Our Technology

DDIS Technology

DDIS designs, manufactures and tests a new type of electric machine

Direct drive electrical can run as a motor or as a generator to produce energy without mechanical means (gearbox for example). The advantages of direct drive are many: simplicity, reliability, smaller footprint.

Axial Flux

The structure of conventional direct drive machines is of cylindrical type, a cylinder fitted with electrical windings (rotor) rotating in a fixed cylinder (stator) also equipped with coils in which electricity is produced. In this type of machine, the radial magnetic flux (magnetic flux oriented along the radius).

DDIS’s innovation is to use a structure with axial flow: a disc plate rotates in front another fixed disk (stator) . Also known as axial machine (the magnetic flux is parallel to the axis of rotation of the disk).

This innovative structure provides a higher compactness than the cylindrical structure and reduce the mass of the structure.

Permanent magnets

In a conventional machine, the magnetic field needed to produce electricity is generated by winding (copper wire on a metal core). These coils are bulky, complex manufacturing and energy consuming (they are always supplied to create a permanent magnetic field).

To overcome this difficulty, DDIS uses permanent magnets. These permanent magnets give the magnetic field without electrical power: thus, even in case of shortage of power supply, the magnetic flux is always present.

Multiphase machine

The electricity output of the machine is three phase, but it is produced by multiple sets of windings electrically connected together. It is as if the electrical machine consisted of several three-phase machines.

This feature limit the current flowing through each set of windings and therefore allows the use of components with lower power rating, even for a machine delivering high power. This also enables the machine to run at reduced power even in case of default on a coil.

Power Converter

DDIS technology is based on a permanent magnet synchronous machine associated with a full power electronic converter whose role is to provide high performance over the entire range of rotational speed.

This type converter AC / DC / AC IGBT is controlled by vector control using a PWM control. Its main functions are:

For the rectifier:

  • To control the power delivered perfectly and the operating point of the alternator according to its rotational speed to optimize performance
  • To adapt to the variable frequency alternator

For the inverter:

  • Adapt the power supplied to the fixed frequency of the grid on which the machine is connected
  • Control the power factor to not consume reactive power, and offer the same opportunity to provide reactive power for weak grids

For the chopper

  • Avoid to stop and restart the machine in case of short duration perturbations of the grid
  • Manage the breaking procedure in case of loss of the grid in order to avoid extreme mechanical stress

Moreover, it consists of multiple identical modules that enable special operation modes to optimize performance of electrical machine or in case of failure


The machine developed by DDIS has a modular structure consisting of a rotor and a stator equipped with windings called stator modules.

This principle of modularity allows to build a range of power with a reduced tooling. The number of stator modules increase with power, but this will remain the same.

Manufacturing Simplified

The axial internal structure and modularity facilitates manufacturing. The disks (stator and rotor) are flat parts easier to handle than large portions of cylinder in radial machines. And the various components (coils, magnets, stator sectors) can further be assembled using simple tools.

© 2009 Don Diego, (Rezé - France) for DDIS