VSD Motor Power, Speed & Torque – How and Why

We came across a situation recently on site where an induction motor being driven by a VSD at a reduced speed had the operators asking "Why is the motor running at the rated current but not at the rated power?"
It was actually a very good question and one that we thought we would share with you all.

First of all there are a few things to remember about a motor;

The most basic method of control for an induction motor on a VSD is the Volts per Hertz (V/Hz) method, also known as open-loop or scalar control. This is where the VSD controls the motor speed by maintaining a constant ratio between motor voltage and frequency, as the frequency of the motor is reduced so is the voltage by the same ratio to maintain a constant magnetic flux.

If we have a look at the motor power formula, we see that the speed of a motor (shown as rpm) directly effects the power of a motor;

We have kicked it off finally, our first post, but we can promise there will be many more to come!

We just added the blogging page to our website and we have brainstormed some fantastic topics in the automation industry we would love to discuss. We want to use this space to share ideas, invoke some thought and hopefully pass on the knowledge we have gained (and continue to gain) within the automation industry.

We welcome your feedback so please feel free to let us know your thoughts.
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How was 2015? All we can really say is WOW! What a year it has been! Another year has gone by, and like a lot of people do around this time of year, we look back on what we have achieved as well as looking forward to where we are going in the future. 2015 saw us kick off this exciting adventure and it has been just that, exciting! There have been numerous challenges which is to be expected when starting any new business, work was slow to start with but fortunately through some hard work and Lady Luck we were fortunate enough to have picked up some wonderful clients.
 
Moving forward into 2016, we have quite a bit of work ahead of us which we are looking forward to. There are some exciting opportunities we want to pursue and we are keen to grow the website through our blogging and industry news pages.
 
All the team at Automated Electrics would like to wish you a very Merry Christmas, and a safe and prosperous New Year. Enjoy your time with family and friends because at the end of the day that is what life is about!
 
See you all in 2016!