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Do-It-Yourself (DIY) Question & Answer Forum
3ph DOL star/delta (auto changeover)
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<blockquote data-quote="kme" data-source="post: 9076" data-attributes="member: 113"><p>Hi guys.</p><p></p><p>Just been to look at a job on the starter to a large compressor.</p><p></p><p>It "wouldn`t start"!! Likely to be the starter then! :B </p><p></p><p>So went and freed the stuck contactor, and off it goes. HOWEVER.......</p><p></p><p>We`ve got 6 motor wires - all red - unmarked. 3 of them are not connected to the contactor - appears to have a contactor pole fault (delta).</p><p></p><p>The "start" button doesn`t -switch the local isolator on, contactor 1 fires, then 2 &amp; 3 after a short delay.</p><p></p><p>I understand the process involved, and the general wiring proceedure. My question is:</p><p></p><p>If they want to to repair/replace the starter (which they do),</p><p></p><p>1...Who makes the best/most cost effective solution?</p><p></p><p>2... The three motor wires which are disconnected. How can I determine which is which? Or, if my thinking is correct, does it matter, as, from rusty knowledge, they all get shorted together when the delta contactor fires.</p><p></p><p>DOL box contains: 3 3ph contactors. 1 electronic time delay. 6 motor winding wires (u,v,w,u2,v2,w2 I think???) 4 control wires from compressor. 3 phases supplied (no neutral).</p><p></p><p>Strangely, I didn`t see an overload in there. However there is a small "radial lead" component - varistor or something maybe? Think it may be to do with the time delay. It`s connected between motor contactor L3, and star contactor L1 (at least, that`s where, from memory, i THINK it was!)</p><p></p><p>Cheers guys. The 3 ph side of it isn`t a problem; I`ve never had dealings with an auto-changeover before. Plus these un-connected motor wires are spooking me a little, in case I`m wrong about the correct connections.</p><p></p><p>KME</p></blockquote><p></p>
[QUOTE="kme, post: 9076, member: 113"] Hi guys. Just been to look at a job on the starter to a large compressor. It "wouldn`t start"!! Likely to be the starter then! :B So went and freed the stuck contactor, and off it goes. HOWEVER....... We`ve got 6 motor wires - all red - unmarked. 3 of them are not connected to the contactor - appears to have a contactor pole fault (delta). The "start" button doesn`t -switch the local isolator on, contactor 1 fires, then 2 & 3 after a short delay. I understand the process involved, and the general wiring proceedure. My question is: If they want to to repair/replace the starter (which they do), 1...Who makes the best/most cost effective solution? 2... The three motor wires which are disconnected. How can I determine which is which? Or, if my thinking is correct, does it matter, as, from rusty knowledge, they all get shorted together when the delta contactor fires. DOL box contains: 3 3ph contactors. 1 electronic time delay. 6 motor winding wires (u,v,w,u2,v2,w2 I think???) 4 control wires from compressor. 3 phases supplied (no neutral). Strangely, I didn`t see an overload in there. However there is a small "radial lead" component - varistor or something maybe? Think it may be to do with the time delay. It`s connected between motor contactor L3, and star contactor L1 (at least, that`s where, from memory, i THINK it was!) Cheers guys. The 3 ph side of it isn`t a problem; I`ve never had dealings with an auto-changeover before. Plus these un-connected motor wires are spooking me a little, in case I`m wrong about the correct connections. KME [/QUOTE]
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3ph DOL star/delta (auto changeover)
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