Duty cycle

The duty cycle is the maximum permissible operating interval of an electronic component or a machine, after which a rest phase must take place 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 device cannot produce the rated power constantly, but only temporarily. An example of this is an appliance that cannot dissipate the heat loss quickly enough and therefore cannot withstand a constant load without causing damage. Examples of appliances with a duty cycle include welding equipment, electric motors, DC motors, grinders and power relays.

For transformers , the duty cycle ED is the ratio of the switch-on or load time to the operating time. In order to avoid impermissible temperature increases, the maximum cycle time of 10 minutes must not be exceeded (anything above this corresponds to continuous operation).

The duty cycle is calculated as follows:
ED % = operating time : (operating time + operating time) x 100%

The type power at short-term load is calculated as follows:
Type power = rated power x √ED % : 100

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 operation without the influence of start-up on the temperature
S4: Intermittent operation with the influence of start-up on the temperature
S5: Intermittent operation with the influence of start-up and braking on the temperature
S6: Continuous operation with intermittent load
S7: Continuous operation with start-up and braking
S8: Continuous operation with load change