User Manual

Application examples
Bandwidth. For
low power standby signals that have undesired high frequency
components, low bandwidth filters can be enabled. A low bandwidth 10 kHz filter
is available through the Setup screen under the Filter drop down option. Applying
low pass filters might vary the RMS values of voltage, currents, and power as
high frequency components affect the RMS values.
AC source. T
he IEC 62301 Standby Power full compliance test requires the AC
source to be very stable as detailed in the standard. The voltage and frequency
are required to be within 1% tolerance. In addition, the input VTHC (Voltage
Total Harmonic Content) has to be within 2% for the first 13 harmonics a nd the
VCF (Voltage Crest Factor) has to be within the 1.34 to 1.49 range. Tektronix
recommends using a stable external AC source that meets standard requirements
for the fu
ll compliance testing.
Example 5: Inrush current testing
Most el
ectrical devices draw initial current that is significantly higher than the
nominal steady state current due to low input impedance. Motor drives and
transformers are known to have inrush current twenty times higher than the
steady state currents. It is important to characterize inrush current to determine
input conductor and fuse ratings.
Measurement challenges
Accurate measurement of inrush current requires high sampling rate and no-gap
signal acquisition. It important that the correct current range is selected on the
measuring equipment while measuring the inrush current as the current can be
significantly higher than the expected steady state current.
Me
asurement solutions
The PA3000 w ith 1 MS/s sampling rate can accurately record peak signal samples
for inrush current measurements. The Min and Max hold function through the
PA3000 menu allows you to capture inrush current and other peak events on
t
he front screen. Inrush current measurements can also be made through the
PWRVIEW software. This example discusses the PA3000 setup to measure
inrush currents.
Test Setup
Complete the following steps to set up the PA3000 to take the inrush current
measurements:
Connect the DUT using a Tekronix Breakout Box (BB1000) as shown in
the wiring diagram. (See Figure 58.)
Use the 30 A shunt on the PA3000 for inrush current measurements. Using
the 1 A shunt is not recommended for inrush current because peak currents
can be quite high, even for applications where the nominal steady state
current is below 1 A.
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