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UMG 96-PA
/
UMG 96-PA
MID
45
13.5.1 Principles of the pointer diagram
The pointer diagram provides a graphic
description of the phase shift or the phase angle
between voltage and current. The pointers rotate
with a consistent angle speed - proportionate to
the frequency of voltage and current - around an
original source. Thus, the pointer diagram shows
the current state of the variables in an AC circuit.
Illustration of ohmic resistance:
·Voltage and current are in phase
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u
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u
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Illustration of inductance:
·The voltage leads the current
·For an ideal coil, the phase shift is 90°
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u
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u
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Illustration of capacitance:
·The current leads the voltage
·For an ideal capacitor, the phase shift is 90°
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In a combination of the states, the phase angle
“current to voltage” can assume values of
between -90° and +90°.
U
I
Current:
Illustrated wFth short
poFnters
Voltaie:
Illustrated wFth loni
poFnters
Example pointer diagram (3 phases)
UL1
IL1
IL2
UL2
UL2
IL3
Current and voltage are out of phase. The current
leads the voltage, causing a capacitive load to
the line.
