Variable Speed Drives (VSD) vary the frequency of the power delivered to the ESP motor, thereby changing motor and pump RPM, allowing production volume flexibility. COSCO can provide a number of VSD packages including:

  • Low Voltage VSD’s
  • Medium Voltage VSD’s
  • NEMA 1, 3R, 4, or 4X enclosures
  • Skid mounted or building enclosed packages
  • Air conditioning or liquid cooling available for high ambient temperature applications
  • Allen Bradley Power Flex series are standard equipment
  • Other brands also available

VSD’s can damage system insulation, shortening ultimate run life of the ESP installation. Therefore, the technology utilized is of significant importance if variable speed capability is required.

Allen Bradley VSD’s offer near sine-wave outputs with low harmonic content resulting in better motor performance and extended motor and cable run life.

In some cases, input filters and sine-wave filters are also employed.


Example of near-perfect sine-wave form produced by Allen Bradley Series 7000 Medium Voltage VSD


Allen Bradley Power Flex 7000 Series Medium Voltage VSD’s utilize advanced power conversion technology with Current Source topology using an active front–end called a Pulse Width Modulated Rectifier (PWMR). This eliminates the need for a multi-winding transformer to mitigate unwanted harmonics.

Step up transformers to provide motor voltage are eliminated in most cases, since the MV drive can output motor voltage. Besides being motor friendly and cost effective, reduced space requirements are an added benefit, particularly important in offshore applications.

Allen Bradley Power Flex 700 Series VSD’s are available for low voltage (480 V) applications.

A step up transformer is utilized to deliver motor voltage.



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