Simulate the steady-state three-phase currents and terminal voltage of a PMSM driven by a space-vector PWM inverter. Enter your motor parameters and RMS back-EMF, set an operating point, and view the settled waveforms.
RMS mode assumes a sinusoidal back-EMF; the PM flux linkage is
ψm = √2 · Erms / ωe,
with ωe = 2π·(RPM/60)·(poles/2).
Custom CSV mode imports a measured/FEA back-EMF (angle, Ea, Eb, Ec
over one electrical period). Its amplitude is scaled by RPM / captured RPM,
the fundamental is auto-aligned to the q-axis, and the harmonics carry through as
ed(θ), eq(θ) — so the current picks up the
resulting distortion.
Either way, currents are integrated in the rotor (d-q) frame so saliency
(Ld ≠ Lq) is exact, then run to steady state before plotting.
This free PWM waveform calculator simulates the three-phase current and terminal-voltage waveforms a PMSM produces when driven by a Space-Vector PWM (SVPWM) inverter. Enter the motor's electrical parameters, DC-bus voltage, switching frequency and back-EMF, and the tool time-steps the drive to show the steady-state phase currents, voltages, RMS values, modulation index and harmonic distortion — a fast way to see how an inverter and motor behave together before you touch hardware.
A three-phase voltage-source inverter can only switch each output between the positive and negative DC rail. Pulse-Width Modulation (PWM) rapidly chops between these two levels so that, averaged over a switching period, the output tracks a desired sinusoidal reference. Raising the switching frequency makes the averaged voltage smoother and the current ripple smaller, at the cost of higher switching losses in the transistors.
SVPWM treats the three phase voltages as a single rotating space vector and synthesises it from the inverter's eight possible switching states (six active vectors plus two zero vectors). By spending calculated dwell times on the two active vectors that bracket the target and sharing the remainder between the zero states, SVPWM produces a rotating voltage with markedly cleaner harmonics than simple sine–triangle PWM. Its biggest practical advantage is about 15% more usable fundamental voltage from the same DC bus, because it naturally adds a common-mode third-harmonic component that improves DC-bus utilisation.
The modulation index m measures how much of the available DC-bus voltage the reference demands. In the linear region SVPWM reproduces the reference faithfully; push m too high and the inverter enters overmodulation, where the output flat-tops, the fundamental sees diminishing returns and low-order harmonics appear. This calculator reports the modulation index and flags when a design is heading into saturation, so you can size the DC-bus voltage correctly for the required speed and current.
The interaction of the PWM voltage with the motor inductance sets the current ripple. A higher switching frequency or a larger motor inductance smooths the current; a low switching frequency leaves visible ripple riding on the fundamental. The tool quantifies waveform quality with Total Harmonic Distortion (THD) for the current, letting you trade switching frequency — and therefore inverter losses — against current smoothness.
The current that actually flows is governed by the difference between the applied PWM voltage and the motor's back-EMF, acting across the winding resistance and inductance. That is why this simulator takes the back-EMF (either as an RMS value or a measured/exported waveform) as an input: a distorted back-EMF shows up as distortion in the current — exactly what you want to catch early when pairing a motor with its drive.
Both aim to synthesise a sinusoidal output, but SVPWM works in the vector domain and effectively injects a third-harmonic common-mode term. The result is lower harmonic distortion and roughly 15% more fundamental voltage from the same DC bus, which is why most modern motor drives use it.
It shows how close the drive is to its voltage ceiling. Staying inside the linear region keeps the current clean; exceeding it (overmodulation) adds low-order harmonics and torque ripple, and usually means the DC bus is too low for the demanded operating point.
A higher switching frequency reduces current ripple and audible noise and improves control bandwidth, but it raises transistor switching losses and heat. The right choice balances waveform quality against inverter efficiency.
To take a validated motor design all the way to a full machine model, the MotorDesignSoftware desktop suite automates FEMM geometry, meshing and post-processing for back-EMF, cogging, torque-ripple, loss and NVH analysis.