Application Note
No. 104
Technical
Application Note
Overview of Power Conditioning Technologies
understanding the differences between technologies. For a more
complete description of these devices consult Leviton’s Power
Quality Reference Guide.
Power Quality
Below is a simplified description of the most commonly used
power conditioning devices based on the IEEE Emerald Book.
This is meant toprovide a very basic reference frame for
Selection Guide to Power Conditioning Technologies
Surge
Protection
Device
Surge
Common Mode
Normal Mode
Noise
Common Mode
Normal Mode
Noise Filter
(EMI/RFI)
Line
Conditioner
(Isolation
Transformer)
Voltage
Regulator
Standby
Power
System
UPS
Standby
Engine
Generator
✔
✓
✔
✓
✓
✔
✓
✓
✔
✓
✔
✓
✔
✓
✓
Sag
Swell
Undervoltage
Overvoltage
✔
✓
✔
✓
✔
✓
✔
✓
Momentary Interruption
✔
✓
✔
✓
✔
✓
✓
Long-Term Interruption
✓ Leviton Products
✓
✓
The level of resolution to power problem will vary from manufacturer to manufacturer
R
*Note: See the back side of this Application Note for an IEEE description of each technology.
Leviton Mfg. Co., Inc.
59-25 Little Neck Parkway, Little Neck, NY 11362-2591 • Techline 1-800-323-8920 • Fax 1-800-823-9538
Visit our Website at: www.leviton.com
1
Technical
Application Note
Application Note
No. 104
..........................
Summary of Power Conditioning Technologies
Device and Principal Functions
General Description
Surge Protection Devices
Divert or clamp surges.
Various types of surge suppressors are available to limit circuit
voltages. Devices vary by clamping voltage, and energy handling
ability. Typical devices are “crowbar” types like air gaps, gas
discharge tubes; and nonlinear resistive types like thyrite valves,
avalanche diodes, and metal oxide varistors. Also available are
active suppressors that are able to clamp, or limit, surges
regardless of where on the power sinewave the surges occur.
These devices do not significantly affect energy consumption.
Noise Filters (EMI/RFI)
Common or transverse-mode noise reduction with attenuation
and band-width varying with filter design.
Line Conditioners/lsolation Transformers
Line conditioners often provide both isolation and noise
reduction. Some products provide multiple noise-reduction
methods, e.g., transformer and filter, but no regulation.
Isolation transformers attenuate common-mode disturbances on
the power supply conductors. They provide a local ground
reference point. With taps, allows compensation of steady-state
voltage drop-in feeders.
Voltage Regulators
Provide a relatively constant steady-state output voltage level for
a range of input voltages.
Standby Power Systems (Battery-lnverter Type)
Inverter and battery backup, operating as UPS, when normal
power fails. In standby mode, the load is fed directly from
the utility.
Uninterruptible Power Supplies (UPS)
Maintain supply of regulated voltage, waveshaping, noise/surge
violation for a period of time after power failure.
Motor Generators
Voltage regulation, noise/surge elimination, and waveform
correction for voltage distortion.
Series inductors with parallel capacitors. Good for
low-energy, high frequency noise.
Shielded isolation transformers or shielded transformers with
surge suppressors and filters.
Transformer with physically different winding for primary and
secondary. Often has single or multiple electrostatic shields to
further reduce common-mode noise.
A variety of voltage regulation techniques are utilized. Common
techniques include ferro-resonant transformers, electronic tap
switching transformers, and saturable reactor regulator.
An inverter to which the load is switched after utility failure.
There is some break in power when the transfer to and from
utility power occurs. Usually comprised of a solid-state inverter,
battery, and small battery charger.
Line interactive or rectifier/inverter technologies are most
common. A battery supplies the power to the inverter during
loss of input power.
Most often two separate devices, a motor and an alternator
(generator), interconnected by a shaft or other mechanical
means.
Other Miscellaneous Devices
Harmonic Filters
Reduction in input current harmonics of non-linear loads, which
can cause heating of power conductors, transformers, motors,
etc.
Series inductors with harmonic trap to prevent harmonics from
being fed back to line.
Source: IEEE Std. 1100 (Emerald Book). Recommended Practice for Powering & Grounding Electronic Equipment
Leviton Mfg. Co., Inc.
59-25 Little Neck Parkway, Little Neck, NY 11362-2591 • Techline 1-800-323-8920 • Fax 1-800-823-9538
Visit our Website at: www.leviton.com
2
C-667/G3-eg