Even Greater Energy Savings With Baldor Drives

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Even Greater Energy Savings With Baldor Drives
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Opportunities With Drives

• Proper Use of Drives Can Save Energy ()
• How to Identify and Evaluate Potential Drive
  Applications
• The Fan Laws (Pumps also)
• The Cube Rule

230.6
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Possible Energy Savings With Drives Variable
Loads
Air conditioning
20-25 Compressors 20-25 Central
refrigeration 25-35 Blowers and fans
30-35 Feedwater pumps 30-50
Source Wisconsin Center for Demand-Side Research
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Cube Rule

• When using a variable speed drive and motor on a
  centrifugal application
• The flow is directly proportional to motor speed
• The required torque varies as a square of the
  speed
• The required horsepower varies as a cube of the
  speed
• The energy requirement is proportional to the
  horsepower
• Therefore, the energy varies as a cube of the
  speed

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Fan Law - Cube Rule
100
75
Fan or Pump Load Curve
LOAD
50
25
Power Speed3
0
0
25
50
75
100
SPEED
FLOW
110.8.6
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Example centrifugal pump driven by a 10 hp. 4
pole motor. Torque HP5250/rpm30 lb.-ft _at_
1750 rpm.

• Use an inverter to slow down 20 from 1750 to
  1400 rpm.
• Torque required(1400/1750)2 .64 x 30
  19.2lb.-ft.
• Horsepower required((19.2x1400)/5250) 5.12hp.
• This shows that torque required changes in
  proportion to the change of the speed squared.
• Horsepower required (1400/1750)3 .512 x 10
  5.12 hp.
• Also, this shows that the horsepower required
  changes in proportion to the change of the speed
  cubed.

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Characteristics of Good VSD Applications

• High Annual Hours of Operation
• Moderate to High Horsepower
• Variable Load (high degree of throttling)
• and/or
• Process Improvement from Improved Control

160.26.0
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VSD Application Evaluation

• Information Needed
• Motor Nameplate Data (Horsepower Voltage)
• Pump / Fan Nameplate Data
• Annual Operating Hours
• Load Duty Cycle

160.26.1
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VSD Application Suggestions

• Choose the highest payback applications
• Use a system integrator to evaluate the total
  application
• Use feedback device to maximize performance
• Integrate into plant operations
• Consider cost of engineering, installation,
  start-up