Technical articles: variable frequency Drives

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HARMONY PROTOPS DISCUSSION

Medium Voltage Variable Speed Drive, The Perfect Harmony Advantage, Systems Process Availability

Power quality and process efficiency are both important considerations in the selection of VFD systems. It is equally important that the systems provide the highest available level of process availability.

The Perfect Harmony product, with its distributed cell power architecture, provides a unique platform to deliver the highest levels of process availability.

USING VARIABLE FREQUENCY DRIVES ON PUMPS SYSTEMS

Variable Frequency Drives (VFDs) on pumps offer many advantages over traditional methods when it comes to constant pressure control. They cost less than water towers, offer precise pressure control, reduce water leakage, increase pump life and save energy.

Traditionally, water towers or ground/ underground reservoirs equipped with pumps are used for water storage and maintaining pressure in the distribution systems. Mechanical devices such as control valves are used to regulate pressure. These methods have disadvantages when it comes to operation, flexibility and energy consumption. Water towers can be an expensive choice when it comes to maintenance and system upgrades. Selecting the wrong control valves can significantly reduce pump efficiencies and could lead to routine maintenance problems. With the proper design, VFD technology offers solutions to these problems.

A VFD is an electronic controller that adjusts the speed of an electric motor by modulating the power being delivered. VFD and pump combinations maintain a constant pressure in the system by taking 4-20 mA signal from a pressure transmitter and adjusting motor output according to the feedback requirements. VFDs overcome the disadvantages of traditional methods mentioned earlier and offer many benefits-increased pump life, precise pressure control, reduced water leakage, easy upgradability and energy.

TECHNICAL OBSERVATIONS ON THE INPUT/OUTPUT CURRENT OF THE PERFECT HARMONY DRIVE

Although it seems counter intuitive, it is possible for the output current of a voltage source drive like the Harmony to be greater than the input current. This is a result of the topology of the circuit and the behavior of the switching devices on the output.

LIQUID-COOLED PERFECT HARMONY. COOLING SYSTEM

The standard liquid-cooled Perfect Harmony drive utilizes a pressurized, closed-loop cooling system where coolant circulates between the drive input transformer/power cell heat sinks/residual heat exchangers and a liquid-to-air or liquid-to-liquid heat exchanger.

FAILURE ANALYSIS ENGINEER RELIABILITY DOCUMENT FOR PERFECT HARMONY VARIABLE FREQUENCY DRIVE

This document applies to the Perfect Harmony Variable Frequency AC Motor Drives (VFD) configured from three through six power cells. The development of this document was intended as a source of reference for the overall Reliability, Availability, and Maintainability of the Prefect Harmony.

Siemens drives picked for BP's deepwater program

New Kensington, Pa.  Low- and medium-drives manufacturer Siemens was recently awarded a strategic contract with BP for up to $12 million for its Gulf of Mexico Deepwater Development Program.