Motor turn down - what does it mean?

markburnley · Jun 20, 2008

In a new position at work, and guys around me are talking about motor "turn down".

Would someone please give me a description of what "turn down" means.

Thanks

Mark

KnThrak1982 · Jun 20, 2008

Sure someone else can explain this a bit better than I can but as far as I'm aware, turndown ratio is simply the ratio of the rated speed to the minimum speed at which the motor can handle the rated load.
Therefore a higher turndown ratio implies slower speeds are possible without causing damage. i.e. the speed can be "turned-down" more.

oldfieldguy · Jun 20, 2008

I've heard the term in relation to motors with variable speed capabilities, i.e., variable speed drives, and "turn down" is the minimum speed that the motor will be useful, such as able to spin up the load equipment.

Our motors have a range of 50-105% RPM. At 50%, the centrifugal compressors are spinning but at normal operating pressures they're performing very little compressing.

old field guy

waross · Jun 20, 2008

I have always known the phrase "turn down" to express the ratio of maximum over minimum in regards to a variable quantity.
Example; a gas burner will operate over a range of 250,000 BTU/Hr. to 10,000,000 BTU/Hr. The turn down ratio is 10,000,000/250,000 = 40 or 40:1
Does this explanation fit your context?

Bill
--------------------
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Jimmy Carter

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Motor turn down - what does it mean?

markburnley

Mechanical

KnThrak1982

Electrical

oldfieldguy

Electrical

waross

Electrical

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