Motor duty cycle
The only representative duty cycle for electric actuator operation
The IEC 60034 standard defines the electric motors' standard duty cycles. According to this standard, S2 duty rating is short time duty: motors using this duty cycle adapt to constant load. Temperature rises fast during the operation and quickly reaches its limit. Motor needs long stop for total cooling between each start.
S4 duty cycle is intermittent duty with starting. Motors using this cycle start with a large output torque. Temperature slowly decreases once operating torque has been reached. Therefore, the motor can be restarted shortly after shutdown.
BERNARD CONTROLS has chosen the S4 duty rating because it is the most representative duty cycle for actuators operations. Indeed, the valve's starting torque is much larger than the operating torque, and any valve frequently starts (even On/Off valves may need frequent starting in case of debug or under some special circumstances). Therefore, S4 is the only representative duty cycle for actuator operation.
On the other hand, BERNARD CONTROLS actuators also feature powerful asynchronous motors with high starting torque to unseat the valve, as well as excellent starting torque/nominal torque ratio.