IEC61000-3 S
OFTWARE FOR
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M
ANUAL
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IEC61000-3?
V
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NSTRUMENTS
VPN
98-025/7
P
AGE
7
As an example, the simple rectifying circuit seen at the input to many
switch-mode power supply designs presents a highly distorted load, which
draws current only at the peak of the voltage waveform.
Distorted current waveforms are undesirable because they can lead to
several problems in the ac supply. Examples include: reduction of power
factor, causing excessive heat losses in the transmission cables, and
excessive neutral currents in balanced three phase systems; and distortion
of the supply voltage, which may interfere with other equipment using the
same supply.
In the particular case of the switch mode power supply example shown
above, IEC61000-3-2 would impose limits on the amplitude of each
harmonic of the current.
Another subject covered by the IEC61000-3 specifications is fluctuations in
load.
Nowadays, more and more products are incorporating controls such as
timers and thermostats, which can cause frequent changes to the load seen
by the supply. Examples are cooking appliances, heaters air conditioners
and photocopiers.
L
AC
Supply
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Voltage
Current
Summary of Contents for PM3000ACE
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