The term duty cycle refers to the maximum permissible operating interval of an electronic component or a machine, after which a rest period must be observed in order not to damage the machine or the component. The operating modes are defined in DIN VDE 0530-1. A duty cycle is always specified if the electronic component or the device cannot produce the rated power constantly, but only temporarily. An example of this is a device which cannot dissipate the heat loss quickly enough and thus cannot withstand a constant load without causing damage. Examples of devices with a duty cycle include welding equipment, electric motors, DC motors, grinding machines or power relays.
The duty cycle for transformers is the ratio of the switch-on or load time to the cycle time. To avoid inadmissible temperature increases, the maximum cycle time of 10 minutes must not be exceeded (anything above this corresponds to continuous operation)..
According to the standard, a distinction is made between the following operating modes:
S1: continuous operation, constant load
S2: Short-term operation, constant load
S3: Intermittent duty without influence of start-up on temperature
S4: Intermittent duty with influence of start-up on temperature
S5: Intermittent duty with influence of start-up and beraking on temperature
S6: Intermittent duty with intermittent load
S7: Continuous operation with start-up and breaking
S8: Continuous operation with load change