Sizing Isolation Contactor Welding Technology （上浆隔离触头焊接技术）.pdfVIP

Sizing Isolation Contactor RULES FOR SIZING ISOLATION CONTACTORS By Jack Farrow, WTC RD Center, February 7, 2001 Copyright, 2001 by WTC FOR WTC RESISTANCE WELDING CONTROLS DISCLAIMER: The purpose of this document is to assist in selecting the proper size isolation contactor for a given welding application. This document does not constitute any recommendation, warranty or obligation on the part of Welding Technology Corporation or any of its employees, representatives or distributors. The user of this information assumes all responsibility for proper use of the information. The information in this document is presented as-is; no warranty of correctness or suitability for any application is given or implied. The calculations in this document have been simplified and are designed for the most common situations. If the application is very unusual, for example a system with large welding transformers above 400 KVA, a system with more than six welding transformers, or a system with a very low welding duty cycle (below 1%), competent engineering help should be sought to size the isolation contactor. ASSUMPTIONS: The process to select the correct size of an isolation contactor consists of two parts. Part 1 calculates the average primary current draw of each welding transformer in the system. Given the average primary current draw of each welding transformer in the system and how they are connected, Part 2 selects the appropriate size isolation contactor. This selection guide assumes the following things: The isolation contactors are rated in amperes by UL general purpose current, which is a continuous-duty current. The isolation contactors are not opened or closed while weld current is flowing. The KVA ratings on the nameplates of the welding transformers are in accordance with the RWMA standards for resistance welding transformers. The power line voltage is between 420 and 5