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Chinese New Year 2023 Office Closure Notice

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Chinese New Year 2023 Office Closure Notice

To,

All Valued Customers & Associate Business Partners

RE: CHINESE NEW YEAR 2023 OFFICE CLOSURE NOTICE

In conjunction with the coming Chinese New Year celebration, we would to inform you that our office will be closed from 20th January 2023 (Friday, 1.00pm) to 26th January 2023 (Thursday).

We will resume our operation on 27th January 2023 (Friday).

We take this golden opportunity to thank you for your valuable support and looking forward a growth in business substantially together.

May the Year of Rabbit bring Prosperous and Health in Year 2023
Happy Chinese New Year!!

 

Yours faithfully,

George, Ku Ei Chee

Managing Director

Why is IGBT used in VFD?

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Why is IGBT used in VFD?

What is IGBT?

IGBT is a type of transistor. Basically, the family of transistors consists of three main types – BJT (Bipolar Junction Transistor), FET (Field Effect Transistor), and IGBT (Insulated Gate Bipolar Transistor).

IGBT is a more advanced type of transistor. As a standard construction of a transistor, it too has three terminals – gate, collector, and emitter.

When voltage is applied to the gate, it opens and allows the current to flow between the collector and emitter. When voltage is removed from the gate, it closes and blocks the current to flow between the collector and emitter.

In this way, an IGBT behaves like a switch; on when the gate is open and flowing current and off when it is closed.

IGBT is a combination of BJT and FET. It has the gate function of FET and the low saturation voltage/output characteristics of a BJT. That is why you can see it in its name too; it is a combination of both FET (IG) and BJT (BT). It is capable of handling large collector-emitter currents with virtually zero gate current drive.

Why is IGBT used in VFD?

Coming to the main topic, it must be confusing for you because each type of transistor has its separate characteristics. But, it is important to know that the highest level of advantages are offered in an IGBT.

Let us understand step by step why an IGBT is used in VFD.

  1. VFD is used to provide variations in voltage and frequency to control the motor speed. As the IGBT can act as a switch, it will act so rapidly that it can instantly create pulsating (on and off) waveforms. This is called a PWM (pulse width modulation) waveform. Depending on the output you require, you can control the switching rate of the IGBT. If the gate is opened and closed slowly, then you will get a slow frequency and if the gate is opened and closed quickly, then you will get a fast frequency. This is the first basic requirement of a VFD. And you get this easily from an IGBT.
  2. Now, let us focus on the main advantages of an IGBT over other semiconductors. BJT can be used at higher voltages, but it has a slow switching frequency. MOSFET can be used at higher switching frequencies, but it has a lower voltage rating. But, IGBT can be used at both higher voltages and higher frequencies. Continuing this, IGBT can thus be used for higher collector current exceeding 100A. And if this is inadequate, two or more IGBTs may be paralleled quite easily.
  3.  The voltage drop and conduction loss are lesser in IGBT as compared to other semiconductors.
  4. The IGBT has a much lower “on-state” resistance, RON than an equivalent MOSFET. This means that the I2R drop across the bipolar output structure for a given switching current is much lower. This means that it has a much lower on-state channel resistance than a standard MOSFET; which automatically increases the current ratings.
  5. The IGBT has a fast switching speed. This minimizes switching losses and allows for high switching frequencies which are good for motor harmonic and noise reduction.
  6. A VFD IGBT can turn on in less than 400 nanoseconds and off in less than 500 nanoseconds. This itself is enough for you to imagine how fast it works.

In this way, we understand the use of IGBT in a VFD.

Source: <https://instrumentationtools.com/why-is-igbt-used-in-vfd/>

Effects of Long Distance Cables between VFD and Motor

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Effects of Long Distance Cables between VFD and Motor

The Variable Frequency Drive (VFD) is a very important element in motor speed control. You can get any desired speed with the use of VFD.

But, do you know that the distance between a motor and a VFD matters too? It may not sound too interesting, but it is a fact that the distance between the motor and the VFD is one of the important factors in running a motor efficiently and for longer life.

In this post, we will learn the effect of the long distance between VFD and motor, and why it must be avoided.

Why must the distance between the Motor and VFD be Shorter?

It must be noted that the typical distance between VFD and the motor should not exceed 30 meters. Why? Let us get into the fundamentals now. The output of VFD is a sine wave. For a variable sine wave to properly control the speed of the motor, the cables, VFD, and motor must all be properly grounded. This is the very first step in the topic.

Now, as we are discussing the cable length, the cable must be properly shielded in its very first place. If the cable is properly armoured and grounded, then the noise generated within the cable is confined to itself only.

Otherwise, the noise will be disbursed outside the cable too, and the higher the noise, the higher will be the leakage current generated. And if the distance is long, then the noise will spread over more area, and the chances of the motor getting damaged will increase more. So, this is the very first step in distance point – the cables must be properly grounded, be they shorter or longer distances.

Now, let us move on to the next point. It is to be noted that a capacitance always exists in the sine wave current (PWM signal) flowing in VFD cables to the motor. One of the main issues faced in this is voltage reflection. When the distance is long, the impedance of the power cables and the motor is not consistent. It is mostly consistent in shorter distances.

Now, if a normal PWM signal is flowing and if this impedance collides with it, then there will be high chances of voltage reflection. Impedance plays a very important role in PWM signals. When the drive sends output sine waves down the cable to the motor, they reach the motor and due to the motor’s impedance, reflect back towards the drive, while the drive is continually sending sine waves to the motor.

Coming back to the earlier point of the effect of capacitance, the capacitance from the cables (phase to ground) too can create enough current to ground where there can be nuisance ground fault trips.

These two factors – capacitance and voltage reflections due to improper impedance, can cause the reflected wave could be added to the fundamental waveform coming from the drive resulting in a significantly higher voltage at the motor terminals.

So, if the distance is longer, then there will be more chances of unbalanced voltage peaks in between (due to the issue discussed earlier). This will also increase rise steepness (dv/dt) to a large extent. If the rise is more and unstable, then the voltage peaks will occur frequently.

Both the maximum value of the voltage pulse and the rise steepness (dv/dt) are dangerous for the motor insulation. Due to this, the motor will not operate properly, and also, after a certain period of time, the insulation and bearings of the motor will get damaged.

The long-distance connection will generate surge voltage at both ends of the motor winding, the superimposed surge voltage will increase the winding current of the motor and the motor temperature, thus damaging the winding insulation.

This shows that the distance between VFD and the motor must be tried to keep not too long. There are many ways to counter this; because suppose you are placing a VFD in the central room, then the motor will always be at a larger distance at the field site. It is a completely different topic, and we cannot elaborate here. Our main purpose was to first understand the effect of the long distance between the VFD and the motor.

In this way, we understand the effects of long-distance cables on VFD and motor.

Source: <https://instrumentationtools.com/effects-of-long-distance-cables-between-vfd-and-motor/>

Difference between Soft Starter and VFD

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Difference between Soft Starter and VFD

Soft Starter

The electrical system experiences heavy stress when we start a large rating motor on DOL or star delta. The driven equipment also experiences heavy mechanical stress.

To mitigate the above situation, a soft starter is used for the jerk-less starting and stopping of an induction motor.

Advantages of Soft Starter

The advantages of the use of a soft starter are as follows.

  1. Reduced mechanical stress on the motor and driven equipment
  2. Reduced electro-mechanical stress on the power system
  3. Increased life of the motor

Limitations of the soft starter

The soft starter can be used for starting and stopping the motor at a reduced voltage in order to reduce the starting current for jerk-less starting.

We can not use the soft starter for speed regulation purposes.

Working Principle of Soft Starter

The soft starter has anti-parallel SCR in each phase. The output voltage of each phase is controlled using the controlling firing angle. As the firing angle is reduced the output AC voltage increase.

At starting, the SCRs are fired at a maximum firing angle in order to get low output.

More importantly, the output of the soft starter at the reduced voltage has the same frequency. The soft starter does not change the frequency. The flux in the motor is proportional to the ratio of voltage and frequency.

The V/f ratio is low when the motor is started at low voltage. The starting torque of the motor is low when it is started with a soft starter.

Therefore, the soft starter is suitable for those applications where starting torque requirement is low. If the starting torque requirement is high, the soft starter will draw a large current and may trip with an overcurrent fault.

When the motor achieves its rated speed the bypass contactor is made to bypass the SCRs in order to supply a perfect sinusoidal voltage to the induction motor.

Variable Frequency Drive (VFD)

VFD does two functions.

  1. Soft starting and stopping of an induction motor
  2. Speed control of the motor as per process requirement

The speed of an induction motor is proportional to the frequency and inversely proportional to the number of poles.

Ns = 120f/p

The VFD has the following sections.

  1. Converter section
  2. DC Bus
  3. Inverter section

Three-phase AC voltage is first converted into DC voltage. The output of the rectifier is further filtered to remove the AC components in the DC. The DC voltage is again converted into AC by PWM technology.

The PWM inverter controls the width of the pulse and as a result, the output voltage gets varies with an increased frequency. Thus the V/f ratio of the inverter output is maintained constant.

The motor is capable to deliver the constant torque from minimum speed to base speed of the motor.

The VFD is popularly used in industries for fan and pump applications. The power drawn by the fan and pump is proportional to the cubic speed. Thus, at reduced speed, substantial power saving can be achieved.

Comparison between Soft Starter and VFD

The below comparison table shows the brief differences between the soft starter and VFD drives.

We have to use the VFD drives if the process application requires speed control of the motor as a soft starter does not have this capability.

Source: <https://instrumentationtools.com/difference-between-soft-starter-and-vfd/>

Applications of Variable Frequency Drive (VFD)

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Applications of Variable Frequency Drive (VFD)

The AC drive has been around only since the 1970s. The growing popularity of AC drives is due chiefly to their ability to provide adjustable speed control with standard NEMA B design squirrel cage motors.

Other names for AC drives are variable frequency drive (VFD) and variable speed drive (VSD), but we’ll just call them AC drives.

How do AC Drives work?

A variable frequency drive (VFD) is a type of motor controller that drives an electric motor by varying the frequency and voltage of its power supply.

The VFD also has the capacity to control the ramp-up and ramp-down of the motor during start or stop, respectively.

Applications of Variable Frequency Drive

In this post, we will have a look at some general target industries and applications where the VFD is used.

Some of the industries are mentioned below where we use variable frequency drives.

 

Automotive Industry

The VFDs are used for the following machines.

  1. Conveyors
  2. Tool Changers
  3. Transfer Lines
  4. Boring / Cutting Machines
  5. Feeders
  6. Pressers
  7. Welders
  8. Shears
  9. Parts Positioning
  10. Hoists
  11. Pumps
  12. Ventilating Fans
  13. Grinders
  14. Deburring Equipment
  15. Wind Tunnels

 

Food and Beverage Industry

Following is the equipment that we use VFD in the food industry.

  1. Conveyors
  2. Filling Machines
  3. Capping Machines
  4. Labeling
  5. Wrapping
  6. Pumps
  7. Cutting Process
  8. Fans
  9. Transporters for Freezing Tunnels
  10. Screw Pumps
  11. Crunchers
  12. Mixers
  13. Dough Machines
  14. Agitators

 

Chemical Industry

Here is the list of equipment used with AC drives in the chemical industry.

  1. Centrifugal Pumps
  2. Fans
  3. Dosing and Metering Pumps
  4. Granulators
  5. Mixers
  6. Container Handling
  7. Agitators
  8. Packaging Machines
  9. Dosing Conveyors
  10. Crunchers

 

Textile Industry

The following are the machines used in the textile industry with variable speed drives.

  1. Bobbin Winder
  2. Texturing Machines
  3. Gear Pumps
  4. Mixers
  5. Extruder
  6. Twister and Doubler
  7. Drawing Roller
  8. Washers
  9. Conveyors
  10. Beam Wrappers
  11. Carding Machines
  12. Presser Frames
  13. Knitters
  14. Weaver’s Loom
  15. Dryers
  16. Picking Machines
  17. Flocking Machines
  18. Printing Machines
  19. Scrappers
  20. Bag Handling Machines
  21. Screw Pumps
  22. Sewing Machines
  23. Cutting Machines
  24. Washing Machines
  25. Dry Cleaning
  26. Ironer
  27. Transporters

 

Paper Industry

A short list of machines used with VFDs in the paper industry.

  1. Feeders
  2. Crushers
  3. Centrifugal Pumps
  4. Dryers
  5. Winding / Unwinding Rollers
  6. Coating Machines
  7. Conveyors
  8. Cutting Machines
  9. Unwinding Machines
  10. Glue Pumps
  11. Packaging Machines
  12. Cutting Machines
  13. Ink Pumps
  14. Printing Press
  15. Assembling Machine
  16. Folders

 

Wood Industry

Some more list of equipment in the wood industry used with the drives.

  1. Saws
  2. Ventilating Fans
  3. Pumps
  4. Chip Conveyors
  5. Transfer Cars
  6. Grinders
  7. Saws
  8. Conveyors
  9. Washers
  10. Oven Conveyors
  11. Material Conveyors

 

Metallurgy Industry

The applications of VFDs in the metallurgy industry are mentioned below.

  1. Injectors
  2. Crushers
  3. Conveyors
  4. Pumps
  5. Fans
  6. Wire Drawing Machines
  7. Steel Rolling Machines
  8. Press and Cutting Machines
  9. Plastic Covering Machines
  10. Metal Finishing Treatment
  11. Stitch Seam Welding Machines

In this way, we understand some general applications of VFDs in industries.

Source: <https://instrumentationtools.com/applications-of-variable-frequency-drive-vfd/>