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1.1.1.      Motor standards

International standard IEC 34-1 defines 8, IEC 60034-1 10, different stampings for different ways to use a motor: S1, S2… S10. These are named as follows:

S1 - Continuous running duty. Stamp: S1.

S2 - Short-time duty. Stamp e.g.: S2 10 min. Thermal equilibrium not reached. De-energised rest to reach the coolant temperature within 2 K.

S3 - Intermittent periodic duty. Stamp e.g.: S3 25%. Identical cycles. The starting current may not significantly affect the temperature rise.

S4 - Intermittent periodic duty with starting. Identical duty cycles, significant starting time, constant load, de-energized at rest. FI = (J_L+J_M)/J_M. Stamp e.g.:

S5 - Intermittent periodic duty with electric braking. This is like S4 but with electric brake.

S6 - Continuous-operation periodic duty. Identical cycles, also the idling power is observed, no time in rest.

S7 - Continuous-operation periodic duty with electric breaking. Like S6 but each cycle includes also electrical breaking. Stamping like in S4.

S8 - Continuous-operation periodic duty with related load/speed changes. Stamping example:

S9 - Duty with non-periodic load and speed variations. The duty includes frequently applied overloads that may greatly exceed the reference load (P_ref is appropriately based on duty type S1).

S10 - Duty with discrete constant loads and speeds. Duty consists of a specific number of discrete values of load (and if applicable, speeds), each for sufficient time to allow the machine to reach thermal equilibrium. The parameter TL expresses the thermal life expectancy of the insulation system as compared to the value of duty type S1. Stamping example:

                      S10: p/Δt = 1,1/0,4; 1/0,3; 0,9/0,2; r/0,1 TL = 0,6

In the Figure 46, there is shown an example of a value plate of a motor. The connection possibilities to the supply are shown in the Figure 47. Notice, that in both connections the voltage over the windings is 400 V and the current through is 3.8 A. The decimal comma is used in the plate and the pictures, instead of decimal point, according to the IEC standard.

Figure 46

Figure 47

The nominal electrical power can be calculated as shown here:

                      P_electric = sqrt(3)VIcosφ = sqrt(3)·400V·6.6A·0.82 = 3750 W.

With the nominal load the efficiency is:

                      η = P_shaft/P_electric = 3000W/3750W = 0.80 = 80 %.

In the USA, NEMA-standards are followed.