A motor-driven compressor includes an electric motor driven by a motor driver, which includes a switching element that converts DC voltage from a battery to AC voltage. A control unit controls the switching operation of the switching element. A temperature detector detects the temperature of the switching element. A voltage detector detects DC voltage applied to the switching element from the battery. The control unit suspends the switching operation of the switching element when the temperature detected by the temperature detector rises to a predetermined temperature threshold. The control unit also reduces counter electromotive force generated by the electric motor. The temperature threshold includes a first temperature threshold, corresponding to a withstand temperature of the switching element, and a second temperature threshold, which is higher than the first temperature threshold. The control unit switches the temperature threshold between the first and second temperature thresholds.

A vacuum pumping system includes a plurality of positive displacement vacuum pumps, and more particularly a plurality of positive displacement vacuum pumps working in parallel. The vacuum pumping system includes a management unit that carries out a synchronized control of all the positive displacement vacuum pumps of the vacuum pumping system and thus allows to check possible risk of contamination of the vacuum pumping system and carry out, if needed, the necessary corrective actions without requiring any modification to the construction of the vacuum pumping system.