Electric motor terminology

[QSIMDO]

Reading about a 1 hp, 3 phase Leeson motor I encountered the term " ...Speed Range 2:1."

What does that refer to please?

[gvasale]

Describe the whole of the label. More information is needed. It could be a 2 speed motor, but...

[QSIMDO]

Here ya' go; http://www.surpluscenter.com/Electri...OR-10-2718.axd

[A.K. Boomer]

would a 1:1 be a 3600 rpm motor?

[Highpower]

"Inverter rated", so maybe it's safe to run at 2 x 60 Hz = 120 Hz = 3600 RPM?

[Royldean]

"ask a question"... they are pretty good about responding to them

[A.K. Boomer]

Where's JT when you finally do have something useful for him to do???

[nc5a]

I believe the speed range 2:1 refers to the turn down ratio of this inverter duty motor. In other words 1800/2 = 900 rpm would be the lowest rpm you should run it.

[MaxHeadRoom]

I would be inclined to see it as double the plate rpm, i.e. 120Hz also.
It comes right after Inverter Rated. Being a 4 pole motor it should be capable of 50Hz x2 .
I would expect a lower rpm than 900rpm capability.
Max.

[J Tiers]

Where's JT when you finally do have something useful for him to do???

Doing useful paying work.....

Inverter rated suggests indeed that it may be a turn-down ratio for full power. I'd have expected a "max speed" for the top end.

that 2:1 does not seem to appear on the nameplate, and it is 1725 rpm, obviously not 1800. You can mouse over the pic to zoom.

[RWO]

Not enough data to make any assumptions. I'm sure the 2:1 speed range rating is for 30-60 Hz operation. "Inverter rated" is silly since virtually any general purpose, NEMA spec motor can run at half speed with rated torque.

RWO

[Forrest Addy]

You have to look at motor specs with a certain amount of understanding. I speculate the "speed range 2 to 1" and "Inverter Rated" refers to the maximum turn-down (ie 900 RPM) for the motor's cooling fan to be effective circulating air over the motor to keep it within max temp ratings at continuous full load service (100% duty cycle) at max environment temperature in still air etc.

Less extreme operating conditions means your safe turn down extends with lowered duty cycle, lowered ambient air temperature, etc. For service in a step pulley drill press for example running a hole saw, 300 motor RPM to get 100 RPM on the drill spindle the motor will run at full load Amps for 30 seconds at a time with intervals of no load to clear chips,apply coolant adjust and re-clamp the work etc. Duty cycle is low and while the motor may warm up there will be little chance of the stator temperature to rise to the point of damaging the insulation.

If you're going to run a circulating fan, compressor, or irrigation pump at full load Amps at half rated motor RPM in a hot environment you better consider motor cooling carefully. In the home shop where manual machine tools are the norm low duty cycle prevails and you can safely (but vigilantly) run induction motors well into overload and far below continuously duty cooling RPM.

If you're cursed with an obsessive personality and cannot rest unless an Arctic blast is directed at your drill press motor reflect and consider: this aint Hollywood. Stuff does not explode into flaming fragments because a rating or red-line is momentarily exceeded. Your nose will tell you when the motor is warm long before the smoke billows forth.

[MaxHeadRoom]

There are a few specs that go into a Vector rated motor, an example is the Baldor vector rated motors with balance and bearings that are good for up to 6000rpm.

http://www.baldor.com/mvc/DownloadCenter/Files/BR400

Max.

[Mark Rand]

For run of the mill induction motors there's usually no difference in construction between the rotor of a 2 pole and 4 pole motor. So the rotor of an 1800 rpm motor will be quite happy at 3600 rpm. This isn't guaranteed for large motors or for 6 or 8 pole motors etc.

[JRouche]

typo...