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Synchronous Machine Parameters

This document discusses measuring the parameters of a synchronous machine through open circuit, short circuit, and DC resistance tests. The open circuit test varies the field current to measure the induced emf. The short circuit test varies field current to measure armature current. These tests are used to calculate the synchronous reactance by ignoring or including winding resistance. The measurements are not simultaneous so there can be errors from core saturation. Winding resistance inclusion has little effect on reactance accuracy.

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Shiza Shakeel
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67 views5 pages

Synchronous Machine Parameters

This document discusses measuring the parameters of a synchronous machine through open circuit, short circuit, and DC resistance tests. The open circuit test varies the field current to measure the induced emf. The short circuit test varies field current to measure armature current. These tests are used to calculate the synchronous reactance by ignoring or including winding resistance. The measurements are not simultaneous so there can be errors from core saturation. Winding resistance inclusion has little effect on reactance accuracy.

Uploaded by

Shiza Shakeel
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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Measurement of Synchronous Machine Parameters

Module 5-4

School of Science & Engineering


Covered So Far …
Circuit model of Synchronous Machine
Induced emf EA dependent on field
current IF
Synchronous Reactance as the
equivalent reactance seen at the
armature
Winding resistance as the lumped
resistance of the armature windings
Terminal voltage VT and frequency of
the system determined by the
standards governing operation of the
machine

School of Science & Engineering


Parameter Measurements
DC measurement of stator for Winding Resistance RA:
Conducted through dc resistance measurement of the synchronous machine
without any excitation
dc resistance is slightly smaller than the ac resistance due to skin effect but
gives a reasonable estimate
Open Circuit Test – EA vs IF
Voltage induced at the armature is measured by varying the field current
As no current flows in the armature, induced emf equals the terminal voltage
Linear for small IF but tapers off due to saturation at higher values of field
current
Short Circuit Test – IA vs IF
Armature winding is short circuited and the armature current is measured for
different values of IF
The net field does not cause the saturation of the core  relationship is linear
For the same value of IF, use EA and IA to calculate XS with or by
ignoring RA: RA2+XA2=(EA/IA)2
School of Science & Engineering
Accuracy and Other Considerations
Values of EA and IA are not measured simultaneously:
The measurement of EA is done through OCC and core may be
partially saturated for larger values of IF
The measurement of IA is done through SCC and core is
unsaturated
Approach accurate up to unsaturated values of XS
Winding resistance may be included or excluded in the
measurement of XS with little change in accuracy as the
error due to saturation is generally more significant
Short Circuit Ratio (SCR):
SCR = IF|Ea-rated at OC / IF|Ia-rated at SC where: EA is proportional to IF
 Ea-rated = k IF|Ea-rated at OC and Ia-rated = k IF|Ia-rated at SC/XS
 SCR = XS Ea-rated / Ia-rated  SCR = per unit value of XS

School of Science & Engineering


Next Topic
Synchronous Generator Operation
Alone
Conditions for parallel operation
Parallel operation
Operation in parallel with infinite bus (Grid)

School of Science & Engineering

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