A pneumatic motor unit includes a housing with an air inlet passage, an exhaust air outlet passage, and a rotation motor which generates a pulsating exhaust air outlet flow. The motor unit further includes a voltage depending device which communicates signals in response to at least one of an actual motor condition and operation parameter values, and a voltage generating section which is connected to the voltage depending device and which includes a piezoelectric element provided in the exhaust air outlet passage and arranged to be activated by pressure pulses of the pulsating exhaust air outlet flow from the motor. The piezoelectric element is tongue shaped and rigidly secured at one end, and is arranged to be swung in a two-way movement relative to a central rest position to thereby generate an alternating current voltage.