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Service Duty Types

The most common duty types are described in this paragraph and a method to calculate the permissible power rise-up is given. Please contact MGM for different types of duty.

Continuous duty S1

The motor operates with constant load for a period of time sufficient to achieve the thermal equilibrium.

g 3_

Limited length duty S2

The motor operates with constant load for a limited period of time not sufficient to achieve a thermal equilibrium. The remaining period of the cycle is a rest period, during which the motor cools down to the ambient temperature again.

g 3_

Periodic intermittent duty S3



	A,


	tc
	ts	tr

The motors follows a cycle including an operation period with constant load (ts) and a rest period (tr). The synthetic indication of the duty is given by the intermittent percentage ratio related to a period of time, which usually is 60 min. (f.e. 15% - 60 min.).

•100%

Intermittence ratio =

ts + tr

A motor designed for S1 duty but running on S2 or S3 duty can provide a power output higher than the rated one on S1 duty. However, the starting torque remains the same on all duties.

The permissible approximate output power for single speed motors can be calculated as follows:

Power (S2 or S3 duty cycle)=K»Nominal power Where K is a coefficient given by the following diagrams:

1,4

1,3

1,2

1,1

1,0

Duty %

100

Time (min)