A Variable Frequency Drive (VFD) is a type of engine controller that drives an electric engine by varying the frequency and voltage supplied to the electric powered motor. Other names for a VFD are variable speed drive, adjustable velocity drive, adjustable frequency drive, AC drive, microdrive, and inverter.
Frequency (or hertz) is directly related to the motor’s quickness (RPMs). Basically, the faster the frequency, the faster the RPMs go. If an application does not require a power motor to perform at full acceleration, the VFD can be used to ramp down the frequency and voltage to meet the requirements of the electrical motor’s load. As the application’s motor speed requirements alter, the VFD can merely 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 comprised of six diodes, which act like check valves used in plumbing systems. They enable current to movement in only one direction; the direction proven by the arrow in the diode symbol. For example, whenever A-phase voltage (voltage is comparable to pressure in plumbing systems) is usually more positive than B or C phase voltages, then that diode will open and invite current to stream. When B-phase turns into more positive than A-phase, then your B-phase diode will open and the A-stage diode will close. The same is true for the 3 diodes on the harmful side of the bus. Thus, 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.
Let us 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 see, the VFD dc bus has a dc voltage with an AC ripple. The voltage operates between approximately 580V and 680V.
We can eliminate the AC ripple on the DC bus with the addition of 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 provides a clean dc voltage. The AC ripple on the DC bus is typically significantly less than 3 Volts. Thus, the voltage on the DC bus turns into “approximately” 650VDC. The actual voltage will depend on the voltage level of the AC collection feeding the drive, the level of voltage unbalance on the energy system, the motor load, the impedance of the energy 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 to ac is also 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 linked to the positive dc bus and the voltage upon that phase becomes positive. When we close one of the bottom level switches in the converter, that phase is connected to the detrimental dc bus and becomes negative. Thus, we can make any phase on the engine become positive or negative at will and can therefore generate any frequency that we want. So, we can make any phase be positive, negative, or zero.
If you have a credit card applicatoin that does not have to be operate at full rate, then you can Variable Speed Drive decrease energy costs by controlling the electric motor with a adjustable frequency drive, which is one of the benefits of Variable Frequency Drives. VFDs enable you to match the quickness of the motor-driven apparatus to the load requirement. There is no other method of AC electric electric motor control that allows you to accomplish this.
By operating your motors at most efficient velocity for your application, fewer errors will occur, and thus, production levels increase, which earns your business higher revenues. On conveyors and belts you get rid of jerks on start-up enabling high through put.
Electric engine systems are responsible for 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 service by as much as 70%. Additionally, the use of VFDs improves product quality, and reduces production costs. Combining energy efficiency taxes incentives, and utility rebates, returns on purchase 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 optimal control of the motor’s frequency and voltage, the VFD will offer you better security for your motor from issues such as electro thermal overloads, phase security, under voltage, overvoltage, etc.. When you begin a load with a VFD you will not subject the motor or driven load to the “immediate shock” of over the range starting, but can start smoothly, thereby eliminating belt, gear and bearing wear. In addition, it is an excellent way to lessen and/or eliminate drinking water hammer since we can have clean acceleration and deceleration cycles.