2.22 SCHALTGERÄTE Wissenswertes von A-Z Know How from A - Z Under Voltage Release The MERZ UVR-Switches with undervoltage release are available for a power range from 32A - 63A. The undervoltage release switch (UVR) is an electromechanical device which automatically shuts down when the supply voltage falls below a certain value. In such case the handle moves back to the OFFposition. The switch has been designed to open its contacts (release-free) even though the handle is eventually blocked. The undervoltage release is required in many countries especially for machines with rotating tools. Utilisation categories Utilisation categories describe the application of switching devices, referring to load limit values set by the normatives. Differentiation is made between utilisation categories for „AC“ and „DC“. MERZ switchgear are applicable for AC and 3-phase current and designed and tested to the strictest AC categories AC3, AC22 and AC23. As a result they are suitable as well for other „AC“ categories. Code letter „A“ and „B“ placed after the utilisation category refers to the used testing cycle within the respective test. „A“ in general names the more demanding test cycle as the switch has to survive more switching cycles. (DIN VDE 0660 Part 100) See table on page 2.25
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