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Advantages of Inverter Drives

What are the advantages of using an Inverter Drives?

1) Speed Control

Inverter Drives, or Variable Frequency Drive's (VFD's) are able to control the speed of motors according to an input command into the drive. This could be a fixed set speed entered through the drive's keypad, a command communicated through an industrial field bus network such as Profibus DP or a reference signal input directly into the drive's input terminals. Changing the speed ensures the process is optimised both in terms of performance and energy consumption. For example if a motor was connected to a fan and the flow of air needed to be reduced, without an Inverter Drive attached to the motor the only way to reduce the flow of air is to introduce a mechanical flow regulator. By doing so the air flow reduces but the speed of the motor doesn't reduce and the power required does not significantly change. See the diagram below;

Using a mechanical damper to control airflow

If an Inverter Drive is now connected to the motor, the speed of the motor can be reduced to regulate the air flow and the power requirement is also reduced. See the diagram below;

Reduced power requirements using an inverter drive


2) Slow start and slow stop (soft start)

The intelligence of the drive means that different acceleration (and deceleration) profiles can be programmed. Selecting a less aggressive start / stop profile can greatly reduce the stress on the mechanical components of the drive line ensuring a more reliable and long life system. It also may be very important to the success of the process to which the motor is attached. For example, assume the motor was attached to a conveyor belt with bottles standing on it, if the conveyor belt accelerated quickly all the bottles might fall over!

No motor speed control.....

Starting without an inverter can be a very bumpy start   

With motor speed control provided by an inverter drive......

 A soft start with an inverter


3) No speed reducer mechanics required

Fixed speed motors often require speed reduction mechanics to achieve the correct operating speed. These can take the form of gearboxes or belts and pulleys. This creates more cost and more maintenance requirements. The variable speed nature of the inverter drive can eliminate the need for these mechanical interfaces.

No need for mechanical reducers such as pulleys or gearboxes.

4) Reduction in total power requirements

Given that the inverter drive has the ability to operate at an optimum power consumption it follows that the overall power requirements of a factory will be reduced.

Overall power requirements are reduced

5) Motor rotational direction can be changed easily

The direction of rotation of the motor can only be changed by re-wiring the supply to the motor when the motor is wired directly to the supply. However, by using an Inverter Drive the direction of rotation is simply set by using the digital keypad.

Its simple to change direction


Diagrams reproduced by kind permission of Yaskawa Electric.

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What is an “inverter”?

AC Inverters are devices for controlling motor speed by converting a DC voltage generated from your connected power supply to a varying frequency AC voltage which can control the speed of the connected motor. The development of semiconductor technology and the processing power of modern microprocessors have enhanced AC inverter drive performance significantly. When applied to industrial and environmental applications, they have improved productivity, reduced energy needs and made a huge contribution to the development of the motor control industry. They  have also brought about a substantial change to our lives. For example, airflow from air-conditioners, speed of elevators, pumps and fans can all be regulated by changing motor speed.  By regulating the speed, energy consumption is reduced which contributes to energy conservation.

Not sure that it is an Inverter you need? Inverters are called by different names and so it can be confusing, but essentially if you are looking for electronics to control the speed of an AC motor then it is likely that you are looking for an Inverter which can also be known as a Variable Frequency Drive (VFD), Variable Speed Drive (VSD), AC Drive, AC inverter drive, Frequency Converter or AC motor speed controller.

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