A Adjustable Frequency Drive (VFD) is a type of motor controller that drives a power engine by varying the frequency and voltage supplied to the electric powered motor. Other titles for a VFD are variable speed drive, adjustable quickness drive, adjustable frequency drive, AC drive, microdrive, and inverter.
Frequency (or hertz) is directly linked to the motor’s rate (RPMs). Basically, the faster the frequency, the faster the RPMs go. If a credit card applicatoin does not require an electric motor to perform at full acceleration, the VFD can be used to ramp down the frequency and voltage to meet certain requirements of the electric motor’s load. As the application’s motor rate requirements change, the VFD can merely arrive or down the engine speed to meet up the speed requirement.
The first stage of a Variable Frequency AC Drive, or VFD, may be the Converter. The converter is usually comprised of six diodes, which are similar to check valves used in plumbing systems. They allow current to circulation in only one direction; the path proven 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, after that that diode will open and invite current to flow. When B-phase turns into more positive than A-phase, then your B-phase diode will open up and the A-phase diode will close. The same is true for the 3 diodes on the negative side of the bus. Thus, we obtain six current “pulses” as each diode opens and closes. This is called a “six-pulse VFD”, which is the standard configuration for current Adjustable 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 see, the VFD dc bus includes a dc voltage with an AC ripple. The voltage operates 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 delivers a soft dc voltage. The AC ripple on the DC bus is typically less than 3 Volts. Hence, the voltage on the DC bus turns into “approximately” 650VDC. The real 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 to ac is also a converter, but to tell apart it from the diode converter, it is generally known as an “inverter”. It is becoming common in the market to make reference to any DC-to-AC converter as an inverter.
When we close one of the top switches in the inverter, that stage of the electric motor is linked to the positive dc bus and the voltage on that stage becomes positive. Whenever we close among the bottom switches in the converter, that phase is linked to the detrimental dc bus and becomes negative. Thus, we are able to make any stage on the engine become positive or bad at will and may 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 need to be run at full rate, then you can cut down energy costs by controlling the engine with a variable frequency drive, which is among the benefits of Variable Frequency Drives. VFDs permit you to match the acceleration of the motor-driven tools to the load requirement. There is absolutely no other approach to AC electric engine control which allows you to do this.
By operating your motors at most efficient acceleration for your application, fewer errors will occur, and therefore, 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 engine systems are responsible for more than 65% of the energy consumption in industry today. Optimizing engine control systems by installing or upgrading to VFDs can reduce energy intake in your service by as much as 70%. Additionally, the utilization of VFDs improves item quality, and reduces creation costs. Combining energy efficiency tax incentives, and utility rebates, returns on investment for VFD installations can be as little as six months.
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