Motion Control

Variable Frequency Drive

In which cases the energy saving is possible with the help of Variable Frequency Drive?

The energy saving is possible and is of significance only in the following case:

The Variable Frequency Drive is used for operating variable torque load like fans, blowers and pumps.

• It is possible only if the fans, blowers and pumps are working at their partial capacity and not at full capacities.
• It is of significance if Variable Frequency Drive is operating high power load i.e. beyond 20HP, at low power loads like 1HP to 20HP the energy consumption is already less and is of less significance.
• The energy is significant only if the connecting equipment works for considerable operating hours in a year.
• The pressure drop created because of low RPM operation of fans, blowers and pumps should be tolerable to the system.

How much energy saving is possible?
The energy saving in case of fans, blowers and pumps is possible to the extent of 30 % to 60% depending upon the operating point, no. of hrs. per year and the pressure drop tolerable to the system. In case of compressor the energy saving to the extent of 15 to20% is possible depending upon the loading - unloading cycle and operating hrs. per annum of the compressor.

How energy is saved in case of compressor by using Variable Frequency Drive?
The Variable Frequency Drive reduces the no load losses of the compressor motor by reducing the unloading time of operation. It reduces the pressure difference between high cutout pressure and low cut-in pressure by precise speed control of compressor motor and by using PID controller.

What countermeasures are provided against instantaneous power failure?
The VT-240S incorporates a regeneration power ride-through control and auto-restart function, so that it does not trip in case of an instantaneous power failure. Regeneration power ride-through control Continues operation during instantaneous power failure using regenerative energy. You can keep operating the motor without tripping in case of an instantaneous power failure by taking advantage of this function.

Can I connect the power factor improvement capacitor at the input or output of the inverter?
No, You cannot connect power factor improvement capacitors at the inverter's input or output end. Output capacitors can generate high currents containing high frequency components, resulting in the inverter tripping because of over current. This can also have adverse effects on the capacitors. To improve the power factor, insert an input AC reactor (optional) on the inverter's input side.

Where can we connect brake motor?
We can connect brake motor's circuit to the inverter's power supply side because if the braking circuit is directly connected to the inverter's output terminals, the brake cannot be released because of the lowered starting voltage.

What is multi-pump control feature?
Multi-pump control refers to operating up to six pumps (one variable speed control pump, and up to five ON/OFF control pumps) in parallel using five relay outputs provided in the inside of one VT240S. The pressure in the glow passage is controlled to be constant. The pressure step of the ON/OFF controlled pumps is interpolated by a pump which is controlled by the VT240S Variable Frequency Drive, which has the PID control function. This maintains the pressure's continuation. The relay output used for the pump's ON/OFF control are the VT240S standard relay output and the relay interface option relay output.

Automation

Process-PLC

What is the difference between conventional PLC and Process PLC?
The process PLC combines all the characteristics of digital automation along with the digital I/O, analog I/O, PID loops, servo axes, stepper axes, MMI, HMI, networking, data handling and storage with one common programming platform.

What is the scan time of PLC?
Process PLC works on the principle of parallel multitasking, where the scan time is not dependent on the length of program as observed in case of cyclic program. Hence the higher priority functions can be assigned with top priority task, where the scan time can be considered as almost nil (in 2 to 3 milliseconds due to the capacitance effect of the input channel).

What do you mean by interface free program?
The all functionality of Process PLC like PID, Servo, Stepper, analog I/O, digital I/O , networking ,MMI, HMI, interpolation etc can be achieved by one common program SYMPAS only. Hence the interfacing between different software is not required and all the functions can be achieved with real time control basis without any complexity. Chances of interface error are eliminated. Because of this, SYMPAS is called the interface free program.

What do you mean by Simple PLAIN TEXT programming language?
In today's automation industry, many controllers are available having different programming techniques like ladder, statement list, functional charts and plain text. In conventional plain text, the program is based on C or C ++. Hence the complexity of higher-level language is there, which requires special skill and experience of higher level language. However in SYMPAS, all the functionality of higher-level language is there, having plain English basic 26 commands for programming. Which do not require any experience of programming, even worker can also program the PLC within short course of time.

What is multitasking?
In conventional controllers, the program runs in cyclic mode. However the SYMPAS run in multitasking, where the total program split at different loops / sub programs/ tasks, which run parallel on time shared basis. In multitasking where the program is waiting for any events or condition true, the program will not run further till the condition is fulfilled and will not consume the time of CPU. Hence the CPU can efficiently perform the logic compared to cyclic program. Scan time of controller is much lesser and not dependent on length of program compared to conventional controllers.

Which are the process monitoring software available?

• VIADUKT : DOS based process monitoring software with graphic editor, menu structure, dynamics, trend graph, bar graph, message editor , data storage and DA transfer etc.
• JETLINK: Windows NT based software with SCADA facility having full capacity of process monitoring .
• JET WEB: Web based process monitoring software with Ethernet bus technology.

Is interpolation between axes available with PLC?
Yes, Linear and circular interpolation is available with Delta models.

Are the Inputs / Outputs protected?
Yes, They are fully protected from over voltage, over temperature, short-ckt, overload

Is PLC suitable for industry having electromagnetic pollution?
Yes, The inherent design of the PLC is capable enough to absorb the noise generated in industry. All the products are CE approved and fully tested for such heavy electromagnetic noise. The housing is made from metal and the inter-bus communication is CAN bus.

What is the MTBF of your PLC?
50 years

Power Quality

Active Harmonic Filter

What is the operating principle of Active Harmonic Filter?
Active Harmonic Filter senses the load current in totality and generates the ideal reference current. By comparing this reference current with actual non-linear load current the Active Harmonic Filter finds out the harmonic current in the load. The Active Harmonic Filter generates equal and opposite harmonic current and cancels it. Thus the current drawn from source is distortion free sine wave current.

What are the benefits of Active Harmonic Filter other than filtration of Harmonics?
Active Harmonic Filter can improve the power factor to unity; it can also balance the 3-phase currents in case of any un-balance.

What are the main advantages of Active Harmonic Filter over the Passive Harmonic Filter?

• Active Harmonic Filter analyses the load by itself and one need not know the harmonic in the load as in case of passive harmonic filter.
• Active Harmonic Filter is immune to the main frequency variation where as the passive harmonic filter is very much sensitive to the frequency of the mains power.
• Active Harmonic Filter can take care of the changes in the non linearity of the load current where as Passive Harmonic Filter can't take care of the changes in the load current pattern.
• Active Harmonic Filter can filter the harmonics up to 31st harmonic. The Passive Harmonic Filter is very difficult to tune as the harmonics beyond 11th. And it is ineffective in case of harmonics beyond 11th harmonic.

Why do other devices malfunction due to noise?
Using PWM control, the inverter generates noise that may affect nearby instrumentation and electronic equipment. Noise is classified by propagation route into: transmission noise, induction noise. Measures should be taken according to the types of noise. Take the following counter measures for noise, which affects other equipment.

• Separate the signal cables from the power cables with sufficient distance.
• Install noise filters.
• Use twisted-pair shielding cables for weak electric circuits and signal circuits, and be sure to ground one end of the shielding.
• Install the inverters separately from other equipment.
• Cover the inverters and their cables with metal conduit tubes and metal control panels, and ground these covers.