Power Quality and Drives LLC

Welcome To Power Quality and Drives LLC


Visit Our Industrial Products Store

Variable Frequency Drives, Electric Motor Starters, Contactors, Motor Overload Relays, Duplex Pump Controls, Surge Suppressors, Pressure Transducers are available for purchase.

For items not listed in our store, please contact us with specifications for price quote and delivery.

Variable Frequency Drives

General Specifications for LS Industrial Systems 

User Manuals for LS Industrial Systems VFDs

Technical Presentations on Motors and Drives that address

Power Quality and "Failed Application" Issues:

Power Quality is an important factor in maintaining production output in every industrial facility. In addition to loss of production due to equipment shutdown, product quality may also be affected when equipment continues to operate under poor power quality conditions. It is therefore not sufficient to merely keep equipment operating through power disturbances, but rather, it may also be necessary for some processes to engage in an orderly shutdown when a disturbance occurs.

In addition to power quality problems, other important factors in maintaining industrial production is both the avoidance and correction of improper applications of adjustable speed drives.

An adjustable speed drive that is not functioning properly is often not in need of repair. It may be found to have some problem with the incoming power source, the signal and power wiring technique, the programming, or perhaps the drive has not been specified properly for the application.

Thus, if a drive is turning the motor and the service personnel can not effect a repair, the problem may not be a "failed drive" but, rather, it may be a "failed application."

System considerations that affect the performance of a drive are indeed often overlooked. Power Quality and Drives presents information needed to help resolve the "failed application" problem. Other power quality related topics addressed are: Starting currents and torques of reduced voltage starters are compared to those of variable frequency drives. Wiring techniques to reduce or resolve EMI/RFI problems, effects of short circuit capacity on drive application, transformer sizing, selection of current limiting fuses, and variable speed drive application for regenerative and overhauling loads.

Please return to the Power Quality and Drives LLC home page often for the latest topics.

Our Store Includes:

Ride Through on Power Sag or Power Loss
Rotary power supplies for use with variable frequency drives are available that will allow ride-through of the drive for up to five seconds after power sag or power loss.

Motor Protection: Preventing the Burn-out
Enhanced motor protection will not only lower motor rewinding and repair costs but will also lower over-all down time and yield an increase in production.

Suppressor Technology: Surge Amps, Clamping Volts and Equipment Protection
Compare the clamping volt ratings at the 40,000 and 60,000 Surge Amp levels of the Model LA603 with the ratings of units of other manufacturers.

Variable Frequency Drives Seminar: Problems Encountered and Basic Mitigation Techniques
A seminar on the basic problems that are caused by VFDs is offered by Power Quality and Drives LLC.

Products of the Month

Power Quality

AC Drives and EMI/RFI Mitigation
Ferrite cores, EMI filters, drive isolation transformers, insulated power cables, and proper grounding techniques are presented as solutions to EMI/RFI.

AC Drives and Radiated and Conducted Emissions
Electromagnetic Compatibility Filters and Common Mode Chokes

Variable Frequency Drives: Source Impedance, Short Circuit Capacity, and Line Reactors
Harmonic frequency currents generated by low horse-power rated VFDs will interact with a power source of low impedance. The resulting current flow may damage the drive's power devices.

Short Circuit Capacity: Basic Calculations and Transformer Sizing
A simplified method of calculation will allow a facility engineer or electrician the ability to estimate short circuit capacity. The application examples utilize transformer sizing for motor loads.

Variable Frequency Drives: Motor Regeneration, Overhauling Loads, and Starting Into a Rotating Motor
Many specifications call for a drive that will re-start when the driven motor is still spinning. Techniques employed by drives are presented. In nearly all HVAC applications, it is not necessary to "catch a spinning motor." Allowing the motor to coast to a stop before re-starting may provide a lower cost solution.

VFD Ride-Through On Sag and Outage
Several techniques for ride-through on power outage are presented.

Sag Correction for Small Equipment Without Using UPS Systems
Techniques are given that will allow for ride-through without the requirement of batteries and the maintenance associated with batteries.

Transient Voltage Surge Protection
Fundamentals of surge protection are presented including suppressor ratings and lead length effects.

Generators: Standby and Co-generation
Some problems may occur when drives and UPS systems are operated from generator power.

TVSS and Energy Savings?
One manufacturer of transient voltage surge suppressors is guaranteeing energy savings as a result of transient suppression. An electric utility company questions the claim.


Failed Applications

A Cogging DC Motor
A three-hundred horsepower DC motor in the paper industry was cogging. Data collected,
analysis and solutions to the problem are presented.

A VFD and Speed Fluctuations
A VFD in the food processing industry was giving erratic speed changes. Data collected,
analysis and solutions to the problem are presented.

Motor and Control Burn Out Together
Two cases histories: A control failure caused the motor to burn out in one case, and a motor
failure caused the control to burn out in another case.

An Overloaded Dough Mixer
A variety of application considerations are presented in selecting a solution to the problem.

EMI/RFI and a Magnetic Resonance Imaging Machine: A problem
created by three Variable Frequency Drives

EMI/RFI generation can indeed cause serious problems.

Overloaded VFD Due to Harmonic Current Generation
Motor nameplate amps could be within the rating of a drive. However, if the motor draws
additional harmonic current of five to six per cent then a drive that is sized marginally
may give an overload trip.

Skullduggery Afoot!
He sure looked honest!

EMI/RFI Solutions

VFDs interfered with a lonworks system

Power Quality and Failed Drives

Transients: Incoming Power Disturbance

Transients: Lightning Strike

Transients: Equipment Malfunction

Transients: The Human Factor

Transients: Disaster Averted by the Grace of God

Drive Applications

Elusive Energy Savings: Centrifugal Pumps and Variable Speed Drives - Part I

Elusive Energy Savings: Centrifugal Pumps and Variable Speed Drives - Part II

Payback Analysis for Variable Frequency Drives

Torque Capabilities of DC and AC Drives in the Constant Horsepower Range Using a Wound Rotor Motor Replacement as a Typical Application Example

Wound Rotor Control Replacement

Energy Savings: Solid-State Reduced Voltage Starters vs. VFDs

Solid-State Reduced Voltage Starters and Starting Torque

Advantages of Solid-State Reduced Voltage Starting Versus Across-the-Line, Auto-transformer and Wye-Delta Starting

Fast Acting Class RK1 vs. Semiconductor Fuses

Pump Applications

Pump Control and Protection

Variable Torque vs. Constant Torque: Ratings and Programming

Golf Course Irrigation

Motor and Drive Applications From the e-mail 

VFD with Nuisance Overload Trips

A Problem with Pump Cavitation

Positioning of Surge Suppressors, Fuses, Line Reactors and EMI/RFI Filters

Calculation of Harmonic Reduction with Line Reactors

Fuses Failed to Protect a Variable Frequency Drive

High School Science Project: DC Motor Construction

Definitions of terms used in the motor and control industry.

Visit Our Engineering Book Store

Analysis of Electric Machinery and Drive Systems, 2nd Edition

Analysis of converters used in electric drive systems, as well as DC, induction, and brushless DC motor drives.

Analysis of Faulted Power Systems

This classic text offers you the key to understanding short circuits, open conductors and other problems relating to electric power systems that are subject to unbalanced conditions.

Cable Systems for High and Extra-High Voltage: Development, Manufacture, Testing, Installation and Operation of Cables and their Accessories
The book covers in detail a range of future-oriented developments in the field of high and extra-high voltage cables.

Electrical Insulation for Rotating Machines: Design, Evaluation, Aging, Testing, and Repair
A single comprehensive resource for the design, application, testing, and maintenance of rotating machines.

Understanding Power Quality Problems: Voltage Sags and Interruptions
An in-depth analysis of voltage sags and interruptions showing how to apply mathematical techniques for practical solutions to these disturbances.

Handbook of Electrical Engineering: For Practitioners in the Oil, Gas and Petrochemical Industry
A practical treatment of power system design within the oil, gas, petrochemical and offshore industries.

Fundamentals of Fluid Mechanics
Problem solving methodology is presented using practical problems.

Links of Interest:

Technical articles on Motors, Drives, and Distribution Systems from IEEE Industry Applications Magazine 

Technical articles on Motors, Drives, and Distribution Systems from IEEE Transactions on Industry Applications 

US Government Agencies

Social Security Disability Insurance - A Timetable for Recieving Benefits 

Our Commitment to You: We're committed to bringing you the products you want at the best prices every day, and to providing you with the convenient, secure shopping experience you deserve. If you have any ideas about how we can serve you better, please contact us and we'll do our best to help. Power Quality and Drives LLC P.O. Box 83, Middlebury, CT 06762 USA (203) 217-2353 
Send e-mail by the "Contact Us" link in the upper left hand corner of the page.


Power Quality and Drives LLC
P.O. Box 83
Middlebury, CT  06762
Phone: (203) 217-2353
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