VFD basics, What is a VFD ? And how does it work ? animation

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Normally how do we control our motors, in the industrial field ?
First option to use a contactor, which will cause high starting torque and current and very fast it will reach the maximum speed.
Other better option is to use a soft starter, Which will reduce the starting torque, and the motor speed will ramp up till reach the full speed, but it will take time more than the contactor.
But in both cases, Just the motor has reached the full speed it will be stuck there untill we turn it off.
But in some applications it's required to adjust the speed during operation, So we need a variable frequency drive.
When we need to start a motor, the power is connected to the circuit breaker input, and the breaker output to be connected to the VFD.
If the motor required to run with the full speed the VFD will transfer the power to the motor with the same frequency, but also the VFD can cut down the motor speed by reducing the output power frequency.
Say to 30 Hertz from 50 hertz, So the motor will slow down,.
Also the VFD is able to change the output speed again and again during the operation.
For better understanding how the power frequency affecting the 3 phase motor speed,.
Back in the late 1800s Nikola Tesla invented the 3 phase AC motor,.
You can imagine the effect if Mr. Tesla didn't invent the AC motor, At least we wouldn't make this video.
In Mr. Tesla design there are two main parts,.
Startor and Rotor.
The stator including the windings ,. A, B and C phase.
The rotor is the second part which is located in the motor center, and it's the part which spins when motor starts, it's also attached to motor shaft, Which will be linked to the driven load.
Now we need to understand how the motor operates.
When the A phase enters the motor,. The electricity flowing causes one set of the winding to be positive and the opposite set to become negative,.
That will create a magnetic field between them,.
If you see the sine wave pattern,. When the sine wave is in the positive half, The winding in this side will be positively charged,. And the other side is negatively charged,.
When the sine wave is in the negative half,. the polarity inside the motor reverses,.
By the effect of these magnetic fields, the rotor will be charged as well,.
If we added the B and C phases,.
When A phase losses the strength,. The B phase will gain strength then will lose the strength later and C phase will gain the strength as well,.
And that will keep the magnetic rotating continuously till motor stopped.
The rotating magnetic field,. will complete one cycle when the A phase starts from Zero, Then being positive for half cycle,. negative for another half cycle then back again to Zero,.
And as well the rotor will try to follow the stator rotating magnetic field,.
Let we imagine that this cycle will be repeated for 50 times in one second,. the rotor will spin in a certain speed,.
If we slow the frequency of these cycles,. to be 30 times per second and we know that the rotor will follow the rotating stator magnetic field,. So the rotor will slow down as well.
What is a VFD?
A Variable Frequency Drive (VFD) is a type of motor controller that drives an electric motor by varying the frequency and voltage supplied to the electric motor.
Other names for a VFD are variable speed drive, adjustable speed drive, adjustable frequency drive, AC drive, microdrive, and inverter.
Frequency (or hertz) is directly related to the motor’s speed.
In other words, the faster the frequency, the faster the speed go.
If an application does not require an electric motor to run at full speed, the VFD can be used to ramp down the frequency and voltage to meet the requirements of the electric motor’s load.
As the application’s motor speed requirements change, the VFD can simply turn up or down the motor speed to meet the speed requirement.
How does a Variable Frequency Drive work?

The first stage of a Variable Frequency AC Drive, or VFD, is the Converter. The converter is comprised of six diodes, which are similar to check valves used in plumbing systems. They allow current to flow in only one direction; the direction shown by the arrow in the diode symbol. For example, whenever A-phase voltage is more positive than B or C phase voltages, then that diode will open and allow current to flow. When B-phase becomes more positive than A-phase, then the B-phase diode will open and A phase diode will close. The same is true for the 3 diodes on the negative side of the bus. Thus, we get six current “pulses” as each diode opens and closes. This is called a “six-pulse VFD”, which is the standard configuration for current Variable Frequency Drives.
The main VFD parts
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