2.11. Galvanic isolation (PELV)PELV offers protection by way of extra low voltage. Protection against electric shock is ensuredwhen the electrical supply is of the PELV type and the installation is made as described in local/national regulations on PELV supplies.All control terminals and relay terminals 01-03/04-06 comply with PELV (Protective Extra LowVoltage) (Does not apply to 525-600 V units and at grounded Delta leg above 300 V).Galvanic (ensured) isolation is obtained by fulfilling requirements for higher isolation and by pro-viding the relevant creapage/clearance distances. These requirements are described in the EN61800-5-1 standard.The components that make up the electrical isolation, as described below, also comply with therequirements for higher isolation and the relevant test as described in EN 61800-5-1.The PELV galvanic isolation can be shown in six locations (see illustration):In order to maintain PELV all connections made to the control terminals must be PELV, e.g. ther-mistor must be reinforced/double insulated.1. Power supply (SMPS) incl. signal iso-lation of UDC, indicating the inter-mediate current voltage.2. Gate drive that runs the IGBTs (trig-ger transformers/opto-couplers).3. Current transducers.4. Opto-coupler, brake module.5. Internal inrush, RFI, and tempera-ture measurement circuits.6. Custom relays. Illustration 2.2: Galvanic isolationThe functional galvanic isolation (a and b on drawing) is for the 24 V back-up option and for theRS 485 standard bus interface.2. Introduction to VLT HVAC Drive VLT® HVAC Drive Design Guide44 MG.11.B2.02 - VLT® is a registered Danfoss trademark2
