Why We Use Variable Frequency Drive

Variable Frequency Drive is a common device in electrical work. I am responsible for several motors with different machinery in my factory and almost 65% of motor having own Inverter and 5% of the motor are having share Inverter that means one Inverter can control two motors at the same time.

Now come to the point, “Why we use Inverter or VFD?” In this post, I am going to discuss all about it. So let’s go.

Why We Use Variable Frequency Drive?

Inverter or VFD or AC Drive normally used to control load speed. Let’s consider you have a conveyer belt that needs to operate with two speeds. If you want to rotate it for 10 meters per minute and after an interval 5 meter per minute. Now how do you control the speed of the conveyer belt? For this occasion, you must use the Inverter / VFD / AC Drive to control the speed of the motor to control the conveyer belt.

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Let’s go for another example of using an inverter. A motor can lift a maximum weight of 20kg and now you want it to lift a maximum weight of 10kg and if there is 11kg weight then your motor will stop automatically by overloaded. So making any program for any motor is very simple when you use an Inverter / VFD / AC Drive to control your motor.

You just need to reduce the torque capacities by programming from Inverter and motor will operate automatically. So your demand can change by your required sector and logic.

If we use an Inverter / VFD / AC Drive to control our motor then famous Star-Delta Connection doesn’t need to be used. First of all, let’s discuss why we use star delta connection for a motor?

Suppose you have a big motor and it starts with a lot of start-up torque. For this reason, motor needs huge Ampere during its starting time. In this case, it impacts on over-power protection system during the motor start running.

Just think, if your power consumption goes up too high and then suddenly decreases then your power supply system will affect badly as well as the other loads and the device will also face some trouble and it just for only one motor.

Ok if the main power supply is coming from a generator then the situation can be more dangerous. For this reason, we follow a simple system to get rid of this problem and it’s called Star Two Delta Connection. But Star and Delta do not control the speed of motor and Star connection take less current than Delta connection.

For this reason for a big load we use Star connection for a couple of second like 3 to 10 or maybe more depending on our demand to start it slowly with less current and when the motor gets enough rotation then we change it to Delta connection for further operation.

Now for this operation, if we use Inverter / VFD / AC Drive then Star-to-Delta Connection does not require. Just a simple program called Accelerator Time and Deceleration Time setting will set the starting and stop delay time for a motor to reduce taking more current.

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Another thing is that if we use an Inverter / VFD / AC Drive to control our motor then we don’t need to use Soft Starter. First of all, let’s find out why we use Soft Starter and how can we replace Soft Starter by an Inverter.

By the name of Soft Starter, we can understand there is something that will start softly. And if it is a large motor then it will start softly and when the motor starts it will not cause harmful effects on the power system. So Soft Starter is responsible to start a motor slowly by programming.

Now you can say an Inverter / VFD / AC Drive works by the same principle. Yes Inverters / VFD / AC Drives have some differences from the soft starter. Normally a place where we don’t need to control a motor when it running at full speed with the full load then we can use a Soft Starter.

But Inverter / VFD / AC Drive use where we need to control motor speed all time during its operation. In my factory, we have some machine with ABB ACS880 Inverter and it controls the machine main motor by a pattern with different speed.

ABB ACS880 Inverter
ABB ACS880 Inverter

Related: What is a Programmable Logic Controller (PLC) With Application?

Now if you find this post useful then please share with your friends. Thanks!

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