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Electric motor duty cycle

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JonFive

Mechanical
Apr 27, 2012
1
I have a motor rated for an S2-10 duty cycle. I understand that its a "short time duty" and have read the IEC's definition so i understand the principle behind the rating and what its trying to accomplish....

My question is if the operating time is 10min how long is the whole cycle? and is there a standard to rests between time in operation?
 
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IEC 60034-1 states:
4.2.2 Duty type S2 – Short-time duty
"Operation at constant load for a given time, less than that required to reach thermal
equilibrium, followed by a time de-energized and at rest of sufficient duration to re-establish
machine temperatures within 2 K of the coolant temperature,[ see Figure 2.]"

That means one has to wait until the motor temperature reaches the ambient temperature +/-2dgr.K[or C].
That depends on cooling motor thermal constant and on maximum reached temperature in the heating process.
These approximated relations could explain the situation:
Tmot-Tambiant=(Tmax-Tambiant)*(e^(-t/Kc)) Kc=cooling constant
Tmot-Tambiant=(Tmax-Tambiant)*(1-e^(-t/Kh)) Kh=heating constant
If Tmot-Tambiant=2 then t=Kc*ln((Tmax-Tambiant)/2)
The Manufacturer has to declare the duty as S2 followed by an indication of the duration of the duty.
Let's say the duration is 60 min then 10 min will be active and 60-10=50 will be duration of the cooling process.
 
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