Hi, my name is Simran Nanda and I am an R&D Engineer at Keysight Technologies. Today I
will be showing you the filters on the PA2203A IntegraVision Analyzer. What I have here is
a VFD driving a 3-phase motor. I will be looking at just the voltage waveform. First off, you
can see the voltage waveform up top. If you stop that – and it is hard to trigger on
– but if you zoom in, you can see what it is actually made up of is a PWM signal. It's
a 2-level PWM signal. To be able to see the fundamental of that signal, what you can do
is turn on filters. Go to the filter menu, channel 1, voltage filter. You have a selection
of high pass and low pass filters at some cardinal points. I am just going to pick the
1 KHz filter just to see the effect that it has. You can see with the 1 KHz
digital filter in line with the measurement the PWM signal has turned into the fundamental
sine wave that the device most likely sees. Depending on the actual low pass filtering
of the device you may see something different, but this makes it easy to trigger on the signal;
much easier than on a PWM signal coming out of the VFD directly. Now I am going to switch
over to the function generator. Now I have my function generator hooked up generating
a square wave on both V1 and V2 inputs of the analyzer here. I just wanted to show you the
effect of the filters on a square wave. I can zoom in here. You can only see – let's
back up a little – only one waveform, but really there are two; they just are identical
so they look like they are sitting right on top of each other. I will go to channel 2
voltage and turn on the filter. Let's start with the 100 KHz. You can see the
higher frequencies have been filtered out so the rising edge is not as sharp. I'll keep
going with that, and let's just walk through some of these filters. The thing to notice
here is the two channels do stay lined up. Since it is a digital filter we can take out
the delay that the filter adds to make sure the channels stay lined up, which is important
for phasors and for power calculations in general. If you have any skew setup that you
takes out the skew of the wiring; the filters won't interfere with that. Now,
let's switch over to a sine wave just to show you the filter response. We will do a sweep
from 10 Hz to 500 KHz. Let's see; I'll move this guy over. We'll turn the sweep
on. Again, you can see the yellow is channel 1, which isn't being filtered, and the green
is the channel that is being filter. The 200 Hz filter you can see the roll-off. As you step
through these filters you can see the effect that it has. We won't go through all of them;
we'll just jump to the 100 KHz, get it on the screen. There
you can see it passes most of the frequencies and up near a 100 KHz cutoff being
right about there it rolls off. The other interesting thing, again, to notice is that
the filters do stay lined up. So, if I zoom in here, even as we're sweeping and filtering
the signal, the two lines do stay in sync. In summary, we looked we at the filters on
a real application, which was the VFD feeding an AC motor and saw the advantage of using
the filter so it makes the waveform easier to trigger on, and it kind of simulates what
the actual motor is going to be seeing. We also looked at if you sweep an input simple;
we looked at the characteristics of the filters.