A Variable Frequency Drive (VFD) is a kind of motor controller that drives an electric motor by varying the frequency and voltage supplied to the electric motor. Other titles for a VFD are adjustable speed drive, adjustable velocity drive, adjustable frequency drive, AC drive, microdrive, and inverter.
Frequency (or hertz) is directly related to the motor’s velocity (RPMs). Put simply, the quicker the frequency, the faster the RPMs go. If a credit card applicatoin does not require an electric motor to run at full rate, the VFD can be used to ramp down the frequency and voltage to meet up the requirements of the electric motor’s load. As the application’s motor speed requirements change, the VFD can merely arrive or down the electric motor speed to meet the speed requirement.
The first stage of a Adjustable Frequency AC Drive, or VFD, may be the Converter. The converter is certainly comprised of six diodes, which are similar to check valves found in plumbing systems. They allow current to movement 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 more positive than B or C phase voltages, then that diode will open up and allow current to movement. When B-stage becomes 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 negative part of the bus. Hence, we get six current “pulses” as each diode opens and closes. That is called a “six-pulse VFD”, which may be the standard configuration for current Variable Frequency Drives.
Let us assume that the drive is operating on a 480V power system. The 480V rating is definitely “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 by adding a capacitor. A capacitor works 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. Therefore, the voltage on the DC bus turns into “around” 650VDC. The actual voltage will depend on the voltage level of the AC line 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 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 usually referred to as an “inverter”. It has become 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 phase of the motor is connected to the positive dc bus and the voltage on that stage becomes positive. When we close one of the bottom level switches in the converter, that phase is linked to the bad dc bus and turns into negative. Thus, we are able to make any phase on the electric motor become positive or bad at will and will thus generate any frequency that we want. So, we can make any phase be positive, negative, or zero.
If you have an application that does not need to be run at full swiftness, then you can cut down energy costs by controlling the engine with a adjustable frequency drive, which is among the advantages of Variable Frequency Drives. VFDs allow you to match the velocity of the motor-driven devices to the strain requirement. There is absolutely no other method of AC electric electric motor control which allows you to do this.
By operating your motors at the most efficient acceleration for the application, fewer mistakes will occur, and therefore, production levels 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 more than 65% of the power consumption in industry today. Optimizing electric motor control systems by installing or upgrading to VFDs can reduce energy usage in your facility by as much as 70%. Additionally, the utilization of VFDs improves product quality, and reduces creation costs. Combining energy effectiveness taxes incentives, and utility rebates, returns on purchase for VFD installations is often as little as 6 months.
If you take the time to develop your knowledge of Variable Speed Drive it can verify quite rewarding in the lengthy run.