A Variable Frequency Drive (VFD) is a type of engine controller that drives a power motor by varying the frequency and voltage supplied to the electrical motor. Other brands for a VFD are adjustable speed drive, adjustable swiftness drive, adjustable frequency drive, AC drive, microdrive, and inverter.
Frequency (or hertz) is directly related to the motor’s rate (RPMs). Quite simply, the faster the frequency, the quicker the RPMs go. If an application does not require an electric motor to perform at full speed, the VFD can be used to ramp down the frequency and voltage to meet the requirements of the electrical motor’s load. As the application’s motor rate requirements alter, the VFD can simply arrive or down the electric motor speed to meet the speed requirement.
The first stage of a Variable Frequency AC Drive, or VFD, may be the Converter. The converter is usually comprised of six diodes, which act like check valves found in plumbing systems. They allow current to movement in only one direction; the direction demonstrated by the arrow in the diode symbol. For instance, whenever A-stage voltage (voltage is similar to pressure in plumbing systems) is more positive than B or C phase voltages, then that diode will open and invite current to circulation. 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 holds true for the 3 diodes on the negative aspect of the bus. Hence, we get six current “pulses” as each diode opens and closes. This is known as a “six-pulse VFD”, which is the regular configuration for current Adjustable Frequency Drives.
Let us assume that the drive is operating on 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 has 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 with the addition of a capacitor. A capacitor functions in a similar style to a reservoir or accumulator in a plumbing program. This capacitor absorbs the ac ripple and provides a easy dc voltage. The AC ripple on the DC bus is typically significantly less than 3 Volts. Thus, the voltage on the DC bus becomes “approximately” 650VDC. The real voltage depends on the voltage degree of the AC range feeding the drive, the level 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 Variable Speed Drive converts AC-to-DC, may also be just referred to 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 normally known as an “inverter”. It is becoming common in the industry to refer to any DC-to-AC converter as an inverter.
Whenever we close one of the top switches in the inverter, that phase of the electric motor is connected to the positive dc bus and the voltage upon that phase 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 phase on the electric motor become positive or negative at will and can thus 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 need to be run 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 gear to the strain requirement. There is absolutely no other approach to AC electric electric motor control which allows you to do this.
By operating your motors at most efficient quickness for your application, fewer errors will occur, and therefore, production levels will increase, which earns your firm higher revenues. On conveyors and belts you remove jerks on start-up enabling high through put.
Electric motor systems are accountable for more than 65% of the power consumption in industry today. Optimizing electric motor control systems by setting up or upgrading to VFDs can reduce energy intake in your service by as much as 70%. Additionally, the utilization of VFDs improves product quality, and reduces creation costs. Combining energy performance taxes incentives, and utility rebates, returns on purchase for VFD installations can be as little as 6 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 optimum control of the motor’s frequency and voltage, the VFD will offer better safety for your electric motor from problems such as for example electro thermal overloads, phase safety, under voltage, overvoltage, etc.. When you start a load with a VFD you won’t subject the motor or driven load to the “instant shock” of over the line starting, but can start smoothly, thereby eliminating belt, gear and bearing wear. In addition, it is an excellent way to lessen and/or eliminate water hammer since we are able to have simple acceleration and deceleration cycles.