3.8.10.6.1
Saving Results
1. With the test completed, the results and test file need to be saved to the internal
solid-state disk. To do this, press the
File
button at the bottom of the window. This
will take the user to the
Save/Read
window.
2. Press the Save Data button. Select Save Data, and enter a file name for the test.
Press Enter. The test and data are now saved. See
File Manager
section for
additional information.
3.8.10.7
Watt / Var / Va / Power Factor Applications
As previuously described, Watt and VAR transducers come in 1, 1 1/2, 2, 2 1/2 and 3
Element configurations. In the Transducer Setting Screen, the operator is required to
select what type of transducer is to be tested. Once selected, the internal firmware of the
MPRT unit will make certain assumptions and calculations based on the number of
elements selected. The following are detailed descriptions of the different elements and
the calculations required to calculate Watts and / or VARs.
3.8.10.7.1
Watt/VAR 1 Element
The single element watt transducer requires 1 voltage and 1 current to test. The MPRT
will automatically select the first voltage and current channels available,
V1
and
I1
. The
test will initially start at the default value voltage that is set in the
Default Setting Screen
.
For example, 120 Volts L-N. When the user inputs the
MAX.
Watts value in the
Transducer Setting Screen
, the firmware can calculate the required test current for full
scale value. Since the default angle will be 0
°
(zero degrees), the calculation is simple.
The formula required to calculate Watts is,
V1 * I1 * COS 0
°
= Watts
Example: The default voltage is 120.00 Volts AC, and the user inputs 500 Watts as Max.
Value. The current required for full scale output from the transducer is,
120 * I1 * COS 0
°
= 500 Watts simplifing,
I1 = 500/120, or I1 = 4.1667 Amperes
Therefore, when the user inputs 500 Watts in the
MAX
. value window, in the Test Screen
the test set should automatically show a test current value of 4.167 Amperes at an angle
of 0
°
. Note, the voltage is also in-phase with the current at 0
°
. Also, note that the current
is rounded up to 7 in the last digit displayed.
When the test is Started, the measured voltage and current outputs are displayed and the
calculated Watts is based on the measured voltage and current outputs. This is the value
that gets displayed in the
Transducer Test Screen
under the
MPRT Output
, next to the
Label of
Watt 1 Element
Another value of Watts gets calculated using the measured dc
Volts or dc milliampere output as displayed in the
Transducer Output
section. Let us
assume that in our example transducer, the output is in dc milliamperes. For this
example, let us say that 1 milliampere of dc current is equal to the full scale output of 500
Watts. Therefore, the theoretical output Watts from the transducer would be 500 Watts, if
the output current is 1 milliampere. For this example, let's say that the measured output
voltage is 120.01 Volts, at 0
°
, and the measured output current is 4.166, Amperes, at
0.0
°
. The measured output Watts would be,
120.01 * 4.166 * COS 0.0 = 499.96 Watts
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