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markburnley (Mechanical) (OP)
20 Jun 08 5:41
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 (Electrical)
20 Jun 08 8:14
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 (Electrical)
20 Jun 08 9:00
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 (Electrical)
20 Jun 08 11:33
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
--------------------
"Why not the best?"
Jimmy Carter

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