Motor rating on dust extract

[Ian Barley]

I was recently successful on a dust extractor system. This is an old system which used a 415V 3phase motor. My shop only has 230V single phase so I am gonna change the motor (Its at least twenty years old and as big as a house anyway!).

The existing motor is 2HP and I can easy fit a modern 3HP in the same space. My question is whether there is any point?

Is there any advantage to be had in more power when a 2HP will be quite capable of spinning the impeller at full revs. Logic suggests that once a motor is running at full revs the effort required is effectively only what is needed to overcome friction and air resistance. By uprating the motor will I simply be running the same performance at a higher electrical cost?

Any thoughts most welcome.

(PS As a refuge from the Pond - The temperature in the creek seems to be pretty much the same - congrats to all responsible for getting this place going!)

[Doug Edwards]

First let me say that if the motor is sized larger than the power requirement, it should work fine. But, every motor has a "sweet spot" in its operating curve where it is most efficient. This is usually somewhere around 80% of full speed. You could save dollars (sorry, pounds, or is it euros? :) ) on the power usage using the smaller motor.