Altistart 48 Enclosed Altistart 48 Soft Starters Page 38 Conventional Starting Curves

38 Altistart 48 soft starters for asynchronous motors Conventional Starting Curves Conventional starting curves The following graphs illustrate the starting curves of commonly used starting methods for starting a motor. Direct starting Starting current: 4 to 8 times the nominal current Starting torque: 0.5 to 1.5 times the nominal torque Characteristics: - Motor with 3 terminals, low and medium power - On-load starting - High current peak and voltage drop - Simple device - Sudden starting for the mechanism No parameter adjustment (1) Load torque Wye delta starting - Motor with 6 terminals - No-load or low resistive torque starting - High current peaks and torque when changing to Wye Delta mode - A device requiring maintenance - Subject to mechanical stress when starting No parameter adjustment (1) Load torque (2) Direct Starting Primary resistor starting Starting current: 4.5 times the nominal current Starting torque: 0.5 to 0.75 times the nominal torque Characteristics: - Motor with 3 terminals, high power - Starting with increasing resistive torque - High current peak - A large, bulky device requiring maintenance - Subject to mechanical stress when starting No parameter adjustment (1) Load torque (2) Direct Starting Autotransformer starting Starting current: 1.7 to 4 times the nominal current Starting torque: 0.4 to 0.85 times the nominal torque Characteristics: - Motor with 3 terminals, high power - Large voltage drop and current peak when connected at full voltage - A complex, bulky device requiring maintenance - Subject to mechanical stress when starting No parameter adjustment (1) Load torque (2) Direct Starting 6 5 4 3 2 1 0 0 0.25 0.5 0.75 1 Motor speed I/In 2.5 2 3 1.5 1 0.5 0 0 0.25 0.5 0.75 1 Motor speed T/Tn (1) 6 5 4 3 2 1 0 0 0.25 0.5 0.75 1 Motor speed I/In (2) 2.5 2 3 1.5 1 0.5 0 0 0.25 0.5 0.75 1 Motor speed T/Tn (1) (2) 6 5 4 3 2 1 0 0 0.25 0.5 0.75 1 Motor speed I/In (2) 2.5 3 2 1.5 1 0.5 0 0 0.25 0.5 0.75 1 T/Tn (1) (2) Motor speed 6 5 4 3 2 1 0 0 0.25 0.5 0.75 1 Motor speed I/In (2) 2.5 2 3 1.5 1 0.5 0 0 0.25 0.5 0.75 1 Motor speed T/Tn (1) (2) Starting current Starting torque

Previous Page
Next Page