This regulator has been made specially for normal asynchronous three-phase squirrel cage motors with star connection, connected to fans or aspirators, whose absorption is lower than 6-10-16A, depending on the model, and for nominal star phase-neutral voltage up to 220V (380V on line ±10%). It allows speed regulation from about 30 up to 100% of nominal speed by choking the supply voltage with triac circuits. The use of this system may cause small motor overtemperature on low R.P.M. This anomaly, however, is acceptable if we consider the regulator to be particulary reliable, small and cheap. The regulator can be used with any ohmic load and within its electric features. For this use it is possible to supply regulators without minimum adjustment, therefore adjustment field varies from 0 up to 100% of grid voltage. It is housed in a IP55 plastic container: controls and adjustments are situated on the front panel.