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  • Jarrett J N. Efficacious circuit control. W.V.Ele.J. 1992 82 (39), 404-7.
  • Hewitt W R.Jr. Inverter duty in drives. J.Am.Coll. Elec. 1995. May, 44 (16), 288-9.
  • Rogers CJ. Gibney MD. Siegfried EC. Harrison BR. Glaser AC-DC inverter Am Acad Electro 1999; 41:123-7.
  • Limmer B L, Bugy L T. Artic electrical control J.AM.Podiatr Med. Assoc. 1974,69: 714.
  • Steele K, Shirodaria P., O’Hare M et al. Control box and PLM logic by way of mode of action. Br. J. Dermatol. 1989, 116;537.
  • Gloveren BG, Inverter motor application 1995, 12 (31),172-9.
  • Bunney MH, VSD system analysis New York, Oxford University Press, 1986, PP1-85.

  • Offering professionals in the oil & gas industry:
    • 24/7 technical and commercial market pricing message boards dedicated to artificial lift engineers equipment buyers. No cost registration. Users may remain anonymous.
    •Fee based independent third party commercial & technical support for operators when specifying and purchasing variable speed drives. We help oil & gas operators learn to ask OEMs smart questions to help keep you out of trouble, save you on operating expenses, and improve production. Click here to contact us for details.
    • Advanced in house or field based VSD training, customized to meet your requirements. Applications and field service installation and operating experience. Let us know when you'd like your employees to receive training targeted to what's needed. No filler, no nonsense. Learn to do your job effectively. Click here to contact us, and tell us what training is needed.


    Finally, a single place on the web to go, for artificial lift variable speed drive information and data from engineers and field installation & maintenance experts. If you're a professional with an oil & gas company, you know the value of learning unbiased data and information from actual endusers like you, without the normal commercial bias that you may get from original equipment manufacturer's (OEM) salesmen.

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    When used with VSDs, motors require to be rated for VSD inverter duty.

    Some considerations include motor operating temperature limits, which in turn means analysis of factors such as ambient temperature and altitude, load requirements and speed range.

    Ensure the motor is protected from atmospheric contamination. In addition, understand that motor cables can contribute to performance problems other than the motor insulation voltage stress concerns. Other factors include excessive voltage drop between the controller and motor, problems caused by high frequency ground leakage current and problems caused by line-to-line capacitance between the conductors of the motor cable.

    What else? ... ever wonder what the market price is for variable speed controllers? Share your oilfield equipment market information and see what your colleagues and other endusers in the industry have paid, so you know how your last purchase price matches up with other users. Registered members are free to post their equipment prices to share with others, or to inquire what price you may expect to pay! If you're a buyer or an engineer preparing an AFE, you know the value of good historical pricing information to help get your job done well.

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    About us - who we are. began operation by veterans of the oil & gas industry, who understand that good information can be hard to get.

    Our primary mission in founding ESP, - to provide a dedicated place for oil & gas engineers to get together and discuss and share their professional knowledge. Our staff and associates each bring over 25 years+ of industry experience with specific engineering and operating ESP system and variable speed drive know-how.

    Introduction - Variable Speed Drives (Controllers) in the Artificial Lift Electric Submersible Pump industry:

    Adding a variable speed drive (VSD) to an ESP system offers several advantages. VSD’s belong to a group of equipment also referred to as adjustable speed drives (ASD), variable frequency drives (VFD) or adjustable frequency drives (AFD). The operating speed of a motor connected to a VSD is varied by changing the frequency of the motor supply voltage. This allows continuous speed control. ESP systems are often designed to handle peak loads that have a safety factor. This often leads to energy inefficiency in systems that operate for extended periods at reduced load. The ability to adjust motor speed enables closer matching of motor output to load and often results in energy savings.

    Does your operation require certification such as UL-508, IEEE 519, EMC Directive, IP, & CE for onsite electrical equipment like VSD's?

    Learn how to ask the right questions and uncover any vendor abnormalities in their certification process, to understand if your ESP equipment supplier is really certified for the equipment they are supplying you.

    Safety is #1. Don't allow anything but certified equipment on your jobsite.

    Example - according to EMC Directive (89/336/EEC) article 10 part 1, the manufacturer is responsible for attaching the CE mark to each unit. According to part 2 the manufacturer is responsible for writing and updating the Technical Construction File (TCF), if the TCF route is used.

    Click here to contact us for more information, and to inquire about our pre-supply award certification and plant inspection services. Know what you are buying, before you issue that Purchase Order!

    How Does a VSD Work?

    Applying a VSD to a specific ESP application is no mystery when you understand the requirements of the load. Simply put, the VSD must have ample current capability for the motor so that the motor can produce the required torque for the load. You must remember that torque is independent of motor speed and that load horsepower increases linearly with rpm.

    A thorough understanding of how to match the VSD to the ESP driven load is the key to a successful application.

    When applied properly, the variable Speed drive (VSD) is the most effective motor controller in the industry today. Modern VSD’s are affordable, reliable and have flexibility of control.

    Electrical power is frequently transmitted to subterranean locations within boreholes to power downhole equipment, such as electrical submersible pumps (ESPs). Normally three phase electrical power is transmitted from the surface over cables running between the well casing and the production tubing. In some downhole applications, high voltage electrical power is required. For example, electrical motors for ESPs may require voltages of 1,000 to 5,000 volts at the surface. However, electrical drives capable of providing output voltages at the required level may not be available, or may not be economical even when available. When lower output voltage drives are employed in such situations, typically step-up transformers at the output of the drive are utilized to boost the voltage of power transmitted downhole.

    Effects of Power Quality

    Financial consequence : when voltage sags, productivity lags.

    The characteristics of the utility power supply can have a detrimental effect on VSD reliability.

    Harmonics produced by the VSD can have an effect on the electrical distribution and the utility system.

    The characteristics of the current & voltage produced by the VSD Inverter can cause motor problems.

    Poor power quality as it affects VSD reliability:
    •Transient Overvoltages
    •Longer term high voltage
    •Long term low voltage
    •Harmonic and current distortion

    Eliminating harmonics from your facility power system is key. A special section of the message board is dedicated to power quality. Click here.

    Step-up transformers add to the expense of the system, however, and add additional sources of failure or disturbance to the electrical system.

    Manufacturers typically cite the following benefits in the use of a VSD:

       •The most important is energy savings.
       •Accurate control and flexibility of the pump system selected
       •Linking to other automation systems
       •Reduce stress on electrical supply always start pump motor supply softly with much lower peak current
       •Harmonics reduced 12, 18 pulse
       •Reasonable investment cost
       •Natural part of control loop - eliminate deadband.
       •Reduce Maintenance Cost - ex: reduce water hammer effects caused by rapid changes in fluid throughput

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