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.

End users desiring speed and/or torque control often buy variable-frequency drives (VFDs) to modify existing applications where a standard induction motor is in place. Frequently, they try to control costs by using that existing standard induction motor. Before taking that path, however, it is best to consider a few areas of concern with the approach.

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.

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

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.

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.