The variable speed drives (Inverter) are designed to operate induction motors which can be added to the existing system easily. They are available in capacities rating from fractional to 750 KW. The basic function of an inverter is to convert the 50 Hz incoming power to a variable frequency and variable voltage. The variable frequency is the actual requirement which controls the motor speed. There are three major types of inverter design available today known as Current Source Inverters (CSI) , Variable Voltage Inverters (VVI), and Pulse Width Modulated Inverters (PWM). They are used for various applications as per the plant/process requirement. The advantages of the variable frequency drive are given below.

Advantages Of Variable Frequency Drive

1. With the help of variable frequency drive (VFD) step less, precise, stable and accurate variation of motor speed can be obtained.

2. Motor can be protected against over current, single phasing, earth fault and over temperature, by tripping the drive under these conditions.

3. Motor can be started smoothly, with no inrush current, no mechanical jerk and without sacrificing the starting torque.

4. Even if input power voltage is unbalanced, the output voltage of VFD is balanced, this avoids derating of motor due to unbalanced input voltage.

5. VFD frequency does not fluctuates even if mains frequency is varying, hence derating of motor due to frequency fluctuations is not required.

6. Motor can be stopped smoothly, by ramping down the VFD frequency, thus jerks to the motor and connected load, during stopping are avoided.

7. Motor can be accelerated or decelerated smoothly and at controllable rates. S-curves can be used during acceleration or deceleration. This avoids jerks to the motor and to the loads connected to it.

8. Dynamic braking provided in VFD helps in stopping the motor rapidly without mechanical jerks, as in case of rapid stopping through mechanical brakes.

9. Magnetic losses in motor can be saved, when it runs on light load, buy programming the VFD, so that its V/F reduces under light loading conditions.

10. VFD input maintains high power factor even if motor runs at light load resulting in poor power factor at its output.

How the disadvantages of Motor Supplied From VFD are overcome?

1. Introduction of VFD injects harmonic currents in mains. This disadvantage can be overcome by using harmonic filters, by using PWM converter in place of conventional diode rectifier, by using multi-pulse converter in place of 6-pulse converter at the input of VFD.

2. VFD output is non-sinusoidal and rich in harmonic content, it can overheat the motor. Extra-heating due to PWM waveform of output voltage of VFD, is not that prohibitive, so as to damage the motor. Even this can be avoided by providing sinus filter at the output of the VFD.

3. Introducing VFD between motor and mains leads to insertion loss of 2% to 3% as VFD itself has some losses.

Yes, but VFD improves motor efficiency by reducing the magnetic losses and due to improved power-factor, improves overall efficiency, this is why VFD has attractive returns on investment in most of the applications.

To conclude, use of VFD has many advantages in industrial applications of induction motors apart from just speed control.

FREQUENCY INVERTER

INDUSTRIES

• Cement

• Chemical

• Food & Drink

• Iron & Steel

• Machine Tool

• Material Handling

• Metal

• Packaging

• Paper & Tissue

• Petroleum

• Pharmaceutical

• Plastic & Rubber

• Power Plant

• Textile

• Wood & Paper

APPLICATIONS

• Agitator

• Blower

• Carding & Looming

• Conveyor

• Fan & Pump

• Geared Machine

• HVAC System

• Lift, Crane & Hoist

• Mixer & Extruder

• Paper Machine & Reelers

• Rolling Mill

• Test Bench

• Winding & Coiling

• Wire Drawing

AXPERT AC DRIVES (High Power)

FEATURES

Models : 50HP to 1000HP

• New Generation IGBT power inverter

• Control strategy - S PWM

• Power loss ride through for 2 seconds

• Slip compensation

• True OL & GF protections

• Closed loop control

• Customize software solutions like traverse, ring frame, energy meter

APPLICATIONS

• Rayon spinning

• Agitators

• Centrifuge

• Paper & Pulp

• Air compressors

• Pumps & Fan

AXPERT - VT230S AC DRIVES (Low Power)

FEATURES

Models upto 60HP (45KW)

• Soft Sound software

• New generation IGBT base

• PWM technology

• 150%  overload

• Dynamic V/F

• 100% Dynamic Breaking

• Catch on fly

• Static potentiometer

• PLCT for 1sec.

• Built in pattern generation

• Built in PID

APPLICATIONS

• Extruders, Blower

• Lifts, elevators, cranes

• Printing, Packing

• Knitting, Ring Spinning

• Centrifuge

• Calendar, Paper machine

SOFT STARTER

FEATURES

Models upto 1000HP

• Torque booster (kickstart)

• Automatic energy optimization

• Current limit

• Electronic overload

• Shear pin protection

• Bypass

APPLICATIONS

• Over head cranes

• Centrifuge / fans

• Compressors / chillers

• Escalators / conveyors

• Pumps

• Ball mills

• Die grinder

AXPERT - HF 2

FEATURES

Models : 3HP to 200HP

• 4x20 LCD display

• 200% overload

• Output frequency upto 3000 Hz

• Area gap eliminator

• Silent operation

• Resolution 0.01 Hz

APPLICATIONS

• Internal grinding

• Surface grinding

• Lens polishing

• Crank pin grinder

• Centre less grinder

• Die grinder

PROCESS - PLC

FEATURES

Models : NANO, MIKRO, DELTA,

PASE-E

• Plain text language

• Multitasking

• Interface free programming

• Networking system software

• Man-machine interface

• Drive for image processing

APPLICATIONS

• Textile manufacturing

• Packaging technique

• Winding machinery

• Semiconductor Manufacturing

• Handling

• Process engineering

MEDIUM VOLTAGE AC DRIVE

FEATURES

Models : Range 150-2000KW Voltage 2 - 13 KV AC

• No motor derating

• Built in harmonic converter

• Adaptable to floating networks

• No limit on cable lengths

• Sinus filter

• High starting torque

APPLICATIONS

• Pumps/Fans

• Water Treatment

• Metal Industry

• Compressors

• Paper Industry

• Oil & Gas Industry

• Power plants