YASKAWA G7 Series Technical Manual page 343

Reverse
operation
Torque Limit Operation Examples
Operation examples will be described separately for winding operation, in which the speed and motor torque
are in the same directions, and rewinding operation, in which the speed and motor torque are in opposite direc-
tions.
Winding Operation
In a winding operation, the line (speed) and torque generated by the motor are in the same direction. For the
winding operation, both the speed limit and the torque reference input are positive. The motor will accelerate
when the torque reference input is larger than the load and will decelerate when it is smaller than the load. If
the motor turns faster than the speed limit, a negative compensation value is output from the speed limiter cir-
cuit. When the speed then drops below the speed limit, a positive compensation value is output. The torque
compensation is proportional to the ASR proportional gain. When the sum of the torque reference and the
torque compensation output by the speed limiter is the same as the actual load, the motor will stop accelerating
and run at a constant speed.
Rewinding Operation
In a rewinding operation, the line (speed) and torque generated by the motor are in the opposite directions. (In
this example, we'll assume that the line speed is positive and the torque reference input is negative.) For the
rewinding operation, the speed limit is positive and the torque reference input is negative. If the motor turns
faster than the speed limit, a negative compensation value is output from the speed limiter circuit. If the motor
is rotating in reverse, a negative compensation value is output. If the speed is 0 or is below the speed limit, a 0
compensation value is output. In this way, the output from the speed limiter is used to maintain the motor
speed between 0 and the speed limit. When the sum of the torque reference and the torque compensation out-
put by the speed limiter is the same as the actual load, the motor will stop accelerating and run at a constant
speed.
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Positive torque
Speed limit bias
d5-05
Forward speed limit
50%
Negative torque
Fig 6.65 Speed Limit Bias Setting
Individual Functions
Forward
operation
125
6-