A Variable Frequency Drive (VFD) is a type of motor controller that Variable Speed Drive Drives a power electric motor by varying the frequency and voltage supplied to the electrical motor. Other titles for a VFD are adjustable speed drive, adjustable rate drive, adjustable frequency drive, AC drive, microdrive, and inverter.
Frequency (or hertz) is directly linked to the motor’s velocity (RPMs). Basically, the faster the frequency, the faster the RPMs go. If an application does not require a power motor to run at full velocity, the VFD can be utilized to ramp down the frequency and voltage to meet certain requirements of the electrical motor’s load. As the application’s motor acceleration requirements alter, the VFD can simply turn up 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 is certainly comprised of six diodes, which act like check valves used in plumbing systems. They enable current to stream in only one direction; the path demonstrated by the arrow in the diode symbol. For example, whenever A-phase voltage (voltage is similar to pressure in plumbing systems) is definitely more positive than B or C phase voltages, then that diode will open and invite current to circulation. 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 holds true for the 3 diodes on the unfavorable aspect of the bus. Therefore, we get six current “pulses” as each diode opens and closes. This is known as a “six-pulse VFD”, which is the standard configuration for current Adjustable Frequency Drives.
Why don’t we 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 program are 679V. As you can see, the VFD dc bus includes 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 system. This capacitor absorbs the ac ripple and provides a clean dc voltage. The AC ripple on the DC bus is typically less than 3 Volts. Therefore, the voltage on the DC bus turns into “approximately” 650VDC. The actual voltage depends on the voltage level of the AC series feeding the drive, the level 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, is sometimes just referred to as a converter. The converter that converts the dc back to ac can be a converter, but to distinguish it from the diode converter, it is generally known as an “inverter”. It has become common in the industry to make reference 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 linked to the positive dc bus and the voltage on that phase becomes positive. When we close one of the bottom switches in the converter, that phase is connected to the adverse dc bus and turns into negative. Thus, we are able to make any stage on the motor become positive or bad at will and can hence generate any frequency that people want. So, we are able to make any phase maintain positivity, negative, or zero.
If you have a credit card applicatoin that does not have to be operate at full speed, 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 allow you to match the speed of the motor-driven devices to the load requirement. There is absolutely no other method of AC electric engine control which allows you to accomplish this.
By operating your motors at most efficient acceleration for the application, fewer errors will occur, and thus, production levels increase, which earns your company higher revenues. On conveyors and belts you eliminate jerks on start-up enabling high through put.
Electric motor systems are accountable for a lot more than 65% of the power consumption in industry today. Optimizing motor control systems by installing or upgrading to VFDs can decrease energy usage in your facility by as much as 70%. Additionally, the utilization of VFDs improves item quality, and reduces production costs. Combining energy efficiency tax incentives, and utility rebates, returns on investment for VFD installations is often as little as six months.
Your equipment will last longer and can have less downtime due to maintenance when it’s controlled by VFDs ensuring 
optimal motor application speed. Because of the VFDs optimum control of the motor’s frequency and voltage, the VFD will offer you better safety for your engine from problems such as electro thermal overloads, stage protection, under voltage, overvoltage, etc.. When you begin a load with a VFD you will not subject the motor or driven load to the “quick shock” of across the collection starting, but can begin smoothly, thereby eliminating belt, equipment and bearing wear. In addition, it is a great way to lessen and/or eliminate water hammer since we can have soft acceleration and deceleration cycles.