Voltage Comparison
Below is a visual comparison between an ideally balanced network and the actual recorded voltages at the Modderbee municipal substation on September 5, 2023 at 03:40:00.
Navigating Power Imbalances
Understanding the impact of voltage asymmetry on three-phase motor systems
Voltage Comparison
Below is a visual comparison between an ideally balanced network and the actual recorded voltages at the Modderbee municipal substation on September 5, 2023 at 03:40:00.
Modderbee Balanced Phase-to-Neutral Voltages
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Modderbee Unbalanced Phase-to-Phase Voltages
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Click play to observe the rotation of both triangles. Consider the implications for a large three-phase electric motor operating under these conditions.
The green triangle represents an ideally balanced network, centered precisely at the origin (intersection of X and Y axes). The red triangle, however, shows the recorded voltages—noticeably off-center, indicating imbalance.
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Consequences of Voltage Imbalance
Unbalanced voltages in three-phase systems manifest as an off-center ellipse in vector diagrams. This distortion signals uneven magnetic forces within motor windings, leading to:
- Varying stress on motor bearings due to magnetic field fluctuations
- Increased vibration, reducing motor performance and lifespan
- Irregular torque output, causing mechanical stress and potential failure
- Risk of overheating and inefficiency during operation
The rotating dots in the video represent magnetic fields around the motor’s center. Vector values are intentionally reduced to enhance clarity and illustrate the magnetic dynamics more effectively.
Now imagine these stresses acting on a three-phase, 4-pole electric motor supplied by a 50Hz frequency, rotating at 1800 rpm. The mechanical and thermal implications are significant.
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Those who previously claimed that voltage imbalance at the Modderbee substation was “highly unlikely” may find this visual and technical evidence enlightening.
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