3-Level 100kHz PWM – High Tech

Triamec 3-Level PWM technology (lower graphics) using the example of a spindle rotating at 80'000 rpm compared to traditional servo drives (upper graphics)
Triamec 3-Level PWM technology (lower graphics) using the example of a spindle rotating at 80'000 rpm compared to traditional servo drives (upper graphics)
  • Reduction of Power Loss - Smoother Running

The 3-level technology, combined with 100kHz switching frequency, greatly reduces power dissipation in motors. This becomes clear when comparing the winding currents, provided by a conventional 16kHz drive, with those of the Triamec TSP700 3-level PWM servo drive. The adjacent graphs show a real 6kW­ milling spindle at 80'000 rpm. The low inductance of 1.2mH, typical for such motors, results in a very fast current rise with the high DC bus voltage of 500V here - a too low PWM frequency (upper graphs) leads to a large overshoot of the current (red curve) above the actually desired value (green curve).

 

With the TSP700, the voltage set by the PWM is approximated to the sine of the rotational frequency much more frequently and precisely. This results in a reduction of the ripple of the winding current by a factor of 10, which reduces the losses in the motor, the rotor rotates more smoothly and the leakage currents in the bearings are smaller.

  • Excellent control performance

Overall, the fast control cycle of 100kHz also improves current, speed and position control, which benefits not only spindles but all directly driven systems: Higher stiffness, better damping, more precise guiding behavior.

  • Economic advantages

Due to the high switching frequency, multi-pole versions can also be used for spindle motors. This allows higher torques to be achieved on the one hand and reduces costs on the other. Possible filter measures can be omitted or become significantly cheaper; the cooling effort is minimized.

For high cutting speeds, speeds of over 500'000 rpm can be achieved, with sinusoidal commutation for minimal losses in the motor.