Variable Speed Drives (Inverters)
Fitting a variable speed drive to an existing motor can help to reduce its energy consumption considerably. With an average payback of approximately 2 years, it is easy to understand why they have become so popular in recent times.
Motor Cost
Over the entire operating life of a motor, 5% of its cost will have been spent on its initial purchase, 5% on its maintenance and 90%
on its energy requirement.
The Cube Law The power of a motor traces its speed by the cube law. This exponential relationship means that a speed reduction of just 20% will reduce the power consumption by 50%.
Improved Control
Inverters are not just an effective way of saving energy; they also provide improved control and reliability of the system to which
they are fitted. There are no mechanical parts to wear out or cause frictional losses and the variable frequency can be fine tuned
more effectively than using dampers and actuators.
Start-up with VSDs
On start-up the motor is wound up to speed steadily, this reduces wear on the motor, pulleys, belts and the associated fan/pump.
As a result there is a cost saving to be made by reducing the amount of maintenance required and increasing the operating life of the
equipment. Additionally when the motor starts, the amount of current required is much less than that required by other starting
methods including star-delta and even soft-starting.
Overview of VSD Technology
Enhanced Capital Allowances
Inverter manufacturer’s including ABB, Trend, Siemens etc have their inverters listed on the Carbon Trust’s Energy Technology Product List (ETPL) and as such are liable for enhanced capital allowances. With this scheme the cost of the product and any direct costs related to its installation and transportation can be used to reduce the amount of corporation tax that a company pays. In basic terms, if a company pays 30% corporation tax, then for every £100 spent on an approved product, £30 can be claimed back from the government.
