CANopen Programmer's Manual - Maccon.de

5: Stepper Mode Support CANopen Programmer’s Manual
Current Control in Microstepping Mode
Servo systems use their servo loops to determine how much current (and in which direction) to
apply to the motor. For a stepper motor, the amount of current is typically a constant value
programmed by the user.
In addition, Copley Controls amplifiers use different current values for different states of motor
activity. During constant speed moves, the Run Current is applied.
During the acceleration / deceleration portion of the move, the Boost Current is used. After a move
completes (the velocity reaches zero) the amplifier continues to apply the Run Current to the
motor for the amount of time programmed in the Run to Hold Time object. Once that timeout has
expired, the Hold Current is applied.
While Boost Current is applied to the motor, an I 2 T limit is used to protect the motor from
overheating. If the move remains in the acceleration phase for longer than the boost current time,
then the current applied to the motor falls back to the run current. This allows the system to set the
Run Current value equal to the motor’s continuous current limit, and set the Boost Current to a
value larger then the motor’s continuous limit.
Once the move has finished and the holding current has been applied to the motor, an optional
voltage control mode of operation can be entered. In this mode of operation, the motor is held in
position with extremely low jitter at the expense of a slightly looser control of the current in the
motor's windings. The Voltage Control Mode Time Delay object can be programmed to control the
delay between entering hold current mode and entering the voltage control mode.
If the Voltage Control Mode Time Delay is set to zero, the voltage control mode is disabled.
160 Copley Controls