A Variable Frequency Drive (VFD) is a type of engine controller that drives a power engine by varying the frequency and voltage supplied to the electrical motor. Other names for a VFD are variable speed drive, adjustable rate drive, adjustable frequency drive, AC drive, microdrive, and inverter.
Frequency (or hertz) is directly linked to the motor’s speed (RPMs). Quite simply, the faster the frequency, the quicker the RPMs go. If a credit card applicatoin does not require a power motor to run at full rate, the VFD can be utilized to ramp down the frequency and voltage to meet certain requirements of the electric motor’s load. As the application’s motor acceleration requirements alter, the VFD can simply arrive 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 definitely comprised of six diodes, which are similar to check valves found in plumbing systems. They allow Variable Speed Drive current to movement in only one direction; the direction demonstrated 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, after that that diode will open and allow current to movement. When B-stage turns into 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 aspect of the bus. Thus, we get six current “pulses” as each diode opens and closes. That is called 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 program. The 480V rating is “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 get rid of the AC ripple on the DC bus by adding a capacitor. A capacitor operates in a similar fashion to a reservoir or accumulator in a plumbing program. This capacitor absorbs the ac ripple and delivers a easy dc voltage. The AC ripple on the DC bus is typically less than 3 Volts. Therefore, the voltage on the DC bus turns into “around” 650VDC. The actual voltage depends on the voltage level of the AC series feeding the drive, the level of voltage unbalance on the energy 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 referred to as a converter. The converter that converts the dc back again to ac can be a converter, but to tell apart 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 among the top switches in the inverter, that stage of the engine is connected to the positive dc bus and the voltage upon that stage becomes positive. Whenever we close among the bottom switches in the converter, that phase is connected to the negative dc bus and turns into negative. Thus, we are able to make any stage on the engine become positive or adverse at will and can thus generate any frequency that we want. So, we are able to make any phase be positive, negative, or zero.
If you have an application that does not need to be operate at full acceleration, 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 rate of the motor-driven devices to the strain requirement. There is no other approach to AC electric electric motor control which allows you to do this.
By operating your motors at the most efficient speed for the application, fewer mistakes will occur, and thus, production levels increase, which earns your company higher revenues. On conveyors and belts you get rid of jerks on start-up allowing high through put.
Electric motor systems are accountable for a lot more than 65% of the energy consumption in industry today. Optimizing engine control systems by setting up or upgrading to VFDs can decrease energy consumption in your service by as much as 70%. Additionally, the utilization of VFDs improves product quality, and reduces production costs. Combining energy efficiency tax incentives, and utility rebates, returns on purchase for VFD installations can be as little as 6 months.

Your equipment can 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 you better safety for your motor from issues such as electro thermal overloads, stage protection, under voltage, overvoltage, etc.. When you start a load with a VFD you won’t subject the motor or powered load to the “quick shock” of across the collection starting, but can begin smoothly, thereby eliminating belt, equipment and bearing wear. It also is a great way to lessen and/or eliminate water hammer since we are able to have easy acceleration and deceleration cycles.