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RPFM Modulator

Recursive Pulse Frequency Modulator

The RPFM is a space vector modulator so it can operates in the whole sinusoidal linear region and extends to space vector region.

Additionally the RPM modulator can operates out of linear zone with partial saturation or full saturation (six-steps mode).

The main characteristics of RPFM 2 levels modulator are:

  • output changes at fixed time (time unit). This guarantee a minimum ON/OFF command pulse to power stage.
  • usage of all 8 vectors or just 7 vectors. In 8 vectors mode the switches counts are minimized
  • no more than one output phase changes per time unit.
  • evaluation of DC_LINK voltage at fixed time.

The  RPFM 3 levels modulator is extension of 2-levels with test following characteristics:

  • generation of 27 vectors,
  • the required power stage is T-type NPC topology.

The switch from 2 to 3 levels mode (and vice versa) can be controlled on the fly according required working condition
In both 2 and 3 levels modes, the change of time unit (also minimum pulse width) can be executed on the fly according required working condition.

Sinusoidal reference  The sinusoidal modulator can transfer DC_LINK / 2 voltage to motor.

Assuming this value is 100%, the space vector extends to 115.47% = 2 / sqrt(3)

and saturated sine wave extends to 127.324% = 4 / π

Space Vector reference The space vector modulator can transfer 2 / 3 * DC_LINK volts to motor

Assuming the space vector as 100% reference, the sine wave is lower than 86.603% = sqrt(3) / 2

and saturated sine wave extends to 110.266% = 2 * sqrt(3) /π