A Adjustable Frequency Drive (VFD) is a kind of engine controller that drives a power electric motor by varying the frequency and voltage supplied to the electrical motor. Other brands for a VFD are variable speed drive, adjustable speed drive, adjustable frequency drive, AC drive, microdrive, and inverter.
Frequency (or hertz) is directly related to the motor’s velocity (RPMs). Put simply, the quicker the frequency, the faster the RPMs go. If an application does not require a power motor to perform at full speed, the VFD can be used to ramp down the frequency and voltage to meet up the requirements of the electric motor’s load. As the application’s motor rate requirements change, the VFD can merely turn up or down the motor speed to meet the speed requirement.
The first stage of a Variable Frequency AC Drive, or VFD, may be the Converter. The converter can be made up of six diodes, which are similar to check valves found in plumbing systems. They enable current to stream in only one direction; the direction proven by the arrow in the diode symbol. For example, whenever A-stage voltage (voltage is comparable to pressure in plumbing systems) is usually more positive than B or C stage voltages, after that that diode will open and invite current to stream. When B-phase becomes more positive than A-phase, then your B-phase diode will open and the A-stage diode will close. The same holds true for the 3 diodes on the negative side of the bus. Therefore, we get six current “pulses” as each diode opens and closes. This is Variable Speed Drive called a “six-pulse VFD”, which may be the regular configuration for current Variable Frequency Drives.
Why don’t we assume that the drive is operating on a 480V power program. The 480V rating is usually “rms” or root-mean-squared. The peaks on a 480V program are 679V. As you can see, the VFD dc bus has a dc voltage with an AC ripple. The voltage runs between approximately 580V and 680V.
We can get rid of the AC ripple on the DC bus by adding a capacitor. A capacitor works in a similar style to a reservoir or accumulator in a plumbing system. This capacitor absorbs the ac ripple and delivers a clean dc voltage. The AC ripple on the DC bus is normally significantly less than 3 Volts. Hence, the voltage on the DC bus becomes “approximately” 650VDC. The actual voltage will depend on the voltage degree of the AC series feeding the drive, the amount of voltage unbalance on the power system, the 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, 
is sometimes just known as a converter. The converter that converts the dc back to ac is also a converter, but to distinguish it from the diode converter, it is normally known as an “inverter”. It has become common in the industry to refer to any DC-to-AC converter as an inverter.
Whenever we close one of the top switches in the inverter, that phase of the engine is linked to the positive dc bus and the voltage on that stage becomes positive. When we close one of the bottom switches in the converter, that phase is connected to the bad dc bus and becomes negative. Thus, we can make any stage on the electric motor become positive or bad at will and may 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 velocity, then you can cut down energy costs by controlling the electric motor with a variable frequency drive, which is one of the advantages of Variable Frequency Drives. VFDs enable you to match the acceleration of the motor-driven devices to the strain requirement. There is absolutely no other method of AC electric motor control which allows you to do this.
By operating your motors at most efficient velocity for the application, fewer errors will occur, and therefore, production levels will increase, which earns your business 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 reduce energy consumption in your facility by as much as 70%. Additionally, the use of VFDs improves product quality, and reduces production costs. Combining energy efficiency tax incentives, and utility rebates, returns on expense for VFD installations can be as little as six months.