DC machine (PM)

Permanent-magnet DC machine with armature resistance and inductance.

  • electrical
  • rotational
  • Modelica Standard Library
  • 3 ports
  • 6 parameters
BlockDC machine (PM)KinddcPmMachineLibraryMachines

Description

A DC machine whose field comes from permanent magnets. The armature is a resistance and inductance in series with an induced voltage proportional to speed; the torque is proportional to armature current. It runs as a motor or a generator, depending on the direction of power flow.

The machine constant is not entered directly. It is derived from the nominal operating point: the induced voltage at nominal current and speed is VaNominal − Ra · IaNominal.

Example

DC machines Permanent-magnet, shunt, and series DC machines on 100 V, with their shaft speeds.

100 V (PM)Ground (100 V (PM))100 V (shunt)Ground (100 V (shunt))100 V (series)Ground (100 V (series))PM machineSpeed (PM)Shunt machineSpeed (shunt)Series machineSpeed (series)Load 0.42 N·m·sFrame
In Gradara, select a DC machine (PM) block and press F1, then choose Open example. It opens as a new model in My models, ready to run.

Also in this example:DC voltageGroundFixed (rotational)Torsion damperSpeed sensor (ideal)DC machine (excited)DC machine (series)

Ports

Conserving terminals 3

  • a+pin_apelectrical

    Positive armature terminal. Current into pin_ap is the armature current ia; positive ia with positive speed is motoring.

  • a−pin_anelectrical

    Negative armature terminal.

  • shaftflangerotational

    Shaft, rotational. The rotor inertia Jr sits on this flange. The stator is fixed to ground internally.

Parameters

  • Nominal voltageVaNominal100 V

    ≥ 0

    Armature voltage at the nominal operating point, in volts. Must exceed Ra · IaNominal.

  • Nominal currentIaNominal100 A

    ≥ 0

    Armature current at the nominal operating point, in amperes.

  • Nominal speedwNominal149.2 rad/s

    ≥ 0

    Speed at the nominal operating point, in rad/s. The default 149.2 rad/s is 1425 rpm.

  • Armature resistanceRa0.05 Ω

    ≥ 0

    Armature resistance, in ohms.

  • Armature inductanceLa0.0015 H

    ≥ 0

    Armature inductance, in henries. Sets the electrical time constant La/Ra.

  • Rotor inertiaJr0.15 kg·m²

    ≥ 0

    Rotor moment of inertia, in kg·m².

Equations

Modelica
kΦ = (VaNominal − Ra · IaNominal) / wNominal
pin_ap.v − pin_an.v = Ra · ia + La · dia/dt + kΦ · ω
τe = kΦ · ia
Jr · dω/dt = τe + flange.τ

Implementation

Modelica Standard Library 4.1.0Modelica.Electrical.Machines.BasicMachines.DCMachines.DC_PermanentMagnet
MSL documentation

Assumptions and limitations

  • Constant magnet flux: no armature reaction, saturation, or demagnetization.
  • No friction, core, stray-load, or brush losses (the library loss records are left at zero).
  • Temperatures are fixed at 20 °C, so Ra does not change with heating.

Tips

  • To match a datasheet, enter the rated voltage, current, and speed; the torque constant follows. With the defaults kΦ ≈ 0.637 V·s/rad (N·m/A).
  • Drive it from an H-bridge or a DC source; connect a load with Inertia or Shaft load.

Used in

These larger examples use it too. Open them from Examples in the app.

  • EV drivetrain

See also

Select a block in Gradara and press F1 to open its page offline.