Here, we need to add that SELV has regulations on voltage values. The voltage specified here is the effective value of the voltage. Usually, the peak value of the voltage is higher than the effective value, and the voltage limit specified in clause 8.1.4 is the requirement for the peak value. We will explain its test requirements in detail in clause 8.1.4. Note 2 of first paragraph in Clause 3 give sentence “NOTE 2 When the terms “voltage” and “current” are used, they are r.m.s. values, unless otherwise specified.”
As shown in the figure below, the transformer has three plastic brackets placed vertically into the disc to separate the primary and secondary windings (the primary and secondary windings are wrapped with blue plastic tape on the outside), and the primary and secondary windings are physically isolated.
As shown in the figure below, the transformer has yellow tape wrapped around the primary and secondary windings in the middle. We need to pay special attention to the creepage distance of the black bracket between the two windings to see if it can meet the creepage distance requirements for reinforced insulation. If not, the transformer cannot be judged as a safety isolating transformer.
We will explain the structure of the safety isolating transformer in detail in the next post.
functional insulation as well as other insulation exists on circuit boards. Typically, the surface environment of a circuit board is determined to be either Pollution degree 3 or pollution degree 2.If the circuit board is mounted in an electrical box and sealed with a solid sealant, the sealing will look as follows: What should be…
8.1.5 Live parts of built-in appliances, fixed appliances, and appliances delivered in separate units shall be protected by at least basic insulation before installation or assembly. Compliance is checked by inspection and the test in 8.1.1.Why is this requirement in place? I believe there are three types of hazards that require protection. The first is…
built-in appliance: fixed appliance intended to be installed in a cabinet, in a prepared recess in a wall or in a similar location. Here, because the appliance must be installed in a reserved position (usually a cubic space with only one side open), it is a fixed installation and can be regarded as a fixed…
