ALL MOTOR PROBLEMS

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Applications

Successful applications of polyphase machines require an understanding of electrical machine and loading operation to make an economic and productive equipment for the user.  Most large equipments have survived the installation and initial operation with the support of the original manufacturers.  

  • When the user’s requirements change and equipment must be re-rated, modified or up-dated very often the original manufacturers are no longer in the business or the original application engineer is no longer available.
     
  • An update of the control equipment (switchgear) can require input data for sizing or settings that is no longer available.
     
  • Conversion of existing equipment to new power sources (such as an adjustable frequency drive) can require a new skill set and an understanding of the original application.

AC Motor Technologies, Inc. has provided technical support for the re-rate, upgrade, and modernization of existing equipments. For example:

Up grade of vertical pump motors to new adjustable frequency drives

Several large synchronous vertical pump motors had operated for several years with a current source inverter adjustable frequency drive.  The starting performance was difficult and didn’t always accelerate, the full load performance was limited by the drive rating as there was no overload capability.  This resulted in many shut-downs of the equipment during what should have been “normal” operation

AC Motor Technologies, Inc. worked with a drive consultant and equipment installer to provide a system capable of increasing the motor/drive performance by utilizing an IGBT drive and an improved power supply.  This provided the required performance and capabilities to increase the availability of the motors and eliminated unscheduled shut-downs. 

During this project, the existing motors were refurbished, tested, and provided with modern high frequency protection for their bearings.
 
Synchronous Motor Switchgear Replacement

A municipal application included several brushless synchronous motors which were started at a reduced voltage.  The mechanical parts of the 40+ year old equipment need replacement.  AC Motor Technologies, Inc. configured the replacement equipment which now included a modern solid-state motor control center and synchronous motor controller.  The equipment was ordered and installed by a local contractor to the specifications.

The start-up went smoothly, including the integration of load and motor functions. 

Mill up-rate

A mill operator had re-rated one Wound-Rotor motor in a Tandem pair.  They user wanted confirmation that the motors were operating correctly and sharing the load.  Because of the change in the Torque vs speed with the up-rate, the motors would not share load directly as their ratings might indicate.

AC Motor Technologies, Inc. reviewed the old and new designs and explained how the tandem motors would share the load and the means to achieve loading in accordance with their ratings.

AC Dynamometer Drives
A change in testing needs required higher speed dynamometers at an automotive testing center.

AC Motor Technologies, Inc. worked with a motor repair center to review the AC Motor design and ascertain that the shaft critical speed would still be above the new running speed.  Suggestions were also given on testing for the motor repair center to achieve the higher speeds to confirm the higher speed operation.

Reconfiguring ventilation for a 4-pole induction motor

The re-application of a 4-pole motor required a revised ventilation system to convert a water-cooled motor to a forced-air cooled motor, with air drawn from outside of the local environment.

AC Motor Technologies, Inc. reviewed the motor installation on-site and configured enclosure modifications to make the change.  The enclosure hardware was manufactured by a local motor repair shop and combined at the site with the necessary ducting and blowers to pressurize the motor enclosure while providing the required cooling air.

Starting Performance

AC Motor Technologies, Inc. has developed a motor simulation computer analysis that illustrates the starting performance of a Synchronous Motor and Brushless Exciter which can help to analyze Starting issues that can occur when loading or equipment changes are made.   This technique shows the motor operation and the effects of reduced voltage as well as load magnitude and inertia changes.  This helps to define the start-up timing sequence and control function settings for maximum performance

                                                                                             Figure-1

                                                                  MOTOR STARTING PERFORMANCE SIMULATION

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