Understanding Variable Frequency Drive

A basic variable frequency drive is a motor controller. You might know it by some other names such as variable speed drive, adjustable frequency drive, AC drive, microdrive, inverter and so on. The purpose of this controller is to drive electric motors by alternating the frequency and voltage that is supplied to the motor. For a motor to gain speed it needs frequency so the faster the frequency, the faster the speed of the motor. If some piece of technology does not need to use the full amount of speed, a basic variable frequency drive can adjust the frequency down to meet the requirement of the motor. If the need for speed changes and varies, you can easily adjust it up or down with a variable frequency drive.

Why you should use a variable frequency drive?

The most important reason is, if there is no need for an application to run at full speed, then why wouldn’t you want to save money and cut energy usage by controlling it with a variable frequency drive. There is no other piece of technology like it and it is the only technology that allows you to match the speed of the load requirement the motor needs. Electric motors are notoriously known in the industry for using excess energy and consuming a lot of power and by using a basic variable frequency drive you can cut down energy usage and savings by a big 70%.

By using a variable frequency drive, you can improve the quality of your product and reduce your energy consumption and your bills. By running any application at the appropriate speed, this leaves less room for error so production levels and quality will all increase. This will also give your equipment longer life so you won’t need to replace parts so often and will save money. Investing in a variable frequency drive will save you power, time, and money.

What are the basic parts that make a basic variable frequency drive?

A converter is made with six diodes, which are designed check valves that you see in plumbing systems if you are familiar with that. These diodes allow the current to flow in one direction and you will know which way the current is going by the arrow in the diode symbol. The way these diodes work is when an A-phase voltage becomes more positive than a B or C phase voltage, then that diode opens and allows the current to flow through it. If a B-phase becomes more positive than the A-phase, it will automatically open the B-phase and the A-phase will close. This creates six pulses as each of these open and close accordingly, this is known as a six pulse variable frequency drive which is the stock standard average amount.

The next part of the variable frequency drive you should know about is the capacitor. You will need one of these any time a ripple appears, and it works similar to a reservoir like in a plumbing system. The aim of the capacitor is to absorb any ripple from the AC and deliver a smooth DC voltage. The voltage itself is all dependent on a lot of factors like the level of the AC line that is feeding the drive, the motor load, the impedance of the power system, and any filters or drives that have been installed.

Another key part of the variable frequency drive is the diode bridge converter and its purpose is to convert AC to DC. There is also another converter which does the exact opposite by converting DC back to AC. This can get a bit confusing for most people so to be able to know the difference between the diode converter and the second converter, people will usually call it an inverter. It has become common slang and knowledge to refer to anything that converts DC to AC as an inverter.

Of course, there are many other parts and pieces that make this technology run smoothly and function efficiently but these are the basic parts we should all know about.