This article introduces the development concept of the center winding control function of Danfoss FC302 low-voltage frequency converter through actual project debugging practice. This product has excellent performance and high reliability, and is worth promoting and applying.
Center winding function introduction
Figure 1 Schematic diagram of the center winding system
As shown in Figure 1, center winding control consists of three main parts: tension setpoint processing—tension control can vary with the winding diameter; diameter calculation function; and tension PID control. The basic characteristics of center winding are:
The refresh time for tension control is 10-30ms.
Tension-given ramp function
Tension control taper function
Tension limit alarm
Multi-material tension PID parameter set
Speed pidp value adjustment
Acceleration compensation function
Roll diameter arrival indication
Multiple initial roll diameter selections and roll diameter measurement
Roll diameter calculation limitations—the rate of change in roll diameter calculation is adjustable; limitations apply when the roll diameter calculation direction is incorrect.
1. Tension setting processing
Figure 2 Tension setting process
Tension setting, also known as taper control, aims to ensure consistent tension inside and outside the roll during winding, especially when the diameter changes, thus preventing roll deformation during storage. The relationship between tension setting and roll diameter is not linear but hyperbolic.
2. Tension Unit
Figure 3 Tension unit
As can be seen from Figure 3, the actual setpoint of the PID is the setpoint after taking into account the taper function. At the same time, par-194 is a very important parameter that has a great impact on the tension system.
3. Diameter calculation function
Figure 4 Diameter Calculation
Diameter calculation is based on D = linespeed / winderspeed × core1. Multiple initial roll diameters can be selected. Once the roll diameter is reset, the effective roll diameter value is the first initial roll diameter. The calculated roll diameter value remains unchanged when the machine is powered on; after a power outage and subsequent power-on, it is the same as the reset roll diameter.
4. Overall Layout Diagram
Figure 5 Overall Frame Diagram of the Center Winding
The center winding also has manual forward and reverse adjustment functions. Meanwhile, the total setpoint of the frequency converter is the speed setpoint corresponding to the winding diameter plus the PID adjustment amount.
Several important technical parameters
1. Three parameters related to roll diameter calculation
1924: linespeedscale
This parameter is a coefficient that measures the maximum linear velocity relative to the given linear velocity pulse. Its meaning is that when the number of lines per revolution of the linear velocity encoder is fixed, and the machine is operating at its maximum linear velocity, the linear velocity value calculated based on the roll diameter is 100,000.
It can be obtained using the following formula:
1926-winderspeedscale
Similar to 1924, this parameter is adjusted so that the motor speed value in the roll diameter calculation unit is 100000 when the roll diameter is at its minimum, i.e., the motor speed is at its maximum, and the number of lines per revolution of the encoder reflecting the motor speed is determined.
This parameter can also be obtained using the following formula:
1925—speedmatchscale
This parameter determines the speed at which the motor should operate at its minimum winding diameter when the linear speed is at its maximum. This parameter is related to the mechanical transmission ratio, the PID adjustment, and the inverter's maximum speed setting.
The following factors need to be considered:
When the roll diameter is at its minimum, the speed at which the motor should run relative to the maximum linear speed is determined based on the mechanical parameters. This speed is generally 90% of the maximum motor speed set by the frequency converter (parameter 3-03), that is, the maximum adjustment amount left for the PID is 10% of the maximum motor speed. It should also be noted that parameter 1940 (PID output limit) should be set to a maximum of 16384 x 10%.
2. Several parameters related to PID control that require special attention
1941--PI Deffectversesdiameter
This parameter determines the value of the PID's p-value corresponding to the change in roll diameter. When the roll diameter is large, and tension changes necessitate speed adjustments, the adjustment amount of the PID will be smaller than when the roll diameter is small, requiring a smaller p-value. Conversely, when the roll diameter is small, a larger PID adjustment is needed. Figure 6 visually illustrates this relationship.
Figure 6 shows the volume diameter change corresponding to the p-value of pid.
linespeedaccelerationfeedforward
This parameter is used to compensate for tension fluctuations caused by changes in linear velocity. When the linear velocity changes rapidly, if the PID (Programmable Detector) adjustment function is insufficient to maintain tension stability, this function can be considered. The principle is to superimpose a speed adjustment amount related to the linear velocity change onto the PID output. Practice has shown that this function can effectively compensate for these fluctuations.
The p-value of the velocity loop corresponding to the large and small rolls in 1948 and 1949.
These two parameters are the p-values of the PID (speed pid) for empty and full rolls when the motor control mode is speed closed-loop. These values must be determined at the beginning of commissioning using the MCT10 oscilloscope function or the PID debugging interface of the synchronous control card, with both empty and full rolls. The accuracy of these values directly affects the tension stability during large and small roll operations. These two parameters can be used in conjunction with 1941.
The settings for other winding-related parameters are the same as those for the inverter during non-winding control (such as motor parameter settings, AMA , closed-loop speed settings, etc.), and will not be repeated here.
Through debugging and practical experience in some projects, it has been proven that the center winding control function of FC302 is relatively complete, has good performance, and high reliability, making it worthy of promotion and application.
