Sigma-II Series SGM*H/SGDH USER'S MANUAL - Esco Drives ...

4 SERVOPACK Specifications and Dimensional Drawings4.5.2 Starting and Stopping Time4.5.2 Starting and Stopping TimeThe motor starting time (tr) and stopping time (tf) under a constant load are calculated using the following formulas.Motor viscous torque and friction torque are ignored.Starting time:Stopping time:tr =tf =• NM (JM + JL)[s]60• (TPM • TL)2π• NM (JM + JL)[s]60• (TPM • TL)2πN M : Motor speed (min -1 )J M : Motor rotor moment of inertia (kg•m 2 )J L : Load converted to shaft moment of inertia (kg•m 2 )T PM : Instantaneous peak motor torque when combined with a SERVOPACK (N•m)T L : Load torque (N•m)Calculate the torque from the motor current using servomotor torque constant × motor current (effective value).The following figure shows the motor torque and motor speed timing chart.Motor torque(current amplitude)trtfTLN MT PMT PMTimeMotor speedTime4.5.3 Load Moment of InertiaThe larger the load moment of inertia, the worse the movement response of the load.The size of the load moment of inertia (J L ) allowable when using a servomotor depends on motor capacity and islimited to within 5 to 30 times the moment of inertia of each servomotor (J M ). This value is provided strictly as aguideline and results may vary depending on servomotor drive conditions.An overvoltage alarm is likely to occur during deceleration if the load moment of inertia exceeds the allowableload moment of inertia. SERVOPACKs with a built-in regenerative resistor may generate a regeneration overloadalarm. Take one of the following steps if this occurs.• Reduce the torque limit.• Reduce the deceleration rate.• Reduce the maximum motor speed.• Install an externally mounted regenerative resistor if the alarm cannot be cleared. Contact your YaskawaApplication Engineering Department.Regenerative resistors are not built into 200 V SERVOPACKs for 30 W to 400 W or 100 V SERVOPACKs for30 W to 200 W. The following figures show the tentative relationship between the load moment of inertia andmotor speed using an example with a load moment of inertia 10 to 30 times the rotor moment of inertia at themotor shaft.External regenerative resistors are required when this condition is exceeded or if the allowable loss capacity (W)of the built-in regenerative resistor is exceeded due to regenerative drive conditions when a regenerative resistoris already built in.4-20