A Adjustable Frequency Drive (VFD) is a type of motor controller that drives a power electric motor by varying the frequency and voltage supplied to the electrical motor. Other titles for a VFD are variable speed drive, adjustable speed drive, adjustable frequency drive, AC drive, microdrive, and inverter.
Frequency (or hertz) is directly linked to the motor’s swiftness (RPMs). In other words, the quicker the frequency, the quicker the RPMs proceed. If an application does not require an electric motor to perform at full rate, the VFD can be used to ramp down the frequency and voltage to meet certain requirements of the electrical motor’s load. As the application’s motor quickness requirements modify, the VFD can merely arrive or down the electric motor speed to meet the speed requirement.
The first stage of a Variable Frequency AC Drive, or VFD, is the Converter. The converter is certainly made up of six diodes, which are similar to check valves found in plumbing systems. They allow current to movement 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) can be more positive than B or C stage voltages, after that that diode will open up and invite current to circulation. When B-phase becomes more positive than A-phase, then the B-phase diode will open up and the A-phase diode will close. The same holds true for the 3 diodes on the adverse aspect of the bus. Therefore, we obtain six current “pulses” as each diode opens and closes. That is called a “six-pulse VFD”, which may be the regular configuration for current Adjustable Frequency Drives.
Why don’t we 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 plainly 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 with the addition of 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 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 “around” 650VDC. The real voltage depends on the voltage degree of the AC collection feeding the drive, the amount of voltage unbalance on the power 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 known 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 generally referred to as an “inverter”. It has become common in the industry to make reference to any DC-to-AC converter as an inverter.
When we close one of the top switches in the Variable Speed Drive inverter, that phase of the motor is linked to the positive dc bus and the voltage upon that stage becomes positive. Whenever we close one of the bottom level switches in the converter, that phase is linked to the harmful dc bus and becomes negative. Thus, we are able to make any stage on the electric motor become positive or detrimental at will and will hence 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 have to be operate at full velocity, then you can decrease 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 swiftness of the motor-driven tools to the load requirement. There is no other method of AC electric electric motor control which allows you to do this.
By operating your motors at most efficient swiftness for your application, fewer errors will occur, and therefore, production levels increase, which earns your company higher revenues. On conveyors and belts you eliminate jerks on start-up permitting high through put.
Electric motor systems are responsible for more than 65% of the power consumption in industry today. Optimizing engine control systems by setting up or upgrading to VFDs can reduce energy usage in your facility by as much as 70%. Additionally, the utilization of VFDs improves item quality, and reduces creation costs. Combining energy effectiveness tax incentives, and utility rebates, returns on investment for VFD installations can be as little as six months.