Emerson unidrive sp User Manual page 258

Safety Product Mechanical
Information Information Installation
Enabling S ramp increases the total ramp time by the period T since an
additional T/2 is added to each end of the ramp in producing the S.
11.21.4 Torque modes
4.08 Torque reference
RW Bi
±USER_CURRENT_MAX %
Parameter for main torque reference. The normal update rate for the
torque reference is 4ms. However if analog inputs 2 or 3 on the drive are
used as the source of the reference, the drive is in closed-loop vector or
servo mode and the analog inputs are in voltage mode with zero offset,
the sample time is reduced to 250μs.
4.11 Torque mode selector
RW Uni
OL 0 to 1
CL 0 to 4
Open loop
If this parameter is 0 normal frequency control is used. If this parameter
is set to 1 the current demand is connected to the current PI controller
giving closed loop torque/current demand as shown below. The current
error is passed through proportional and integral terms to give a
frequency reference which is limited to the range: -SPEED_FREQ_MAX
to +SPEED_FREQ_MAX.
Current
demand
+
-
Active
current
Closed loop vector and Servo
When this parameter is set to 1, 2 or 3 the ramps are not active while the
drive is in the run state. When the drive is taken out of the run state, but
not disabled, the appropriate stopping mode is used. It is recommended
that coast stopping or stopping without ramps are used. However, if
ramp stop mode is used the ramp output is pre-loaded with the actual
speed at the changeover point to avoid unwanted jumps in the speed
reference.
0: Speed control mode
The torque demand is equal to the speed loop output.
1: Torque control
The torque demand is given by the sum of the torque reference and
the torque offset, if enabled. The speed is not limited in any way,
however, the drive will trip at the overspeed threshold if runaway
occurs.
2: Torque control with speed override
The output of the speed loop defines the torque demand, but is
limited between 0 and the resultant torque reference (Pr 4.08 and
Pr 4.09 (if enabled)). The effect is to produce an operating area as
shown below if the final speed demand and the resultant torque
reference are both positive. The speed controller will try and
accelerate the machine to the final speed demand level with a
torque demand defined by the resultant torque reference. However,
the speed cannot exceed the reference because the required torque
would be negative, and so it would be clamped to zero.
258
Electrical Getting Basic
installation Started parameters
US
0.00
US
0
Frequency
reference
P Pr 4.13
I Pr 4.14
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Running SMARTCARD
Optimization
the motor operation
Depending on the sign of the final speed demand and the resultant
torque, the four areas of operation shown are possible.
+ final speed demand
+ resultant torque
+ final speed demand
-resultant torque
This mode of operation can be used where torque control is required, but
the maximum speed must be limited by the drive.
3: Coiler/uncoiler mode
Positive final speed demand:
A positive resultant torque will give torque control with a positive
speed limit defined by the final speed demand. A negative resultant
torque will give torque control with a negative speed limit of -5rpm.
Negative final speed demand:
A negative resultant torque will give torque control with a negative
speed limit defined by the final speed demand. A positive resultant
torque will give torque control with a positive speed limit of +5rpm.
Example of coiler operation:
This is an example of a coiler operating in the positive direction. The final
speed demand is set to a positive value just above the coiler reference
speed. If the resultant torque demand is positive the coiler operates with
a limited speed, so that if the material breaks the speed does not exceed
a level just above the reference. It is also possible to decelerate the
coiler with a negative resultant torque demand. The coiler will decelerate
down to -5rpm until a stop is applied. The operating area is shown in the
following diagram.
-5rpm
Example of uncoiler operation:
This is an example for an uncoiler operating in the positive direction. The
final speed demand should be set to a level just above the maximum
normal speed. When the resultant torque demand is negative the
uncoiler will apply tension and try and rotate at 5rpm in reverse, and so
take up any slack. The uncoiler can operate at any positive speed
applying tension. If it is necessary to accelerate the uncoiler a positive
Onboard Advanced Technical
PLC parameters Data
Current
Pr 4.08
Pr 4.09
Pr 3.01
- final speed demand
+ resultant torque
- final speed demand
- resultant torque
Area for coiler operation, speed
limited to ref and positve torque
Final speed
Torque
demand
Area for decelerating the coiler, reverse
speed limited and negative torque
Unidrive SP User Guide
UL Listing
Diagnostics
Information
+
(if enabled)
Speed
Speed
Issue Number: 13