Voltage-magnitude errors and phase-displacement errors create negative-sequence voltage. At a motor terminal, that component produces a reverse-rotating air-gap field, elevated rotor loss, torque pulsation and accelerated thermal ageing. Agulhas Utilities Corporation makes this hidden stressor measurable, traceable and manageable.
Three-phase voltage can be unequal in magnitude, displaced from its intended 120° phase separation, or both. The physically relevant quantity for rotating machinery is the negative-sequence component, V₂, rather than a magnitude-only proxy.
Positive sequence produces the intended forward-rotating field. Negative sequence produces an opposing field. In a running induction motor, the rotor sees this reverse field at a relative slip of approximately 2 − s; near normal operating speed, that means rotor current at nearly twice supply frequency.
We resolve measured three-phase voltage and current into positive-, negative- and zero-sequence components. The outcome is a defensible record of the electrical stressor acting on motors, generators, transformers and associated plant.
We investigate phase loading, feeder and connection integrity, supply impedance, transformer configuration, single-phase demand, switching events and abnormal operating conditions to identify the origin and transfer path of unbalance.
We review negative-sequence current protection, thermal duty, alarm and trip thresholds, and coordination with overload, stall, phase-loss and upstream functions—matched to the actual machine and process duty.
Adjust magnitude and displacement-angle errors. The live phasor plot and waveform display separate the supply into forward positive sequence, reverse negative sequence and zero sequence. Use this during a client briefing, training session or technical presentation.
Blue: positive sequence, forward rotation. Amber: negative sequence, reverse rotation. Red, blue and green: actual phase-voltage phasors. This explanatory voltage model does not calculate machine-specific current; that requires the motor’s sequence impedances, slip and load.
The negative-sequence field counter-rotates relative to the intended air-gap field. It reduces available accelerating torque, adds a pulsating torque component and creates additional rotor and stator loss. The resulting vibration, heating and torque stress can be misdiagnosed as purely mechanical defects.
Engage Agulhas for sequence-component analysis, disturbance monitoring, unbalance source tracing, motor-risk assessment and ANSI 46 protection coordination for critical rotating plant.
Engineering note: Site-specific recommendations require measured electrical and operating data, confirmed equipment ratings and protection documentation.