Terms and quantities

01Phase RMS and peak current

RMS describes the effective current over a cycle; peak is its largest instantaneous magnitude. For a sinusoidal phase current, RMS = peak / √2. This relation does not apply unchanged to an arbitrary waveform. Always state both the quantity and convention. Try the current conversion helper.

02Phase, line and battery quantities

A phase quantity belongs to a winding phase. A line quantity is measured at the motor terminals; their relationship depends on the winding connection and waveform. Battery current is on the DC side of the inverter and is not interchangeable with motor-phase current. Preserve the phase or line label when comparing voltage or current.

03Mechanical and electrical angle

Mechanical angle describes rotor rotation. Electrical angle describes position within the repeating magnetic cycle: electrical angle = pole pairs × mechanical angle. A 12-pole machine has six pole pairs, so 60 mechanical degrees correspond to one 360-degree electrical cycle. State which angle your sampling uses.

04The d-axis and q-axis

These axes rotate with the rotor. The d-axis aligns with the rotor's magnetic reference; the q-axis is one quarter electrical cycle away. A current angle or a d-q current pair only has meaning with a defined axis, sign and current convention. Calibrate the rotor reference before interpreting loaded studies.

05Flux linkage and back-EMF

Flux linkage accounts for magnetic flux linking a winding, including its turns. Back-EMF depends on how that linkage changes with time and therefore on speed. A field solution at one angle can provide linkage at that angle; a waveform requires angular or time variation. Keep fundamental RMS distinct from total waveform RMS when comparing reported voltages.

06Cogging and loaded torque ripple

Cogging is position-dependent torque from the interaction of permanent magnets with the slotted magnetic structure without applied winding current. Loaded torque ripple is variation in torque under an applied-current condition. Neither amplitude can be inferred from a single position; state sampling, period and amplitude definition.

07Residual, convergence and uncertainty

A solver residual describes how well a discretised system satisfies its equations according to that solver's criterion. Mesh convergence asks whether the reported quantity stabilises as spatial resolution changes; angular convergence asks the same of position sampling. A small residual does not establish either convergence or a physical uncertainty bound.

On the evidence page, a model-to-reference percentage difference is a comparison of reported values. It is not the solver residual and is not an uncertainty interval. See how to read results.

08Temperature and temperature rise

Temperature is an absolute operating value, usually reported here in °C. Temperature rise is a difference relative to a specified ambient or coolant condition, reported in K or degrees of rise. A material-temperature input is an assumption; a thermal-model output is a prediction. Keep both distinct from a measured temperature.

09Verification and validation

Verification checks whether the numerical implementation solves the intended mathematical problem. Validation compares a model with physical observations under documented conditions. Agreement for a reference machine supports that particular comparison; it does not validate every geometry, operating condition or imported model. See the reference dossiers.