intención de este artículo es centrarse en las normas IEC para gestionar la sobre tensión en aplicaciones con VFD en lo que respecta a los devanados del motor.

This webinar goes through the basics of what accessories may be needed for proper VFD control and power quality add-ons to improve motor driven system reliability.

Revisit EASA's 2021 Convention & Solutions Expo by buying access to recordings of the general sessions and education events streamed from EASA's website! These recordings provide just over 22 hours of training. Downloadable PDFs of slides and technical papers are included!

This webinar recording reviews the failures associated with 3-phase motors on Variable Frequency Drives (VFDs) and how to rewind to limit future failures.

This webinar recording explains the basics of low voltage AC drive types and control methods.

Here is a random collection of some relatively common misconceptions about three-phase squirrel cage motor performance characteristics.

Aquí tenemos una colección de algunos de los conceptos errados más comunes acerca de las características de desempeño de los motores eléctricos tipo jaula.

While adding variable speed capability in commercial buildings is not a new idea, a new analysis confirms major energy and cost savings is available by pairing those products with a power drive system (PDS) – regardless of a pump’s load variability. A PDS combines an electric motor, adjustable speed controls and sensors that provide feedback to the equipment, allowing the equipment to slow down or speed up to meet current demand. This idea and the added flexibility a PDS can provide may be even more important as we move forward in uncertain times.

A special discounted collection of 7 webinar recordings focusing on various aspects of electromechanical repair.

Just $35 for EASA members!

This webinar explains what shaft currents are, what causes them, and differentiate between the two common causes. It also discusses and compares methods to mitigate shaft currents and explains why the different causes of shaft currents require different solutions.

This manual covers horizontal and vertical squirrel-cage induction motors in the 300 to 5,000 horsepower range, low- and medium-voltage. Most of the principles covered apply to other sizes as well. This manual focuses primarily on IEC motors and standards.

Induction motors are most often applied to what are essentially constant speed drive applications. However, the use of induction motors in variable speed applications continues to grow, primarily due to technology advances in power electronics. This webinar will review speed control basics for induction machines.

Las versiones impresas y en forma de descarga del valioso manual didáctico / recurso de EASA, “Principios de Motores C.A. Medianos y Grandes”, se  ahora disponibles en inglés y en español. El manual incluye gráficos e ilustraciones, fotografías y mucha información técnica sobre máquinas C.A., incluyendo como funcionan, información específica sobre los tipos de encerramientos, fabricación de componentes y aplicaciones.  Muchos de los principios incluidos en el libro aplican a todos los motores C.A., especialmente a aquellos accesorios que fueron asociados en el pasado con las máquinas más grandes (como encoders, RTDs, termostatos, calentadores de espacio, sensores de vibración, etc.).

On October 22, 2018, the European Commission submitted its plan to expand motor and power converter efficiency regulations. As part of the EcoDesign directive, the Commission has been working on expanded motor and drive regulations for several years. The European Union directive will address both motors and variable frequency drives (VFDs) from .75 to 1,000 kW (1 to 1340 hp).

There are a few areas of concern involving the misapplication variable frequency drives (VFDs) on a standard induction motor. This article looks at some of those.

There are several methods to operating a three-phase motor using single-phase power to make what would be an otherwise expensive and arduous process a little easier.

We all have that occasional customer who got a “deal” at an auction: a compressor, or lathe, or wood-working equipment, only to discover when he started to install it that this equipment has a three-phase motor and only single-phase power is available. You know that you are about to be called upon to “convert” that piece of equipment, and you probably realize that it’s going to cost you more than you can charge.

Todos nosotros tenemos ese cliente ocasional que compró “una ganga” en una subasta, como un compresor, un torno o una máquina para trabajar madera y que solo descubre al comenzar a instalarlo que ese equipo tenía un motor trifásico y que él dispone únicamente de energía monofásica. Posiblemente sea su vecino o un amigo de la iglesia. En cualquier caso, usted está a punto de ser contactado para “convertir” esa parte del equipo y probablemente piensa que eso le va a costar más de lo que el puede gastar. Soluciones utilizadas anteriormente incluyen​: Conectando dos fases a los 220 voltios de la entrada monofásica y condensadores a una de las líneas energizadas para crear “una línea fantasma” para el tercer cable. Utilizar un convertidor de fase rotativo. Descargar el artículo siguiente para los detalles.

With the growing popularity of variable frequency drives (VFDs), it is likely almost every EASA service center has repaired motors powered by one in a customer’s installation. For these motors, it is best that after repair they are tested using a VFD, typically at no-load. This will provide operation mimicking the actual customer application, at varying speeds, and will help ensure proper mechanical operation throughout the speed range. This will include detecting vibration problems, identifying any resonant speeds within the operating range, and more. Also, if the motor is used above utility line frequency (i.e., 50 Hz or 60 Hz), it should be operated up to top speed for vibration measurement and a good break-in of the bearings.

Topics covered include:

• Selection challenges
• Voltage, power rating and frequency
• New or used VFDs for testing?
• Operating parameters

Con el aumento de la popularidad de los variadores de frecuencia electrónicos (VFDs o drives), es probable que casi todos los centros de servicio miembros de EASA hayan reparado algún motor que funcione con un variador de frecuencia en las instalaciones de un cliente. Lo más conveniente después de reparar estos motores es probarlos, generalmente en vacio, utilizando un drive. Esto nos permite simular la aplicación real del cliente variando la velocidad así como también tener la certeza que el motor funciona bien mecánicamente dentro de un rango de velocidades. Esto incluye descubrir problemas de vibraciones, identificar alguna velocidad de resonancia dentro del rango de operación y otros problemas. Además, si el motor está trabajando por arriba de la frecuencia de red (ej. 50 ó 60 Hz), deberá funcionar hasta alcanzar su velocidad máxima para comprobar sus niveles de vibración y que los rodamientos puedan expulsar el exceso de lubricación y se asienten por sí mismos en su posición de trabajo (break-in). Los temas cubiertos incluyen: Desafíos de selección Tensión, potencia y frecuencia VFD nuevos o usados para las pruebas? Parámetros de operación

This article describes the technical issues in online partial discharge (PD) detection on motors fed by VS-PWM drives, and gives an example of one system that detected the PD successfully.

This manual, a companion to EASA's 2-day seminar of the same name, covers horizontal and vertical squirrel-cage induction motors in the 300 to 5,000 horsepower range, low- and medium-voltage. Most of the principles covered apply to other sizes as well. This manual focuses primarily on NEMA motors.

Modern variable frequency drives (VFDs) offer an almost dizzying range of capabilities that include output frequencies into the hundreds of hertz. It can be tempting to use a standard AC induction motor with one of these VFDs. But doing so requires a thorough understanding of the intended application and how the VFD will affect the motor. Since the most popular VFDs sold today are pulse-width modulated (PWM) type, the comments and recommendations in this article will assume that is the type used. Also, motor voltage will be 600 volts or less.

Shaft currents have always been a concern for large motors due to magnetic asymmetries within the motor. Manufacturers strive to keep these to a minimum.  With the widespread use of Variable Frequency Drives (VFDs), shaft current issues have become a concern in all sizes of motors. If these currents are discharged through the bearings, electrical discharge machining (EDM) occurs. Proper installation of VFDs can play a large part in mitigating issues with shaft currents. 

No-load testing of repaired motors is common in most if not all repair service centers. ANSI/EASA AR100-2010 Recommended Practice specifies, “for AC motors, no-load running tests should be made at rated voltage and rated frequency.” For sine-wave powered motors, this statement is straightforward. For motors used on variable frequency drives (VFDs), there are a number of possibilities service centers may employ with the motor supplied by line (utility) power, and in some cases the tests may be less than ideal. 

This paper, originally presented at the 2014 EASA convention, deals with understanding IEEE Std 519 and various mitigation methods in order to meet those recommendations. It also reviews the types of filtering that is available to reduce the reflected waves, first turn insulation stress, and common mode voltages seen at the motor terminals.

Whenever an application engineer is planning on installing adjustable speed drives for AC motors, line current harmonics and reflected waves are two factors that need to be addressed. This paper, presented at the 2013 EASA Convention, deals with understanding IEEE Std 519 and various mitigation methods in order to meet those recommendations. It also reviews the types of filtering that is available to reduce the reflected waves seen at the motor terminals.