Textilný priemysel

Application of SLANVERT Inverter in Upgrading of Textile Machinery

I  Inverter Upgrading of Carpet Machine
This carpet machine is an American 1980s product. The whole controlling structure is simple, and the automation level is low. Operators of this machine have to be in high-labor-intensity. Referring to the controlling principle of the latest imported textile machinery, some upgrading is made as following:

A SLANVERT SB70G Series 15kW Inverter (with braking resistor) is chose to synchronize two 5.5kW shaft motors. We use Siemens LOGO! 24RC is adopted as the core logic controller with Omron photoelectric switch, Schmersal safe pull-wire switch and German P+K proximity switch to assist control operations, such as starting, stopping, alarming, full-yarn and doffing, etc.

1. Working process of inverter speed control
Textile machine needs a slow start, slow stop, breakage and an accurate stop in full-yarn process.

2. Start/stop process realization
A 2s-warning will be provided before starting to work. Before starting up, a 60db buzzer will sound for 2s to warn operators taking their hands out of the needle working area. Set start frequency to 6Hz, raise start torque a little and add the other function of the inverter that is S curved line, into the start process to solve the common problem of burning motor while starting as well as avoiding thin place and end breakage.
S curved line slowdown process is used when breakage stop, full-yarn stop or safety stop happens. There is a special requirement for roving frame stop, i.e. flyer positioning stop. When the machine stops, the flyer has to stop at the same position every time and needles leave the cloth layer hanging on 3mm above the cloth (the accuracy range is under 1%) for operation. This technical key point is overcome by the programmable input/output posts of inverter and the PLC programming.
Here is the specific process: when the slowdown stop of the inverter reaches the set 6Hz frequency, programmable relay shall send a signal to the PLC, then the PLC judges the signal and sends the inverter a jog signal to keep 6Hz low speed for a certain time. Now, the photoelectric switch is starting to work. It shall detect the position monitoring point set on the flyer wheel then send output switch signal to the PLC. The PLC counts one, when the wheel rotates one lap,. When counts two, the PLC shall send the inverter a signal to shut the output off and the electromagnetic clutch takes action.

3 Inverter jog realization
Another characteristic of the carpet machine is its frequent jogs. Under low speed operation, the jog of the carpet machine can be realized by pushing the jog button, and the machine shall run in a certain frequency and stop in any position.

4 Emergency stop system
When upgrading this equipment, many functions are added: safe pull-wire switch is set at both the front and the back of the machine. If it is emergent, the machine can be stopped quickly by manual operation. Optical fiber photoelectric sensor is chose to inspect the breakage. If there is a breakage, the thread flies over the photoelectric area then the photoelectric switch takes action to send a signal to the PLG and the PLG gives warning as well as shuts the machine off.

II  Effect Analysis
After upgrading, the motor of the machine runs steadily. The quality of the carpet improves obviously, and the machine will not shut off any more. Meanwhile, the safety system is more effective, and the labor-intensity reduces a lot.


Application of SLANVERT SB80B Inverter in Stenter

I   Introduction
During the scouring, bleaching, printing and dyeing process, the textile undergoes many mechanical longitudinal tensile strength, which makes it extend longitudinally and shrink horizontally. The uneven width, irregular cloth edge and skewed waft yarn would occur. In order to avoid the above defects, the textile must be stentered. Pin chain stenter is the machinery to stenter and it is composed of cloth-in rack, padder, weft straighteners, drying cylinder, hot air dryer and doffing rack. Primary link and secondary link are respectively driven by two AC asynchronous motors. PLC is used to measure the position deviation and calculate the output frequency, so as to control the two inverters to reach the synchronous position. The main disadvantages of the solution are that PLC should be equipped with high-speed counting module, and time delay of the communication control makes the system response not so fast. SLANVERT SB80B inverter introduced in this article can realize synchronous position of the two links without adding any control equipment.

II  System Design
Since the position accumulation error should be avoided, position must act as a feedback signal to control inverter to eliminate the accumulation error. Therefore, pulse coders should be installed on the primary and secondary motors and SB80B high-speed counter is used to count the pulse of the coders, so as to record the deviation in this position. Two inverters are used to drive the two motors. The primary inverter can run at open loop, and can amend the output frequency continuously based on the position deviation from the PID frequency amendment function, so as to reach the synchronous position.
The following diagram is the implementation schematic by using the SB80B to realize synchronous position:

Fig. 1 Implementation Schematic for Synchronous Position of Primary/Secondary Links of Stenter

Other parts of the stenter’s drive system need to change in proportion with primary drive speed, which can be set by communication after a common PLC calculation. The following is the implementation diagram of the system:

Fig. 2 Electric Drive System of Stenter

Human-machine interface is the equipment of input system control parameter. Based on the parameter set by the human-machine interface, PLC sends the control command to each inverter through serial port, such as setting speed of primary link, control command, etc.; two motors on the secondary link are respectively driven by the two inverters and primary inverter is controlled by V/F at open loop. Drive device of the primary motor is connected with the PG, and A of PG signal is connected with A- post on the encoder’s interface of primary inverter. Secondary inverter is also controlled by V/F at open loop, and PID is chosen to amend the speed. A of PG signal of the drive device on secondary motor is connected with B- post on the encoder’s interface of secondary inverter. High speed counter is activated; then, if the speed of the primary link is higher than that of the secondary link, value of the counter will increase; otherwise, the value will decrease. Counting deviation represents the position accumulation error between two links. If the deviation is greater than 0, the primary link is in front of the secondary; otherwise, the primary link is in the back. After treated by the arithmetic unit, counting deviation is input as PID feedback (PID setting value is 0, which means target of the regulation is to eliminate position deviation) and it will be added to the output frequency of the inverter after PID regulation. Motors’ operation frequency of other parts in the system will be calculated by PLC in accordance with the output frequency of the primary inverter.

III  Conclusion
This solution achieves the high-accuracy position synchronous control only with inverter. The system composition is simple with high accuracy and low cost, and operation is stable and reliable. Compared with the top-grade PLC+ inverter used by the system before, it has the following advantages:
Only to set the function code of the inverter; high-speed counting module need not to be added to the PLC and complicated PLC control program need not to be prepared.
Since the amendments are finished in the inverter, control delay time is shorter, response is faster and amendment accuracy is higher.
Low cost. Only a common PLC with communication function is needed in the whole system, and no high-speed counting module is required.


Application of SLANVERT SB70 Inverter in Spinning Frame

I  Introduction
During the spinning production, one of the factors affecting the yarn quality is the impact at the start, stop and jog operation. For the traditional spinning frame, the impact is larger when the motor directly starts, and speed regulation is realized by changing gears with different tooth number while stepless speed regulation can not be realized. AC variable frequency technology is widely applied in the new spinning frame, which solves the problem of impact and speed regulation at the start and stop. Therefore, it is a trend to transform the original equipment with variable frequency technology to improve their technical performance.

II  Transformation Solutions
The rated rotation speed of the spinning frames  1440r/min, and the power is 15kW, operating current is around 15A. The solution is to install a SB70G15 inverter between the power supply and the motor. With help of the V/F control mode, acceleration time and deceleration time of the inverter are set to 20s, which can eliminate the impact at the start and stop by accelerating or decelerating the speed within 20s. Besides, the process change requires the speed regulation, and it is easy to be achieved on the keypad of the inverter. The transformation is easy with lower cost, and the transformation speed is fast without influencing the production.

III  Motor Efficiency
From working conditions of the spinning frame’s motor: 15kW motor with operating current around 15A and the load rate is around 50%, superficially, the energy-saving space seems greater. Actually, output frequency of the inverter still is 50Hz to avoid the influence to production efficiency of the spinning frame. Even though the process change requires the speed regulation, big regulation scope can not be achieved. Besides, the spinning frame has property of constant torque loads, and the energy-saving space is limited as reducing the frequency on a small scope. The energy–saving effect is not so obvious with parameter F2-11=1 (automatic energy-saving operation) of SB70 series inverters by applying voltage regulation function. The similar speed regulation is the requirement of the process, and energy-saving is secondary.