METREL MI 3399, Инструкция с упражнениями

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Power and Voltage Quality Trainer AD 2
– MI 3399
176
4.5.3 Capacitive, switching and nonlinear load
In this step we will introduce capacitive load on phase L1, switching load on phase L2
and nonlinear (harmonic) load on phase L3. First, set switches S1 ÷ S11 on Application
Trainer
as shown in table below. This will introduce 15º phase lag on phase L1,
switching current on phase L2 and harmonics on phase L3.
Switch Description State
S4 Capacitive load & Energy
ON
Figure 4-53: Power generated on second phase
Capacitive load can be seen on phase L1 (negative values for N and Q, and suffix “c”
on Power Factor) as shown in the figure below.
Figure 4-54: Capacitive load on phase L1
On phase L2 a switching load is present, which turns on and off every 10 seconds.
Rec interval (n-1) Rec interval (n+1) Rec interval (n)
Time (s)
Current (A), Power (W)
1000A
10
20 30 40
50
60
Active average (AvgOn ),
average measured in (n) interval
only when I≠0A
Minimal value
during (n) interval
Maximal value
during (n) interval
Average value during (n) interval
Figure 4-55: Switching load presented on phase L2
Current profile is shown in the graph above. Note that recording interval (1min) is
longer than load switching frequency (10sec). What we see on the instrument is:
- METER screen: Real time power measurement (refreshed few times per
second). Values are changed every 10 seconds, as load is turned on and off.
- TREND screen: power averaged over a 1 minute time interval.