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1、Motor Start Theory,电机起动原理,T-2005-11001MST,Low Slip v Full Slip 低滑移与满滑移,0,50,100,150,200,250,300,100,90,80,70,60,50,40,30,20,10,0,SLIP (%),FULL LOAD TORQUE (%),0,100,200,300,400,500,600,700,CURRENT (%),A motors start performance characteristics set the limits of what can be achieved with either a ful
2、l voltage or reduced voltage starter. 电机起动性能规定使用全电压起动器或降压起动器能达到的极限值。 It is especially important to consider motor start characteristics when seeking to: - Minimise start current Maximise start torque 当尝试以下方式时考虑电机起动特性尤其重要： - 将起动电流降至最小 - 将起动扭矩增至最大,Motor Performance 电机性能,Rotor design affects starting p
3、erformance. 转子的设计影响起动性能。 Stator design affects full speed performance. 定子的设计影响全速性能。 The shape, position and material of the rotor bars affect the current drawn and torque produced during motor starting. 转子杆的形状、位置和材料影响引入电流和电机起动时产生的扭矩。,Motor Performance 电机性能,A motors start performance can be identifie
4、d by examining the motor data sheet. 电机起动性能可通过检查电机数据表得到确认。 The table details selected performance data for a range of 110kW motors. 数据表详述了110kW电机系列选用的性能数据。,Typical Motor Data 典型电机数据,Motor Speed FLC LRC LRT % FL Torque (rpm) (amps) (%FLC) (%FLT) Efncy 3xFLC A 1470 191 600 263 93 65.8 B 1475 184 600 1
5、90 93.5 47.5 C 1475 191 570 150 92 41.6 D 1480 187 660 190 94.5 39.2 E 1470 185 550 120 92 36 F 1470 191 670 150 93 30.1 G 1480 190 780 200 94 29.6 H 1475 182 850 220 93.5 27.4 I 1480 190 670 120 94 24,Sample Of Typical 110kW Motors,Maximum motor start current under full voltage start conditions is
6、defined by the motors Locked Rotor Current (LRC). 全电压起动条件下最大电机起动电流是由电机锁定转子电流（LRC）确定的。 LRC levels vary considerably between motors. LRC等级在电机间有显著变化。 In the example, Motor H will draw 55% more current at start than Motor E. 在实例中，电机H引入的起动电流比电机E多55%。,Start Current 起动电流,Motor Speed FLC LRC LRT % FL Torque
7、 (rpm) (amps) (%FLC) (%FLT) Efncy 3xFLC A 1470 191 600 263 93 65.8 B 1475 184 600 190 93.5 47.5 C 1475 191 570 150 92 41.6 D 1480 187 660 190 94.5 39.2 E 1470 185 550 120 92 36 F 1470 191 670 150 93 30.1 G 1480 190 780 200 94 29.6 H 1475 182 850 220 93.5 27.4 I 1480 190 670 120 94 24,LRC ranges from
8、 550% to 850%,Sample Of Typical 110kW Motors,Motor start torque performance is indicated by the motors Locked Rotor Torque (LRT) figure. 电机起动扭矩性能是由电机的锁定转子扭矩（LRT）图表示的。 LRT levels vary considerably between motors. LRT等级在各个电机间有显著变化。 In the example, Motor A produces twice as much torque during start as
9、Motor I. 在实例中，电机A起动时产生的扭矩是电机I的两倍。,Start Torque 起动扭矩,Motor Speed FLC LRC LRT % FL Torque (rpm) (amps) (%FLC) (%FLT) Efncy 3xFLC A 1470 191 600 263 93 65.8 B 1475 184 600 190 93.5 47.5 C 1475 191 570 150 92 41.6 D 1480 187 660 190 94.5 39.2 E 1470 185 550 120 92 36 F 1470 191 670 150 93 30.1 G 1480 19
10、0 780 200 94 29.6 H 1475 182 850 220 93.5 27.4 I 1480 190 670 120 94 24,LRT ranges from 120% to 263%,Sample Of Typical 110kW Motors,LRC & LRT must be considered together when determining a motors start performance. 确定电机起动性能时必须合并考虑LRC & LRT。 The example does this by ranking the motors according to th
11、e torque produced at 3 x FLC. 实例中的作法是根据3FLC产生的扭矩对电机排序。,LRC & LRT Work Together LRC & LRT同时运转,Motor Speed FLC LRC LRT % FL Torque (rpm) (amps) (%FLC) (%FLT) Efncy 3xFLC A 1470 191 600 263 93 65.8 B 1475 184 600 190 93.5 47.5 C 1475 191 570 150 92 41.6 D 1480 187 660 190 94.5 39.2 E 1470 185 550 120 9
12、2 36 F 1470 191 670 150 93 30.1 G 1480 190 780 200 94 29.6 H 1475 182 850 220 93.5 27.4 I 1480 190 670 120 94 24,Sample Of Typical 110kW Motors,Torque developed at 3 x FLC,Motor Speed FLC LRC LRT % FL Torque (rpm) (amps) (%FLC) (%FLT) Efncy 3xFLC A 1470 191 600 263 93 65.8 B 1475 184 600 190 93.5 47
13、.5 C 1475 191 570 150 92 41.6 D 1480 187 660 190 94.5 39.2 E 1470 185 550 120 92 36 F 1470 191 670 150 93 30.1 G 1480 190 780 200 94 29.6 H 1475 182 850 220 93.5 27.4 I 1480 190 670 120 94 24,Torque is reduced by the square of the current reduction. 扭矩减少值是电流降底值的平方。 Motors B & G produce almost the sa
14、me torque at full voltage. 电机B和G在满电压情况下产生的扭矩几乎相同。 Motor B produces 60% more start torque at 3 x FLC. 电机B在3 x FLC条件下产生的起动扭矩多60。,Reduced Voltage Starting Amplifies Motor Differences 降压起动扩大电机差异,Sample Of Typical 110kW Motors,Motor LRC LRT TORQUE (%FLC) (%FLT) 3 X FLC A 600 263 65.8 B 600 190 C 570 150
15、D 660 190,Follow the example and calculate the start torque at 3 x FLC for motors B, C & D. 依照实例，计算电机B、C和D在3 x FLC条件下的起动扭矩。,How To Calculate Start Torque 如何计算起动扭矩,( ),2,65.8%,= x,47.5,41.5,39.3,Selecting a motor with low Locked Rotor Current (LRC) and high Locked Rotor Torque (LRT) will: 选择低锁定转子电流（L
16、RC）和高锁定转子扭矩（LRT）电机将： Reduce start current. - 降低起动电流 Increase start torque. - 增加起动扭矩 Reduce soft starter cost. - 降低软起动器的成本,Summary 总结,Current rises instantaneously to LRC levels. This causes a current transient that can have undesirable effects on the supply. 电流瞬间上升至LRC水平，由此引起的电流瞬变可对电源产生不良的影响 Current gradually falls as motor speed increases. 电机速度增加时电流下降。 Motor loading affects only the time taken for ac
