Every input explained.
Every symbol defined.

Target full torque [Nm]

The maximum positive driving torque that should remain available at the target full-torque speed.

Default input: 10 Nm. The model deliberately caps available torque at this target; it does not show the absolute physical maximum of the motor.

Target self-rotation speed [rpm]

The speed the wheel should reach under FFB torque, for example during self-alignment or countersteer in drifting. Default input: 300 rpm.

This is a loaded operating requirement, not a no-load speed. The specified minimum self-rotation torque must still be available at this speed.

Target full-torque speed [rpm]

The speed at which the full target torque should still be available. I use 10 Nm at 200 rpm, because I regard 200 rpm as the maximum wheel speed I can physically reach during rapid hand movements.

This is an input target for the torque–speed characteristic. It is distinct from the calculated full-torque corner speed, which depends on supply voltage, motor parameters and current limits.

Minimum torque at target self-rotation speed [Nm]

The minimum positive driving torque required at the target self-rotation speed. I use 2 Nm at 300 rpm: this provides a small margin above the torque needed to turn my wheel with its attached button box and no additional load.

The required torque depends on wheel inertia, friction and desired acceleration. The calculator does not solve the wheel acceleration dynamics.

Torque constant Kt [Nm/A]

Kt relates torque to torque-producing current:

The default input of 0.56 Nm/A was experimentally determined for the project motor. It refers to the current-amplitude convention used by the model. Do not use an RMS-based constant without converting its current convention.

Torque was measured with a digital torque wrench in Peak mode. Two phase currents were read from the MKS XDrive Mini through ST-Link, and the third was inferred from Kirchhoff’s current law. A peak torque measurement does not establish a continuous torque rating.

Line-to-line resistance [Ω]

Disconnect the motor from the controller. Measure each of the three wire pairs with the motor stationary and at a known temperature. Results should be similar. Significant differences can indicate a damaged motor, but first rule out measurement error, poor contacts or faulty connections.

The project used a four-wire measurement at 1 A to reduce the effect of leads and contacts. Default input: 0.35 Ω.

For a symmetrical star-connected motor, line-to-line resistance is twice one phase winding’s resistance. The model formulas already include this conversion: enter the measurement without dividing it by two. Other winding connections or current conventions require the model to be checked.

Winding temperature rise [°C]

Default input: 50°C. The project assumes a resistance measurement at 25°C and an intended maximum magnet operating temperature of 75°C. The difference, 75 − 25 = 50°C, is used as the temperature-rise assumption.

The calculator applies that rise to winding resistance:

For 0.35 Ω and a 50°C rise, the calculated resistance is 0.418775 Ω.

The 75°C limit is the project owner’s assumption, not a universal magnet rating. Winding and magnet temperatures can differ. This correction does not predict either temperature, establish a safe duty cycle or verify magnet temperature.

Current at 100% Power Limit [A]

The controller current represented by 100% FFBeast Power Limit in your hardware and firmware configuration.

The project uses 37 A with Amplifier Sense Gain 80 V/V. If a different gain is used, enter the corresponding current scale. Verify the scaling for your controller.

This value is the denominator in Required Power Limit and caps the modeled current. It is not a calculated operating current or a continuous thermal rating.

PWM voltage utilization [%]

This factor converts selected DC supply voltage to the voltage budget used by the loaded SVPWM model:

For example, 85% utilization with a 36 V supply gives a calculated budget of 30.6 V. This is voltage utilization, not controller energy efficiency or a commanded fixed PWM duty cycle.

Power-stage efficiency [%]

Default input: 95%. Motor electrical input, approximated as mechanical output plus copper losses, is divided by this efficiency to estimate power-stage input. This is a design assumption, not an efficiency measurement at every operating point.

Minimum required supply voltage [V]

The calculated minimum DC voltage required to satisfy both specified torque–speed conditions.

Both required voltages combine back-EMF, which rises with speed, and the resistive winding drop, which depends on torque-producing current and resistance. The larger requirement is divided by voltage utilization to give the required DC supply voltage. More detail is available in the selection algorithm.

Selected supply voltage [V]

The supply voltage you choose to evaluate. Enter a value or select 12, 24 or 36 V. This is an input; the minimum required voltage is a separate calculated result shown beside the selector and in the headline.

You can select less than the calculated minimum to compare performance. Hardware voltage ratings and regenerative energy handling require separate verification.

Stall torque — stationary wheel [Nm]

The calculated torque with the wheel stationary, at 0 rpm. It is limited by target full torque, controller current and voltage available across winding resistance.

This is torque capability at standstill, not a continuous holding torque rating.

Torque at target full-torque speed [Nm]

The torque available at the speed entered in Target full-torque speed. With 200 rpm entered, this result shows the available torque at 200 rpm.

Compare the result with Target full torque. A lower result means the selected supply cannot provide the requested torque at that speed.

Torque at target self-rotation speed [Nm]

The positive driving torque available at Target self-rotation speed. Compare it with Minimum torque at target self-rotation speed.

The project requirement is:

This is torque at the specified speed, not a calculated speed.

Full-torque corner speed [rpm]

The calculated speed above which voltage limiting reduces available torque below the torque available with the wheel stationary.

This boundary changes with supply voltage and motor parameters. It can be above or below the input target full-torque speed.

Self-rotation speed at minimum torque [rpm]

The maximum calculated speed at which the wheel can still provide the specified minimum torque. For a 2 Nm minimum, it is the speed available while retaining at least 2 Nm.

If that torque is unavailable even with the wheel stationary, the result is marked Not achievable. If the minimum torque is set to zero, the result is the zero-torque speed boundary of the loaded SVPWM model. The status still checks whether the requested self-rotation speed is reachable; this is distinct from the separate six-step no-load estimate.

No-load speed — six-step estimate [rpm]

The idealized rotational speed without external shaft load, calculated separately for overmodulation/six-step:

This is not taken from the loaded SVPWM torque curve. It does not imply that loaded torque remains available at that speed.

Temperature-adjusted resistance [Ω]

The measured resistance corrected for the specified temperature rise:

This value is used for resistive voltage drop and copper losses. It is a calculation result, not another measurement input.

Available voltage budget [V]

The selected DC supply voltage multiplied by the voltage utilization fraction:

For 36 V and 85% utilization, the calculated budget is 30.6 V. This quantity is compared internally against back-EMF plus winding voltage drop. It is not a specified phase RMS voltage or an energy-efficiency-adjusted supply voltage.

Total required supply power [W]

Calculated DC supply power at the selected achievable operating point, before adding a design margin:

This includes mechanical output, copper losses, assumed controller power-stage losses and fixed electronics draw. It is not a supply nameplate rating or the global maximum over all speeds.

Recommended supply power / Supply power + 20% [W]

The headline recommended power and the row with a 20% margin show the same result:

The margin applies to all DC power, including electronics. In the 10 Nm, 200 rpm, 36 V example:

A lower calculated power with insufficient voltage does not mean the performance requirements have been met.

Supply current draw [A]

Calculated current drawn from the selected DC supply:

This is DC input current, not motor phase current or Iq. The 36 V example gives 9.19 A.

Supply current + 20% [A]

Current including the same design margin:

The 36 V example gives 11.03 A. Changing the selected voltage changes the current required for a given power.

Operating point [Nm / rpm]

The torque and speed used together for the power calculation:

This selects an achievable point in the model; it does not search the full speed range for maximum power.

Torque-producing current [A]

The current used to calculate losses after applying target, controller and standstill voltage limits:

It corresponds to the available stationary-wheel torque and may be lower than the requested target current.

Mechanical power [W]

Mechanical output at the selected operating point:

At standstill, mechanical power is zero even when the motor produces a substantial holding torque.

Copper losses [W]

Resistive losses in all three windings:

The coefficient follows the current-amplitude and measured line-to-line resistance conventions for the symmetrical star-connected motor. Losses increase with the square of current.

Power-stage losses [W]

Estimated controller power-stage losses:

Fixed electronics draw is added separately. Constant efficiency is an assumption and does not reproduce every real operating point.

Electronics power draw [W]

The fixed power used by controller electronics and the auxiliary supply. This is the value entered in Electronics power draw. It is added to motor power and controller power-stage losses:

Pelectronics is added separately, after power-stage efficiency is applied to motor input power. It is also included at standstill. The project input is 5 W.

Power draw at standstill [W]

Estimated DC draw at the same modeled holding current, with the wheel stationary:

Mechanical power is zero, but winding losses, controller losses and electronics consumption remain. This detail result does not include an extra 20% margin.

Required Power Limit [%]

This result converts target full torque into the FFBeast current-limit setting using measured Kt and the configured current at 100% Power Limit:

For Ttarget = 10 Nm, Kt = 0.56 Nm/A and Icontroller,max = 37 A, required current is 17.86 A and the setting is 48.26%. These are calculated example results, not default inputs.

A value above 100% means the requested torque exceeds the configured controller current limit. Voltage must also be sufficient at the required speed. Power Limit is not a percentage of the supply rated current or a thermal safety rating.

Torque vs. speed

The horizontal axis is wheel speed [rpm]; the vertical axis is available positive driving torque [Nm]. The green line stays flat while full target torque can be maintained. When voltage is insufficient to retain that torque at increasing speed, torque falls.

If current or voltage already limits torque with the wheel stationary, the flat portion starts below the requested target. The amber horizontal line marks minimum self-rotation torque.

Required supply voltage vs. torque

The horizontal axis is torque [Nm]; the vertical axis is required DC supply voltage [V]. Each curve is the voltage requirement at 0 rpm, the target full-torque speed or the target self-rotation speed:

This is the supply voltage required for one operating point on a curve; the headline minimum checks the larger of both project requirements. The horizontal amber line is selected DC supply voltage.

Solid diamond markers show the two required project points: target full torque at the target full-torque speed, and minimum torque at the target self-rotation speed. The cards below the chart show their torque, speed and required supply voltage. The larger required voltage determines the headline minimum supply voltage. Hollow circular markers, their callouts and vertical guides show the available torque at both input speeds, including target torque and controller current caps. If voltage limits positive torque, a point meets the supply line. If another cap applies first, it lies below the line. If back-EMF already exceeds the budget, torque is clipped to zero and the required-voltage callout can be above the supply line: that point is not feasible.

Green and blue rectangles use opposite diagonal hatching so that both remain distinguishable when their bounds coincide. They are visual bounds below selected voltage and left of the available-torque guides, not complete feasible regions. A feasible point must also be on or above its speed curve and respect current and torque caps. The supply is assessed at its horizontal voltage line. Stall below the chart means the capped torque at a stationary wheel.

Torque vs. FFBeast Power Limit

The horizontal axis is controller current setting [%]; the vertical axis is theoretical torque [Nm]:

This chart does not apply voltage or speed restrictions. The target-torque line intersects the theoretical characteristic at Required Power Limit. Above 100%, that intersection is outside the shown controller range and a message replaces the marker. The linear characteristic omits magnetic saturation and temperature limits.