Clause 3 – How to understand the definition of “working voltage”

working votlage: maximum voltage to which the part under consideration is subjected when the appliance is supplied at its rated voltage and operating under normal operation, with controls and switching devices positioned so as to maximize the value
NOTE 1 working voltage takes into account resonant voltages.
NOTE 2 When deducing the working voltage, the effect of transient voltages is ignored.

The rated voltage is generally the supply voltage of the sample under test, however, in the internal circuit of the appliance under normal working condition, there will be some circuits on the voltage is greater or less than the rated voltage. Commonly used general fan with AC asynchronous motor, need to start capacitor, start capacitor voltage on both sides will generally be greater than the rated voltage; or in some step-up transformer secondary circuit will produce higher than the rated voltage of the voltage; Obviously, an appliance can have more than one working voltage. According to the standard, it is sometimes necessary to evaluate and determine whether this part of the circuit (the ” which the part under consideration” in the definition) meets the safety requirements of the standard based on the operating voltage. In this case, we need to consider the maximum voltage that may be generated in the operating circuit, as defined in the standard. According to the definition, in order to get the maximum value of the working voltage, it is necessary for the product to be supplied with the rated voltage and operated under normal working conditions (if the product is labeled with a rated voltage range, it is generally used as the upper limit of the rated voltage range to supply the voltage, such as the rated voltage of 220-240V, that is, 240V power supply), and at the same time, it is necessary to set the controller and the switching device inside the product to supply power with the rated voltage and operate under normal working conditions. power supply and operate under normal operating conditions; the purpose is to ensure that the highest operating voltage can be obtained, the assessment is based on the product is in the harshest operating conditions. In addition, the peak test is not specifically mentioned here, so the working voltage is a RMS value.

The determination of creepage distances in clause 29 is based on the working voltage to determine the creepage distance limit, which then requires the working voltage at certain locations in the product. Clause 13 Electrical Strength Tests, the test voltages applied to the insulated structure are also based on the working voltage.