{"id":112,"date":"2026-09-14T10:00:00","date_gmt":"2026-09-14T06:30:00","guid":{"rendered":"https:\/\/sanatiblog.ir\/blog\/how-to-choose-a-contactor\/"},"modified":"2026-09-14T10:00:00","modified_gmt":"2026-09-14T06:30:00","slug":"how-to-choose-a-contactor","status":"publish","type":"post","link":"https:\/\/sanatiblog.ir\/fa\/blog\/how-to-choose-a-contactor\/","title":{"rendered":"\u06a9\u0646\u062a\u0627\u06a9\u062a\u0648\u0631 \u0645\u0646\u0627\u0633\u0628 \u0645\u0648\u062a\u0648\u0631 \u0631\u0627 \u0686\u0637\u0648\u0631 \u0627\u0646\u062a\u062e\u0627\u0628 \u06a9\u0646\u06cc\u0645\u061f"},"content":{"rendered":"<p>A contactor is a switch that a small control current turns on and off, so a button or a controller can start a big motor. Four things decide which one you need.<\/p>\n<h2>1. The motor&#8217;s power (AC-3)<\/h2>\n<p>Contactors for motors are chosen by their <strong>AC-3<\/strong> rating, often printed in kW. At 400 V three-phase, as a rough guide:<\/p>\n<ul>\n<li>9 A: up to 4 kW<\/li>\n<li>12 A: 5.5 kW<\/li>\n<li>18 A: 7.5 kW<\/li>\n<li>25 A: 11 kW<\/li>\n<li>32 A: 15 kW<\/li>\n<\/ul>\n<p>For heaters (no motor), the <strong>AC-1<\/strong> rating counts, and it is higher: the same contactor can switch more current.<\/p>\n<h2>2. The coil voltage<\/h2>\n<p>The coil must match your control circuit: usually 220 V AC, or 24 V DC in newer panels with a PLC. A wrong coil burns out, or the contactor does not pull in.<\/p>\n<h2>3. Extra (auxiliary) contacts<\/h2>\n<p>Small extra contacts tell the rest of the circuit &#8220;I am on&#8221;: for a hold-in circuit, a lamp, or the PLC. Count how many you need, normally open (NO) and normally closed (NC). You can add a block later if needed.<\/p>\n<h2>4. The overload relay<\/h2>\n<p>The contactor switches; it does not protect the motor. Add a thermal overload relay set to the current on the motor&#8217;s nameplate, or use a motor protection breaker instead.<\/p>\n<p>For star-delta starting you need three contactors and a timer. Tell the seller the motor&#8217;s kW and current, and they will give you a matched set.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u06a9\u06cc\u0644\u0648\u0648\u0627\u062a \u0645\u0648\u062a\u0648\u0631\u060c \u0648\u0644\u062a\u0627\u0698 \u0628\u0648\u0628\u06cc\u0646\u060c \u06a9\u0646\u062a\u0627\u06a9\u062a\u200c\u0647\u0627\u06cc \u06a9\u0645\u06a9\u06cc \u0648 \u0628\u06cc\u200c\u0645\u062a\u0627\u0644.<\/p>\n","protected":false},"author":0,"featured_media":127,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-112","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/sanatiblog.ir\/fa\/wp-json\/wp\/v2\/posts\/112","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/sanatiblog.ir\/fa\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/sanatiblog.ir\/fa\/wp-json\/wp\/v2\/types\/post"}],"replies":[{"embeddable":true,"href":"https:\/\/sanatiblog.ir\/fa\/wp-json\/wp\/v2\/comments?post=112"}],"version-history":[{"count":0,"href":"https:\/\/sanatiblog.ir\/fa\/wp-json\/wp\/v2\/posts\/112\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/sanatiblog.ir\/fa\/wp-json\/wp\/v2\/media\/127"}],"wp:attachment":[{"href":"https:\/\/sanatiblog.ir\/fa\/wp-json\/wp\/v2\/media?parent=112"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/sanatiblog.ir\/fa\/wp-json\/wp\/v2\/categories?post=112"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/sanatiblog.ir\/fa\/wp-json\/wp\/v2\/tags?post=112"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}