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Unfortunately not all motor suppliers use the same parameters in the data sheets. Therefore the Servo Motor Editor uses the most common parameters as described in this section. All parameters are defined using a motor temperature and ambient temperature of 25° C.

General Data

This general section contains the unique identifier of the motor (Keyname) and some additional data, which can be filled in freely.



The name of the motor



Additional Info



A unique name (no duplicates allowed in the motor list) to identify the motor.



The motor type:

1.AC Synchronous
2.Brush DC Iron
3.Brush DC moving coil
4.Brush DC Disc Rotor
5.AC Synchronous Linear
6.Brushless DC

In the Editor, you can select from a drop down list. In the data file (see next section, the corresponding numbers are used).



Date at which the motor info was entered



The price of the motor


Delivery Time

Delivery Time



The name of the data file that is used

Nominal Data

Many data sheets describe the nominal operating point of a motor. The nominal operation point is characterized by a fixed current that is supplied to a motor with an initial temperature of 25º C that will result in a heating up of the coils to the exactly the maximum temperature. Because a current alone is not enough to describe the state of a motor, the operating point is always given at a certain speed. Although the other parameters (torque and power) can be derived from the current and speed they are usually printed in most data sheets.


Torque [N.m]or Force[N]

Torque or force at nominal operation.


Current [A] or [Arms]

Current at nominal operation.


Speed [rpm]or [m/s]

Speed at nominal operation.


Voltage [V] or [Vrms]

Voltage at nominal operation.


Power [W]

The output power at nominal operation.


Life [hour]

Expected Lifetime of the motor under normal operation.


As described, the definition of current and voltage depends on the selected motor:






1. AC Synchronous

rms phase current (A)

rms phase to phase voltage (V)


2. Brush DC Iron

current (A)

voltage (V)


3. Brush DC moving coil

current (A)

voltage (V)


4. Brush DC Disc Rotor

current (A)

voltage (V)


5. AC Synchronous Linear

rms phase current (A)

rms phase to phase voltage (V)


6. Brushless DC

peak current (A)

peak phase to phase voltage (V)

Max/Peak Values

The maximum parameters indicate the maximum performance of the motor and are used to show the limits in the torque speed plot as explained in chapter 3. The parameters do not indicate an operating point on the torque speed curve. The maximum parameters are preferably measured at a temperature of 25º C.


Torque [N.m]or Force[N]

The maximum short-time or torque or force (also known as stall torque).


Current [A] or [Arms]

The maximum short-time current.


Speed [rpm]or [m/s]

The maximum speed.


Voltage [V] or [Vrms]

Maximum short-time voltage.


Power [W]

The maximum short time power.


The currents and voltages are defined the same as for the nominal parameters.

Electrical Data


R [ohm]

The resistance at 25° C.


L [H]

The terminal inductance.


alpha_c [1/degC]

The temperature dependency of the coil resistance.


ktc [1/degC ]

The temperature dependency of the magnets.


poles [-] or pitch[m]

The number of poles (always an even number) or pole pitch (distance N-N poles).


As described, the definition of resistance and inductance depends on the selected motor:






1. AC Synchronous

phase to phase resistance (ohm)

phase to phase inductance (H)


2. Brush DC Iron

resistance (ohm)

inductance (H)


3. Brush DC moving coil

resistance (ohm)

inductance (H)


4. Brush DC Disc Rotor

resistance (ohm)

inductance (H)


5. AC Synchronous Linear

phase to phase resistance (ohm)

phase to phase inductance (H)


6. Brushless DC

phase to phase resistance (ohm)

phase to phase inductance (H)

Mechanical Data

The mechanical data describes the motor inertia and losses.


J_rotor [kg.m2] or m_motor [kg]

The rotor inertia or the the moving mass of the motor.


d [N.m.s/rad]or [N.s/m]

Mechanical damping and eddy current losses.


T_fric [N.m] or [N]

Mechanical friction and hysteresis losses.


T_cog [N.m] or [N]

The amplitude of the cogging torque.

Thermal Data

The thermal data is used for the thermal model as explained in chapter 4. Zero values for the thermal resistances are replace by a small value (1e-2) to prevent division by zero.


Temp_amb [degC]

The ambient temperature.


Temp_initial [degC]

The initial temperature of the coils and housing.


Temp_max [degC]

The maximum coil temperature.


RT1 [degC/W]

The thermal resistance between rotor and stator.


RT2 [degC/W]

The thermal resistance between stator and environment.


CT1 [J/degC]

Thermal capacity of the rotor.


CT2 [J/degC]

Thermal capacity of the stator.

Physical Data

This section describes the motor dimensions and maximal load.


F_axial [N]

The maximum axial force applied to the motor shaft.


F_radial [N]

The maximum radial force applied to the motor shaft.


m [kg]

The motor weight.


D_motor [m]

The motor diameter.


L_motor [m]

The motor length.


D_shaft [m]

The shaft diameter.


L_shaft [m]

The shaft length.

Derived Data

These are values that can be found in many data sheets. They are useful for selection criteria when searching for motors.


K_nom [N.m/A], [N.m/Arms] or [N/Arms]

The torque constant or force constant at 25° C and nominal currents.


K_max [N.m/A], [N.m/Arms] or [N/Arms]

The torque constant or force constant at 25° C and at peak currents.


S [N.m.s/rad] or [N.s/m]

The steepness.


tau_m [s]

The mechanical time constant (J_rotor/S or m_motor/S).


P_dis [W]

The maximal continuous dissipation.


tau_T1 [s]

The thermal time constant of the rotor (RT1* CT1).


tau_T2 [s]

The thermal time constant of the stator (RT2* CT2).

Additional Data


20-sim model []

Not implemented yet.