The Effects of Harmonics to Electronic
Equipment are experienced in various ways depending on the type of device -
from slight to serious consequences. Ironically, it is a known fact that most electronic
equipment is prone to misoperation due to harmonic distortion, even though it
is a harmonic generator itself. In this post, these common effects will be
briefly discussed.
Power Electronic Equipment
This equipment is reliant upon accurate
determination of voltage zero crossings or other facets of the voltage wave shape.
Unfortunately, harmonics can shift the voltage zero crossing, or the point at
which one phase-to-phase voltage becomes greater than another phase-to-phase
voltage. These are both significant points for many types of electronic circuit
controls, and the unwanted shifts can lead to equipment misoperation.
Voltage Zero Crossing Point |
Medical Instruments
Malfunctioning medical instruments
present the most serious negative effect of harmonics to electronic devices. This
is because it may place a person’s life in jeopardy. For this reason, many
medical instruments are provided with line-conditioned power and protected by
proper power quality devices.
In addition, less dramatic
interference effects of harmonics can sometimes be observed in radio and
television equipment, as well as in video recorders and audio reproduction
systems.
Computers and Other Electronic Devices
Computers and allied equipment like
programmable controllers typically require AC sources that have no more than a
5% harmonic voltage distortion factor, with the largest single harmonic being
no more than 3% of the fundamental voltage.
Harmonic distortion levels that exceed
standard limits may result to malfunctioning equipment, which in some cases,
have serious consequences. It must be noted that electronic devices can be
disturbed by the transmission of AC supply harmonics via the equipment power
supply or through magnetic coupling of harmonics into equipment components.
Moreover, other electronic instruments
can be affected by harmonics by giving incorrect data or unpredictable
performance (i.e. digital energy meters).
Voltage Notching
Most electronic devices are installed
at the low voltage level of its associated power distribution system. As a
result, they also become exposed to the effects of voltage notching. Voltage
notches often introduce frequencies, both harmonic and non-harmonic, which are
much higher than those exhibited in 5 kV and higher voltage distribution
systems.
Subsequently, these frequencies are in
the radio frequency (RF) range, which can lead into detrimental effects associated
with spurious RF, such as signal interference introduced into communication or
logic circuits. Sometimes, the voltage notching effect is of adequate power to
overload electromagnetic interference (EMI) filters and similar high-frequency
sensitive capacitive circuits.
Reference:
IEEE
519-1992. Recommended Practice and Requirements for Harmonic Control in
Electrical Power Systems
2 comments:
very great insights on harmonics to equipment. keep it up.
transmission lines
Once you've recognized that harmonics are in a circuit or in an electrical system, the next step is to carry out tests to determine the magnitude and type of harmonics.
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