A Variable Frequency Drive (VFD) is a type of engine controller that drives an electric motor by varying the frequency and voltage supplied to the electrical motor. Other brands for a VFD are variable speed drive, adjustable rate drive, adjustable frequency drive, AC drive, microdrive, and inverter.
Frequency (or hertz) is directly related to the motor’s quickness (RPMs). Quite simply, the quicker the frequency, the faster the RPMs proceed. If an application does not require an electric motor to run at full speed, the VFD can be utilized to ramp down the frequency and voltage to meet the requirements of the electric motor’s load. As the application’s motor acceleration requirements modify, the VFD can simply turn up or down the electric motor speed to meet the speed requirement.
The first stage of a Adjustable Frequency AC Drive, or VFD, is the Converter. The converter is usually made up of six diodes, which act like check valves found in plumbing systems. They allow current to circulation in only one direction; the path shown by the arrow in the diode symbol. For example, whenever A-stage voltage (voltage is similar to pressure in plumbing systems) is more positive than B or C stage voltages, then that diode will open up and invite current to movement. When B-stage becomes more positive than A-phase, then the B-phase diode will open and the A-phase diode will close. The same is true for the 3 diodes on the unfavorable part of the bus. Therefore, we obtain six current “pulses” as each diode opens and closes. That is called a “six-pulse VFD”, which is the standard configuration for current Adjustable Frequency Drives.
Why don’t we assume that the drive is operating upon a 480V power program. The 480V rating is definitely “rms” or root-mean-squared. The peaks on a 480V program are 679V. As you can plainly see, the VFD dc bus has a dc voltage with an AC ripple. The voltage runs between approximately 580V and 680V.
We can eliminate the AC ripple on the DC bus by adding a capacitor. A capacitor operates in a similar style to a reservoir or accumulator in a plumbing system. This capacitor absorbs the ac ripple and delivers a simple dc voltage. The AC ripple on the DC bus is typically significantly less than 3 Volts. Therefore, the voltage on the DC bus becomes “around” 650VDC. The actual voltage depends on the voltage degree of the AC series feeding the drive, the amount of voltage unbalance on the power system, the electric motor load, the impedance of the power system, 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 again to ac can be a converter, but to distinguish it 
from the diode converter, it is normally referred to as an “inverter”. It is becoming common in the market to refer 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 connected to the positive dc bus and the voltage on that stage becomes positive. Whenever we close among the bottom level switches in the converter, that phase is connected to the adverse dc bus and turns into negative. Thus, we are able to make any phase on the engine become positive or adverse at will and will hence generate any frequency that we want. So, we are able to make any phase be positive, negative, or zero.
If you have a credit card applicatoin that does not need to be run at full quickness, then you can decrease energy costs by controlling the motor with a adjustable frequency drive, which is among the benefits of Variable Frequency Drives. VFDs allow you to match the swiftness of the motor-driven equipment to the strain requirement. There is absolutely no other method of AC electric motor control that allows you to accomplish this.
By operating your motors at the most efficient quickness for your application, fewer errors will occur, and thus, production levels Variable Speed Drive increase, which earns your company higher revenues. On conveyors and belts you remove jerks on start-up allowing high through put.
Electric electric motor systems are responsible for more than 65% of the power consumption in industry today. Optimizing engine control systems by installing or upgrading to VFDs can decrease energy intake in your facility by as much as 70%. Additionally, the utilization of VFDs improves product quality, and reduces production costs. Combining energy performance taxes incentives, and utility rebates, returns on expense for VFD installations can be as little as 6 months.
Your equipment will last longer and can have less downtime because of maintenance when it’s controlled by VFDs ensuring optimal motor application speed. Due to the VFDs ideal control of the motor’s frequency and voltage, the VFD will offer better safety for your electric motor from issues such as electro thermal overloads, phase security, under voltage, overvoltage, etc.. When you start lots with a VFD you will not subject the engine or driven load to the “immediate shock” of across the line starting, but can begin smoothly, thereby eliminating belt, gear and bearing wear. It also is a great way to lessen and/or eliminate water hammer since we can have even acceleration and deceleration cycles.