Abstract: A speed control circuit arrangement for controlling a rotational speed of an AC commutator motor by an AC controlled rectifier element. The speed control circuit arrangement comprises a pulse transformer which is connected at the secondary winding to the control electrode of the AC controlled rectifier element and one of two main electrodes of the controlled rectifier element and supplies a trigger pulse to the control electrode, a variable resistor for adjusting the rotational speed of the motor, a first capacitor connected at one end through the variable resistor to the other main electrode and at the other end to one end of an AC power source, a pulse generating element connected across said first capacitor with the primary winding of the pulse transformer intervening therebetween, and a first resistor connected at one end to the one main electrode and at the other end to the other end of the AC power source through the first capacitor.