Chapter 2 Installation and Storage2-12 Revision June 2010(2) With LoadWhen there is an external load torque, servo motor is in reverse rotation when externalload greater than motor torque. Servo motor is usually in forward rotation and the motortorque output direction is the same as the rotation direction. However, there is still somespecial condition. If the motor output torque is in the reverse direction of rotation, theservo motor is also in the reverse direction of rotation. The external power is input intothe servo drive through servo motor. The figure below is an example. The users can seethe motor is in forward rotation at constant speed when a sudden external load torquechange and great power is transmitted to regenerative resistor rapidly.Motor Rotation SpeedExternal Load TorqueMotor Output TorqueReverseRotationReverseRotation ForwardRotationForwardRotationExternal load torque in reverse direction: TL x Wr TL : External load torqueFor the safety, we strongly recommend the users should select the proper resistance valueaccording to the load.For example:When external load torque is a +70% rated torque and rotation speed reaches 3000r/min,if using 400W servo drive (rated torque: 1.27Nt-m), then the users need to connect aexternal regenerative resistor which power is 2 x (0.7 x 1.27) x (3000 x 2 x π/ 60) = 560W,40Ω.
