A Variable Frequency Drive (VFD) is a kind of electric motor controller that drives an electric motor by varying the frequency and voltage supplied to the electrical motor. Other names for a VFD are variable speed drive, adjustable acceleration drive, adjustable frequency drive, AC drive, microdrive, and inverter.
Frequency (or hertz) is directly linked to the motor’s swiftness (RPMs). In other words, the faster the frequency, the quicker the RPMs proceed. If a credit card applicatoin does not require an electric motor to perform at full rate, the VFD can be utilized to ramp down the frequency and voltage to meet the requirements of the electrical motor’s load. As the application’s motor quickness requirements alter, the VFD can simply turn up or down the motor speed to meet the speed requirement.
The first stage of a Variable Frequency AC Drive, or VFD, is the Converter. The converter is certainly comprised of six diodes, which act like check valves used in plumbing systems. They enable current to flow in only one direction; the direction shown by the arrow in the diode symbol. For instance, whenever A-phase voltage (voltage is comparable to pressure in plumbing systems) is definitely more positive than B or C phase voltages, then that diode will open up and allow current to flow. When B-phase turns into more positive than A-phase, then the B-phase diode will open and the A-phase diode will close. The same holds true for the 3 diodes on the bad aspect of the bus. Thus, we get six current “pulses” as each diode opens and closes. That is called a “six-pulse VFD”, which may be the standard configuration for current Adjustable Frequency Drives.
Let us assume that the drive is operating on a 480V power system. The 480V rating is definitely “rms” or root-mean-squared. The peaks on a 480V system are 679V. As you can plainly see, the VFD dc bus has a dc voltage with an AC ripple. The voltage operates between approximately 580V and 680V.
We can eliminate the AC ripple on the DC bus with the addition of a capacitor. A capacitor operates in a similar fashion to a reservoir or accumulator in a plumbing system. This capacitor absorbs the ac ripple and provides a even dc voltage. The AC ripple on the DC bus is typically less than 3 Volts. Thus, the voltage on the DC bus turns into “around” 650VDC. The actual voltage depends on the voltage level of the AC line feeding the drive, the amount of voltage unbalance on the power system, the engine load, the impedance of the energy program, and any reactors or harmonic filters on the drive.
The diode bridge converter that converts AC-to-DC, may also be just referred to as a converter. The converter that converts the dc back to ac is also a converter, but to tell apart it from the diode converter, it is usually referred to as an “inverter”. It has become common in the market to make reference to any DC-to-AC converter as an inverter.
When we close among the top switches in the inverter, that phase of the motor is linked to the positive dc bus and the voltage on that phase becomes positive. Whenever we close one of the bottom level switches in the converter, that phase is linked to the detrimental dc bus and becomes negative. Thus, we are able to make any phase on the motor become positive or adverse at will and can thus generate any frequency that people want. So, we can make any phase maintain positivity, negative, or zero.
If you have an application that does not need to be operate at full rate, then you can decrease energy costs by controlling the engine with a adjustable frequency drive, which is among the benefits of Variable Frequency Drives. VFDs enable you to match the speed of the motor-driven apparatus to the strain requirement. There is no other method of AC electric electric motor control that allows you to do this.
By operating your motors at the most efficient acceleration for your application, fewer mistakes will occur, and thus, production levels increase, which earns your company higher revenues. On conveyors and belts you eliminate jerks on start-up allowing high through put.
Electric motor Variable Speed Drive systems are accountable for a lot more than 65% of the energy consumption in industry today. Optimizing electric motor control systems by setting up or upgrading to VFDs can reduce energy usage in your service by as much as 70%. Additionally, the utilization of VFDs improves item quality, and reduces 
creation costs. Combining energy performance taxes incentives, and utility rebates, returns on expenditure for VFD installations is often as little as 6 months.
