Omron VARISPEED F7 User Manual page 308

Speed Limit Bias Setting
The speed limit bias can be set to limit both the forward and reverse speed to the same value. This differs from
the operation of the speed limit setting. To use the speed limit bias, set d5-04 to 0 and set the bias in d5-05 as a
percentage of the maximum output frequency.
To set 50% forward and reverse speed limits, set the speed limit setting to 0 (d5-03 = 2, d5-04 = 0, and d5-05
= 50). The range of torque control will be from -50% to 50% of the maximum output speed.
When using both, the speed limit and the speed limit bias, the speed range of torque control will be the posi-
tive and negative speed limits with the speed limit bias added to each.
Example
The speed range of torque control when the forward speed limit is 50% and the speed limit bias is 10% is
shown in Fig 6.87. This figure does not take the priority circuit into account.
Reverse
operation
Torque Control 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, it is assumed 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 positive 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-
Positive torque
Speed limit bias
d5-05
Forward speed limit
50%
Negative torque
Fig 6.87 Speed Limit Bias Setting
Forward
operation
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125
6-