148 8 Industri I d d s ia l l Rob o bo tics i s Fu un ddamentals Copyright Goodheart-Willcox Co., Inc. Copyright Goodheart-Willcox Co., Inc. Activity 6 -4 AC Synchronous Motors Objectives The ac synchronous motor used in robotic systems is commonly classified as a fi constant-speed device. It has extremely rapid starting, stopping, and reversing abilities. Motors of this type require only a simple clockwise-stop-counter- clockwise rotary switch for control. The starting and running currents of a synchronous motor are identical, which is unique for ac motors. This characteristic means that a motor of this type can withstand a high inrush of current when direction changes occur. As a general rule, the synchronous motor can even be stalled without damaging the motor. Motors of this type are commonly used as drive mechanisms for robotic sys- tems in machinery operations. Starting begins within 1 1/2 cycles of the line fre- quency, and stopping occurs in fi ve mechanical degrees of rotation. This motor fi represents a unique part of all servomechanisms used in precision rotary control applications today. In this activity, a simple test circuit will be constructed so you may observe starting and stopping of an ac synchronous motor and the current fl ow characteristics of the motor. fl Equipment and Materials • AC synchronous motor—Superior Electric Type SS150 or equivalent motor rated at no more than 200 in/oz. • Capacitor—3.75 μF, 330V ac. • Resistor—250 Ω, 25 W. • SPST switches (3). • Isolated ac power source—120V. • AC ammeter—0–5 A. • Piece of wood. Safety Use protective eyewear during this activity.