A Variable Frequency Drive (VFD) is a type of Variable Speed Drive electric motor controller that drives a power motor by varying the frequency and voltage supplied to the electrical motor. Other brands for a VFD are adjustable speed drive, adjustable velocity drive, adjustable frequency drive, AC drive, microdrive, and inverter.
Frequency (or hertz) is directly related to the motor’s speed (RPMs). Basically, the faster the frequency, the faster the RPMs proceed. If a credit card applicatoin does not require an electric motor to perform at full rate, the VFD can be used to ramp down the frequency and voltage to meet the requirements of the electric motor’s load. As the application’s motor speed requirements change, the VFD can merely arrive or down the engine speed to meet up the speed requirement.
The first stage of a Adjustable Frequency AC Drive, or VFD, is the Converter. The converter can be comprised of six diodes, which act like check valves used in plumbing systems. They allow current to flow in only one direction; the path demonstrated by the arrow in the diode symbol. For example, whenever A-stage voltage (voltage is similar to pressure in plumbing systems) can be more positive than B or C stage voltages, after that that diode will open up and allow current to flow. When B-stage turns into 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 harmful part of the bus. Therefore, we obtain six current “pulses” as each diode opens and closes. This is known as a “six-pulse VFD”, which is the standard configuration for current Variable Frequency Drives.
Let us assume that the drive is operating on a 480V power system. The 480V rating is “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 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 fashion to a reservoir or accumulator in a plumbing program. This capacitor absorbs the ac ripple and delivers a even dc voltage. 
The AC ripple on the DC bus is normally significantly less than 3 Volts. Thus, the voltage on the DC bus turns into “around” 650VDC. The actual voltage depends on the voltage degree of the AC collection feeding the drive, the level of voltage unbalance on the power system, the electric motor load, the impedance of the power program, and any reactors or harmonic filters on the drive.
The diode bridge converter that converts AC-to-DC, is sometimes just referred to 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 usually 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 among 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 level switches in the converter, that phase is linked to the detrimental dc bus and becomes negative. Thus, we can make any phase on the electric motor become positive or negative at will and may hence generate any frequency that we want. So, we can make any phase maintain positivity, negative, or zero.
If you have a credit card applicatoin that does not have to be operate at full swiftness, then you can decrease energy costs by controlling the engine with a variable frequency drive, which is among the benefits of Variable Frequency Drives. VFDs enable you to match the velocity of the motor-driven tools to the strain requirement. There is absolutely no other approach to AC electric motor control that allows you to accomplish this.
By operating your motors at most efficient acceleration for the application, fewer mistakes will occur, and therefore, production levels increase, which earns your firm higher revenues. On conveyors and belts you eliminate jerks on start-up permitting high through put.
Electric electric motor systems are accountable for more than 65% of the energy consumption in industry today. Optimizing motor control systems by installing or upgrading to VFDs can decrease energy usage in your service by as much as 70%. Additionally, the utilization of VFDs improves item quality, and reduces production costs. Combining energy effectiveness taxes incentives, and utility rebates, returns on purchase for VFD installations is often as little as six months.
Your equipment will last longer and will have less downtime due to maintenance when it’s controlled by VFDs ensuring optimal motor application speed. Due to the VFDs optimum control of the motor’s frequency and voltage, the VFD will offer better safety for your electric motor from problems such as electro thermal overloads, phase protection, under voltage, overvoltage, etc.. When you begin a load with a VFD you will not subject the engine or powered load to the “instant shock” of over the collection starting, but can start smoothly, thereby eliminating belt, gear and bearing wear. It also is an excellent way to reduce and/or eliminate drinking water hammer since we are able to have clean acceleration and deceleration cycles.