A Variable Frequency Drive (VFD) is a type of electric motor controller that drives a power electric motor by varying the frequency and voltage supplied to the electric powered motor. Other titles for a VFD are adjustable 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). Quite simply, the faster the frequency, the quicker the RPMs go. If an application does not require a power motor to run at full quickness, 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 acceleration requirements modify, the VFD can merely arrive or down the motor speed to meet up the speed requirement.
The first stage of a Variable Frequency AC Drive, or VFD, is the Converter. The converter is usually comprised of six diodes, which act like check valves found in plumbing systems. They allow current to flow in only one direction; the path demonstrated by the arrow in the diode symbol. For example, whenever A-phase voltage (voltage is comparable to pressure in plumbing systems) is more positive than B or C phase voltages, after that that diode will open and allow current to stream. When B-stage turns into more positive than A-phase, then the B-phase diode will open up and the A-stage diode will close. The same holds true for the 3 diodes on the unfavorable aspect of the bus. Therefore, we obtain six current “pulses” as each diode opens and closes. That 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 on a 480V power system. 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 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 operates in a similar style to a reservoir or accumulator in a plumbing system. This capacitor absorbs the ac ripple and delivers a clean dc voltage. The AC ripple on the DC bus is normally significantly less than 3 Volts. Therefore, the voltage on the DC bus turns into “around” 650VDC. The real voltage will depend 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 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 again to ac can be a converter, but to tell apart it from the diode converter, it is usually known as an “inverter”. It is becoming common in the market to make reference to any DC-to-AC converter as an inverter.
Whenever we close one of the top switches in the inverter, that stage of the motor is connected to the positive dc bus and the voltage upon that stage becomes positive. When we close one of the bottom switches in the converter, that phase is connected to the unfavorable dc bus and becomes negative. Thus, we can make any stage on the motor become positive or adverse at will and will hence 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 have to be operate at full swiftness, then you can cut down energy costs by controlling the motor with a variable frequency drive, which is among the benefits of Variable Frequency Drives. VFDs allow you to match the rate of the motor-driven tools to the load requirement. There is no other method of AC electric electric motor Variable Speed Drive control that allows you to do this.
By operating your motors at most efficient velocity for the application, fewer mistakes will occur, and therefore, 
production levels will increase, which earns your business higher revenues. On conveyors and belts you eliminate jerks on start-up allowing high through put.
Electric motor systems are accountable for more than 65% of the energy consumption in industry today. Optimizing motor control systems by setting up or upgrading to VFDs can decrease energy usage in your service 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 investment for VFD installations can be as little as six months.
Your equipment can last longer and can have less downtime because of maintenance when it’s controlled by VFDs ensuring optimal motor application speed. Due to the VFDs ideal control of the motor’s frequency and voltage, the VFD will offer you better security for your engine from problems such as electro thermal overloads, stage security, under voltage, overvoltage, etc.. When you start a load with a VFD you won’t subject the motor or driven load to the “quick shock” of across the series starting, but can start smoothly, therefore eliminating belt, equipment and bearing wear. In addition, it is a great way to lessen and/or eliminate drinking water hammer since we are able to have easy acceleration and deceleration cycles.