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A Variable Frequency Drive (VFD) is a type of 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 variable speed drive, adjustable acceleration drive, adjustable frequency drive, AC drive, microdrive, and inverter.
Frequency (or hertz) is directly related 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 perform at full swiftness, the VFD can be used to ramp down the frequency and voltage to meet up certain requirements of the electrical motor’s load. As the application’s motor speed requirements change, the VFD can merely turn up or down the electric motor 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 certainly comprised of six diodes, which act like check valves found in plumbing systems. They allow current to circulation in mere one direction; the direction proven by the arrow in the diode symbol. For instance, whenever A-phase voltage (voltage is comparable 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 stream. When B-phase turns into more positive than A-phase, then the B-phase diode will open up and the A-phase diode will close. The same is true for the 3 diodes on the harmful side of the bus. Therefore, we get six current “pulses” as each diode opens and closes. This is known as a “six-pulse VFD”, which may be 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 certainly “rms” or root-mean-squared. The peaks on a 480V system 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 works in a similar fashion to a reservoir or accumulator in a plumbing system. This capacitor absorbs the ac ripple and delivers a easy dc voltage. The AC ripple on the DC bus is Variable Speed Drive typically significantly less than 3 Volts. Thus, the voltage on the DC bus becomes “around” 650VDC. The real voltage depends on the voltage level 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, may also be 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 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 among the bottom switches in the converter, that phase is linked to the unfavorable dc bus and becomes negative. Thus, we can make any stage on the motor become positive or harmful at will and may therefore generate any frequency that people want. So, we are able to make any phase maintain positivity, negative, or zero.
If you have an application that does not have to be operate at full swiftness, then you can decrease energy costs by controlling the motor with a variable frequency drive, which is among the advantages of Variable Frequency Drives. VFDs enable you to match the acceleration of the motor-driven apparatus to the load requirement. There is absolutely no other method of AC electric engine control that allows you to accomplish this.
By operating your motors at the most efficient velocity for your application, fewer mistakes will occur, and therefore, production levels will increase, which earns your organization higher revenues. On conveyors and belts you get rid of jerks on start-up permitting high through put.
Electric engine systems are responsible for a lot more than 65% of the power consumption in industry today. Optimizing electric motor control systems by setting up or upgrading to VFDs can decrease energy consumption in your service by as much as 70%. Additionally, the use of VFDs improves product quality, and reduces creation costs. Combining energy performance tax incentives, and utility rebates, returns on expense for VFD installations can be as little as 6 months.