This simulator models a generic variable-frequency drive — a six-diode rectifier, precharge resistor, DC-link capacitor bank, six-switch inverter and brake chopper — running a scalar V/f control law to accelerate a squirrel-cage induction motor across its speed range, including field-weakening operation above base frequency.
• 01 / Motor laboratory: a real-time 3D test bench (housing, stator, windings, rotor, shaft, bearings, fan, guard, six-terminal box, six-diode input rectifier bridge, precharge resistor and bypass, DC-link capacitor bank, six-switch inverter bridge, drive heatsink and cooling fan, brake chopper and resistor, gate-control PCB and DC-link measurement terminals) with home view, focus-selected-part, cutaway, exploded view, auto-rotate and expand/hide-labels controls, start, stop/coast, reset trip, apply locked rotor and release-shaft actions, run/pause toggle, 0.02 s and 0.2 s step buttons, and playback speed from 10x slow motion to 20x faster. • Settings: line-to-line supply (200-460 V), load torque, load law (constant vs quadratic fan/pump), combined inertia, frequency command (0-100 Hz), acceleration/deceleration ramp (2-50 Hz/s), low-frequency voltage boost (0-30 V), an illustrative PWM carrier frequency (1-10 kHz) and an enable-DC-brake-chopper checkbox. • 02 / Curves & measurements: an ideal PWM scope at the current operating point and a frequency-and-DC-link history chart, the underlying model equations, and live snapshot readouts of output frequency, rotor speed, fundamental line voltage, DC-link voltage, motor current and brake-resistor power. • 03 / Experiments: four guided scenarios (ramp to base speed at a 50 Hz command, low-speed 25 Hz fan duty, an 80 Hz above-base-frequency field-weakening run with a light fan load, and a fast-ramp comparison with high inertia showing electrical/mechanical lag), plus a Verification bench of automated model checks and a timestamped event log with a copyable trial report. • 04 / Learn & assess: four lessons (precharge limits capacitor charging, frequency and voltage work together, PWM is a switching pattern not a smooth voltage, regeneration raises DC-link energy), a two-question knowledge-check quiz, and a scope-and-references statement linking to a Microchip AC induction motor application note.
The DC link is modeled as an averaged energy store: EDC = ½·C·VDC² with C=4.7 mF, and dEDC/dt = Prectifier − Pinverter − Pbrake − Pbleed. On start, the precharge resistor limits the initial charging current into the capacitor bank; once charged, the model switches to a lower source resistance representing the closed precharge bypass. Because the input stage is a diode bridge, it can only deliver power to the DC link in one direction — it cannot return regenerated braking energy to the AC source, which is why a brake chopper and 75 Ω resistor exist to dissipate that energy above 620 V when the chopper is enabled.
The drive applies scalar V/f control to the same generic induction-motor equivalent circuit used across this lab set (Rs=0.65 Ω, R2′=0.45 Ω, Xs=X2′=1.1 Ω, Xm=28 Ω at 50 Hz on a star-equivalent base). Below base frequency, output voltage rises approximately proportional to frequency (with a configurable low-frequency boost added); once voltage reaches its ceiling near VLL,max ≈ VDC/√2, further frequency increases reduce magnetic flux and available torque — the field-weakening region you can reach directly in the above-base-frequency experiment. The frequency command ramps toward its target at the configured Hz/s rate, and the mechanical rotor follows with its own slip dynamics, so a fast electrical ramp with high inertia produces a growing gap between commanded frequency and actual rotor speed.
The ideal PWM scope shows a separately calculated common-mode-injected switching pattern at the current operating point — it illustrates what six-switch PWM synthesis looks like, but is not derived from the same fundamental-current solver driving the motor's torque and speed. The frequency-and-DC-link history chart lets you watch the DC-link voltage respond as the rectifier, inverter and any active brake-resistor power balance against each other, and shows frequency ramping toward the commanded value while rotor speed follows with slip.
Per the model's stated scope: this is an averaged diode-source/DC-capacitor energy model paired with a scalar V/f induction-motor model — switching losses, harmonics, dead time, EMC effects, full current-loop (vector) control and regenerative active-front-end operation are not simulated, and a diode front end cannot return DC power to the AC source in this or any comparable real topology. Iron loss, saturation, unbalance, bearing dynamics and subcycle switching transients are also outside the numerical model.
The DC-link capacitor bank (modeled at 4.7 mF) would draw a very high inrush current if connected directly to the rectified supply. The precharge resistor limits this initial charging current; once the link reaches its charged voltage, the model switches to a lower source resistance representing the closed precharge bypass.
No. The simulator uses a six-diode input rectifier, which is a one-way device — it cannot return regenerated DC energy to the AC source. Instead, the model includes a brake chopper and 75 Ω resistor that dissipate excess DC-link energy above 620 V when the chopper is enabled.
Below base frequency the drive raises voltage roughly in proportion to frequency (plus a configurable low-frequency boost). Once voltage reaches its ceiling near VDC/√2, further frequency increases reduce magnetic flux and available torque — this is the field-weakening region, which you can explore directly in the 80 Hz above-base-frequency experiment.
The PWM scope is an ideal, separately calculated common-mode-injected switching pattern at the current operating point, shown for illustration. It is not the same solver driving the motor's torque and speed, and the model does not simulate switching losses, harmonics or dead time.