2. If two current channels that are to be used in parallel, set each to one-half of the output
requirement. The settings between three current channels will be one-third the output
requirement, and four channels would be one-fourth. Initiate all current channels
simultaneously by pressing the Start button. All parallel current outputs must be ON to
prevent internal shunting of current. Note: If only two currents are to be used, only
connect two currents in parallel, etc. for three or four channels. In other words do not
parallel a current channel if you do not intend to use it.
3. All current channels have amplitude control now operates simultaneously to provide the
desired test current. Selecting Ramp of the current Magnitudes will allow the user to ramp
all currents at the same time using the Control Knob. Total output is the sum of the
current shown on the individual current channel amplitude displays.
3.3.2 Currents in Series Operation
Two current channels may be connected in series in order to double the available compliance
voltage. High impedance electromechanical ground overcurrent relays have always been difficult
to test at high multiples of tap due to the winding impedance and saturation characteristics. The
peak voltage required can exceed the maximum output voltage of one MPRT current output
channel, depending on the required test current. By connecting two current outputs in series, the
compliance voltage is doubled, providing higher test currents through the load. To series the
current channels of the unit, perform the following:
Using the current channel test leads, connect the Red output terminals of current channel to the
relay under test. For “floating” ground units connect the two black return terminals together as
shown in the following figure.
Figure 23 Series of Two Current Channels
NOTE:
One current channel should be set to 0 degrees and the other current channel
should be set to a phase angle of 180 degrees so that the two compliance voltages add across
the load. DO NOT attempt to series more than two currents together.
The two current channels that are to be used in series set each to the same test current
magnitude. Initiate the two current channels simultaneously by pressing the Start button.
All current channels have amplitude control now operates simultaneously to provide the desired
test current. Selecting Ramp of the two current Magnitudes will allow the user to ramp the two
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