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Newsletter 2004 issue 2 |
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Control Your Motors
Variable frequency drives (VFDs) on motors
can enhance process operations, especially for flow control,
and can efficiently cut energy demand for pumps and fans.
Motors are sized to fit a maximum load and
operate at a constant speed. But, demand on motors fluctuates.
Greater power is needed at start-up; air pressure changes
in a paint booth because doors are opened; more-viscous product
is pumped through process lines.
VFDs control the difference between supply
and demand by automatically matching the motor speed to the
actual needs of the system based on input from sensors. VFDs
control motors more efficiently than throttling or other means,
which reduces energy bills.
VFDs in use
Kerry Bio-Science added a VFD for flow
control when automating its sterilizer. Before, more-viscous
product couldn’t reach the tank fast enough. When this
affected process time and temperature, product was diverted
to the sewer as waste. Now, the VFD maintains a constant flow
rate.
Crestliner, an aluminum boat manufacturer,
ordered a VFD for its new paint booth to extend filter life
and cut energy costs. As paint accumulates in the filters,
the VFD automatically adjusts air flow to maintain the exhaust
rate for the booth. Filters are now changed less frequently.
Ask your electric company about rebates
for VFDs.
Background
Adjustable Speed Motor Drives—the
Basics
This energy efficiency fact
sheet by the Washington State University Cooperative Extension
Energy Program provides a primer on adjustable speed motor
drives.
ASDMaster Software
Adjustable Speed Drive Evaluation Methodology and Application
Software
is a Windows program that helps plant and operations professionals
determine the economic feasibility of an ASD application,
predict how much electrical energy may be saved by using an
ASD and search a database of standard drives. Purchase through
the Electric Power Research Institute (EPRI).
Understanding Variable
Speed Drives
This article in EC&M
magazine for electrical engineers describes how to match
the VFD to the motor's driven load.
Application Examples
Air and Water Flow Control
Varying electric motor speed can significantly reduce energy
waste for air and water flow control (e.g., circulating water
systems and pumps, injection-molding equipment, cooling towers).
See this Alliant
Energy Web page.
Air Supply
Office Buildings/HVAC. Based
on Xcel Energy's recommendations, building
management for Campbell Mithun Tower, Minneapolis, upgraded
inefficient motors to NEMA Premium efficiency motors and installed
adjustable speed drives (ASDs).
Optimizing Electric
Motor Systems at a Corporate Campus Facility. 3M evaluated
approximately 1,000 electric motor systems for energy saving
opportunities. Among other actions, VFDs were installed in
two different areas on fans for air supply. U.S. Department
of Energy case
study.
Paint Spray Booths
Variable Frequency Drives for More
Efficient Manufacturing Operations. In paint spray
booths, VFDs increase fan speed, and thus the supply air
CFM, to compensate for the loss of air through the open doors
to control booth pressure. A VFD allows for automatic compensation
for filter loading.
Pumping
Dairy Farms. Variable frequency
drives on milking
vacuum pump systems of dairy farms offer an excellent
energy conservation opportunity.
Variable Speed Pumping—A
Guide to Successful Applications, Executive Summary
is a tool to assist plant owners and designers as well as
pump, motor, and drive manufacturers and distributors to help
determine whether variable speed pumping
is the correct choice.
Refineries
Motor System Upgrades Smooth the Way
to Savings of $700,000 at Chevron Refinery. The pumps
on the refinery's
diesel hydro treater were oversized. VFDs reduced energy use.
Wastewater Treatment
Facilities
Energy Success Case Study. Pumping
and aeration account for a majority of energy consumption
in wastewater facilities. This Iowa Energy Bank Program case
study outlines the use of VFDs at wastewater facilities.
Water and Wastewater Facilities.
Variable-frequency drives are enjoying rapidly increasing
popularity at water and wastewater facilities, where the greatest
energy draw comes from pumping and aeration. More information
is this California Energy Commission document.
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