process for preparing furan and phenanthrenes

摘要

The invention relates to a rotation-speed regulator for a motor, which is arranged in series with a switch, especially a triac, which is driven by a phase-gating control circuit. According to the invention, an additional load-limiting circuit is provided which acts on the phase-gating controller and by means of which, on reaching a maximum motor load which is dependent on rotation speed, limits the power supplied to the motor to a non-critical residual value Io. A restarting circuit is furthermore provided by means of which, after reaching this residual value, the rotation speed and the motor power are increased until the required rotation speed is reached.