A Variable Frequency Drive (VFD) is a kind of engine controller that drives a power engine by varying the frequency and voltage supplied to the electrical motor. Other names for a VFD are variable speed drive, adjustable acceleration drive, adjustable frequency drive, AC drive, microdrive, and inverter.
Frequency (or hertz) is directly linked to the motor’s rate (RPMs). Quite simply, the quicker the frequency, the quicker the RPMs proceed. If an application does not require a power motor to run at full speed, the VFD can be utilized to ramp down the frequency and voltage to meet up the requirements of the electrical motor’s load. As the application’s motor acceleration requirements modify, 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, is the Converter. The converter is certainly comprised of six diodes, which are similar to check valves found in plumbing systems. They allow current to stream in only one direction; the path proven by the arrow in the diode symbol. For instance, whenever A-stage voltage (voltage is similar to pressure in plumbing systems) can be more positive than B or C stage voltages, then that diode will open up and allow current to flow. When B-phase becomes 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 unfavorable aspect of the bus. Therefore, we obtain 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 certainly “rms” or root-mean-squared. The peaks on a 480V program 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 eliminate the AC ripple on the DC bus by adding a capacitor. A Variable Speed Drive capacitor functions in a similar fashion to a reservoir or accumulator in a plumbing program. This capacitor absorbs the ac ripple and provides a even dc voltage. The AC ripple on the DC bus is normally less than 3 Volts. Hence, the voltage on the DC bus becomes “approximately” 650VDC. The real voltage depends on the voltage level of the AC series feeding the drive, the amount of voltage unbalance on the power system, the motor load, the impedance of the energy 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 again to ac is also a converter, but to tell apart it from the diode converter, it is normally 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 among the top switches in the inverter, that stage of the electric motor is connected to the positive dc bus and the voltage on that phase becomes positive. Whenever we close one of the bottom switches in the converter, that phase is connected to the adverse dc bus and turns into negative. Thus, we are able to make any phase on the engine become positive or adverse at will and will hence generate any frequency that we 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 rate, then you can decrease energy costs by controlling the motor with a variable frequency drive, which is one of the benefits of Variable Frequency Drives. VFDs permit you to match the swiftness of the motor-driven apparatus to the strain requirement. There is absolutely no other approach to AC electric motor control that allows you to accomplish this.
By operating your motors at the most efficient acceleration for the application, fewer errors will occur, and thus, production levels will increase, which earns your company higher revenues. On conveyors and belts you get rid of jerks on start-up allowing high through put.
Electric motor systems are responsible for a lot more than 65% of the energy consumption in industry today. Optimizing 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 efficiency taxes incentives, and utility rebates, returns on expenditure for VFD installations can be as little as six months.