The nominal mode of operation describes the basic loading of an electrical machine. It is defined in international standard IEC 60034-1. It helps provide an initial assessment of whether a component (motor, hydraulic power pack) is suitable for a particular application.
If no nominal mode of operation is indicated on the machine’s type plate, it is designed for continuous operation with a constant load. The other nominal modes of operation require additional information, such as the switching cycles per hour and the duty cycle.
The following modes of operation are also used for hydraulic power packs:
Code | Description | Development of power (torque) and temperature |
S1 | Continuous operation with constant load Load duration is sufficient to achieve thermal equilibrium. | |
S2 | Short period operation The thermal equilibrium is not reached during the load period. In the pause between the load cycles, the duration to allow the motor to reach its cold state again is adequate. | |
S3 | Periodic intermittent operation (also: standby mode) A sequence of identical cycles, each of which contains a constant load and a pause. The starting current is insignificant for heating. | |
S6 | Continuous periodic operation (also: continuous operation with intermittent load) Periodic operation with a succession of equivalent cycles, each of which contains a constant load and a no-load time. No pause occurs. |