Abstract: Good starting performance of AC-AC self-controlled synchronous machine is due to that at low rotor speed the machine commutation is completed by source voltage. In this case there is a commutation delay and the maximum operation time of the source voltage in the machine commutation is about half period of source voltage.The ability of machine commutation may be estimated by the commutation voltage-time area. At low rotor speed the. area is produced by the source voltage and machine electro motive force, and it is larger than the area at high rotor speed. So that the maximum machine torque at low rotor speed is larger than the maximum torque at high rotor speed also.In order to increase the ability of machine commutation at low rotor speed too new control methods for increasing the machine commutation vol-tagetime area. Are proposed in this paper. The principle of these methods is to decrease the firing angle a in the period of machine commutation. Using these new control methods the critical current of motor is more larger than the one controlled by ordinary method,so the overload ability of the machine using these new methods is increased also.As a result of the commutation delay reduction the rotor speed range of the machine operating at low speed can be expanded.The maximum machine torque is effected by the commutation angle Y of the machine. It should be regulated automatically when the rotor speed and load change. So that the maximum machine torque will be larger.