{"id":55,"date":"2020-01-13T13:38:29","date_gmt":"2020-01-13T18:38:29","guid":{"rendered":"https:\/\/opentextbc.ca\/basicmotorcontrol\/chapter\/zero-speed-switch\/"},"modified":"2023-03-02T11:54:18","modified_gmt":"2023-03-02T16:54:18","slug":"zero-speed-switch","status":"publish","type":"chapter","link":"https:\/\/opentextbc.ca\/basicmotorcontrol\/chapter\/zero-speed-switch\/","title":{"raw":"Zero-Speed Switch","rendered":"Zero-Speed Switch"},"content":{"raw":"Click play on the following audio player to listen along as you read this section.\r\n\r\nhttps:\/\/media.bccampus.ca\/id\/0_37it4e8a?width=608&amp;height=80&amp;playerId=23449753\r\n\r\nA [pb_glossary id=\"232\"]zero-speed switch[\/pb_glossary], also called a plugging switch, is commonly connected, either directly or via a belt, to the shaft of the motor or the equipment that it drives and consists of a set of [pb_glossary id=\"237\"]contacts[\/pb_glossary] that are activated by centrifugal force from the rotation of the shaft mechanism. The sets of contacts can come as either [pb_glossary id=\"229\"]normally open[\/pb_glossary] or [pb_glossary id=\"230\"]normally closed[\/pb_glossary]. Each set will change their state when subjected to shaft rotation.\r\n\r\nSeveral symbols are used for zero-speed switch contacts, and the curved arrow represents the rotation of the motor to either open or close the contacts depending on their normal state.\r\n\r\nThe threshold of when these contacts open or close can be easily adjusted with a screw through the switch housing.\r\n\r\nSince the slightest rotation can activate the switch contacts and introduce a hazard, some plugging switches are equipped with a special solenoid coil called a [pb_glossary id=\"240\"]lockout relay[\/pb_glossary]. The lockout relay incorporates a mechanism to disable the contacts until the motor itself has been energized.\r\n\r\nZero-speed switches are used in circuits to provide either [pb_glossary id=\"226\"]plugging[\/pb_glossary] action (momentarily reversing a motor to stop it) or [pb_glossary id=\"231\"]anti-plugging[\/pb_glossary]\u00a0 action (preventing the reversal of a motor until it has come to a rest).\r\n\r\nAs a rule, a zero-speed switch with normally open contacts will provide plugging action, and a zero-speed switch with normally closed contacts will provide anti-plugging action.\r\n\r\n[caption id=\"attachment_33\" align=\"aligncenter\" width=\"300\"]<img class=\"wp-image-33 size-medium\" src=\"https:\/\/opentextbc.ca\/accessibilitytoolkit\/wp-content\/uploads\/sites\/314\/2020\/01\/Untitled-7-2-e1580150749589-300x171.png\" alt=\"\" width=\"300\" height=\"171\" \/> Zero-speed switch contacts.[\/caption]","rendered":"<p>Click play on the following audio player to listen along as you read this section.<\/p>\n<p><iframe loading=\"lazy\" id=\"kaltura_player\" title=\"Zero-speed switch\" src=\"https:\/\/api.ca.kaltura.com\/p\/148\/sp\/14800\/embedIframeJs\/uiconf_id\/23449753\/partner_id\/148?iframeembed=true&#38;playerId=kaltura_player&#38;entry_id=0_37it4e8a&#38;flashvars[leadWithHTML5]=true&#38;flashvars[streamerType]=auto&#38;flashvars[localizationCode]=en&#38;flashvars[sideBarContainer.plugin]=true&#38;flashvars[sideBarContainer.position]=left&#38;flashvars[sideBarContainer.clickToClose]=true&#38;flashvars[chapters.plugin]=true&#38;flashvars[chapters.layout]=vertical&#38;flashvars[chapters.thumbnailRotator]=false&#38;flashvars[streamSelector.plugin]=true&#38;flashvars[EmbedPlayer.SpinnerTarget]=videoHolder&#38;flashvars[dualScreen.plugin]=true&#38;flashvars[Kaltura.addCrossoriginToIframe]=true&#38;wid=0_lul7mpfq\" width=\"608\" height=\"80\" allowfullscreen=\"allowfullscreen\" sandbox=\"allow-downloads allow-forms allow-same-origin allow-scripts allow-top-navigation allow-pointer-lock allow-popups allow-modals allow-orientation-lock allow-popups-to-escape-sandbox allow-presentation allow-top-navigation-by-user-activation\" frameborder=\"0\"><\/iframe><\/p>\n<p>A <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_55_232\">zero-speed switch<\/a>, also called a plugging switch, is commonly connected, either directly or via a belt, to the shaft of the motor or the equipment that it drives and consists of a set of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_55_237\">contacts<\/a> that are activated by centrifugal force from the rotation of the shaft mechanism. The sets of contacts can come as either <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_55_229\">normally open<\/a> or <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_55_230\">normally closed<\/a>. Each set will change their state when subjected to shaft rotation.<\/p>\n<p>Several symbols are used for zero-speed switch contacts, and the curved arrow represents the rotation of the motor to either open or close the contacts depending on their normal state.<\/p>\n<p>The threshold of when these contacts open or close can be easily adjusted with a screw through the switch housing.<\/p>\n<p>Since the slightest rotation can activate the switch contacts and introduce a hazard, some plugging switches are equipped with a special solenoid coil called a <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_55_240\">lockout relay<\/a>. The lockout relay incorporates a mechanism to disable the contacts until the motor itself has been energized.<\/p>\n<p>Zero-speed switches are used in circuits to provide either <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_55_226\">plugging<\/a> action (momentarily reversing a motor to stop it) or <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_55_231\">anti-plugging<\/a>\u00a0 action (preventing the reversal of a motor until it has come to a rest).<\/p>\n<p>As a rule, a zero-speed switch with normally open contacts will provide plugging action, and a zero-speed switch with normally closed contacts will provide anti-plugging action.<\/p>\n<figure id=\"attachment_33\" aria-describedby=\"caption-attachment-33\" style=\"width: 300px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-33 size-medium\" src=\"https:\/\/opentextbc.ca\/accessibilitytoolkit\/wp-content\/uploads\/sites\/314\/2020\/01\/Untitled-7-2-e1580150749589-300x171.png\" alt=\"\" width=\"300\" height=\"171\" srcset=\"https:\/\/opentextbc.ca\/basicmotorcontrol\/wp-content\/uploads\/sites\/314\/2020\/01\/Untitled-7-2-e1580150749589-300x171.png 300w, https:\/\/opentextbc.ca\/basicmotorcontrol\/wp-content\/uploads\/sites\/314\/2020\/01\/Untitled-7-2-e1580150749589-1024x585.png 1024w, https:\/\/opentextbc.ca\/basicmotorcontrol\/wp-content\/uploads\/sites\/314\/2020\/01\/Untitled-7-2-e1580150749589-768x439.png 768w, https:\/\/opentextbc.ca\/basicmotorcontrol\/wp-content\/uploads\/sites\/314\/2020\/01\/Untitled-7-2-e1580150749589-1536x878.png 1536w, https:\/\/opentextbc.ca\/basicmotorcontrol\/wp-content\/uploads\/sites\/314\/2020\/01\/Untitled-7-2-e1580150749589-65x37.png 65w, https:\/\/opentextbc.ca\/basicmotorcontrol\/wp-content\/uploads\/sites\/314\/2020\/01\/Untitled-7-2-e1580150749589-225x129.png 225w, https:\/\/opentextbc.ca\/basicmotorcontrol\/wp-content\/uploads\/sites\/314\/2020\/01\/Untitled-7-2-e1580150749589-350x200.png 350w, https:\/\/opentextbc.ca\/basicmotorcontrol\/wp-content\/uploads\/sites\/314\/2020\/01\/Untitled-7-2-e1580150749589.png 1941w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><figcaption id=\"caption-attachment-33\" class=\"wp-caption-text\">Zero-speed switch contacts.<\/figcaption><\/figure>\n<div class=\"glossary\"><span class=\"screen-reader-text\" id=\"definition\">definition<\/span><template id=\"term_55_232\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_55_232\"><div tabindex=\"-1\"><p>A switch that is activated by centrifugal forces and is attached either directly or via a belt to the shaft of the motor.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_55_237\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_55_237\"><div tabindex=\"-1\"><p>The conducting part of a switch that makes or breaks a circuit.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_55_229\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_55_229\"><div tabindex=\"-1\"><p>A contact that under normal conditions does not have continuity through it. When the contact changes its state it permits the flow of current by closing its contacts. Can be associated with pushbuttons, pilot devices or magnetic contactors.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_55_230\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_55_230\"><div tabindex=\"-1\"><p>A contact that under normal conditions has continuity through it. When the contact changes its state it interrupts the flow of current by opening its contacts. Can be associated with pushbuttons, pilot devices or magnetic contactors.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_55_240\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_55_240\"><div tabindex=\"-1\"><p>A special solenoid coil included in a plugging switch assembly that disables the contacts until the motor itself has been energized.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_55_226\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_55_226\"><div tabindex=\"-1\"><p>When a motor is spinning in one direction and is stopped and suddenly re-energized in the opposite direction before the shaft of the motor has time to come to a complete stop.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_55_231\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_55_231\"><div tabindex=\"-1\"><p>A circuit that is not designed to suddenly stop or reverse a motor until the shaft has come to a rest.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><\/div>","protected":false},"author":90,"menu_order":3,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-55","chapter","type-chapter","status-publish","hentry"],"part":38,"_links":{"self":[{"href":"https:\/\/opentextbc.ca\/basicmotorcontrol\/wp-json\/pressbooks\/v2\/chapters\/55","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/opentextbc.ca\/basicmotorcontrol\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/opentextbc.ca\/basicmotorcontrol\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/opentextbc.ca\/basicmotorcontrol\/wp-json\/wp\/v2\/users\/90"}],"version-history":[{"count":3,"href":"https:\/\/opentextbc.ca\/basicmotorcontrol\/wp-json\/pressbooks\/v2\/chapters\/55\/revisions"}],"predecessor-version":[{"id":438,"href":"https:\/\/opentextbc.ca\/basicmotorcontrol\/wp-json\/pressbooks\/v2\/chapters\/55\/revisions\/438"}],"part":[{"href":"https:\/\/opentextbc.ca\/basicmotorcontrol\/wp-json\/pressbooks\/v2\/parts\/38"}],"metadata":[{"href":"https:\/\/opentextbc.ca\/basicmotorcontrol\/wp-json\/pressbooks\/v2\/chapters\/55\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/opentextbc.ca\/basicmotorcontrol\/wp-json\/wp\/v2\/media?parent=55"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/opentextbc.ca\/basicmotorcontrol\/wp-json\/pressbooks\/v2\/chapter-type?post=55"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/opentextbc.ca\/basicmotorcontrol\/wp-json\/wp\/v2\/contributor?post=55"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/opentextbc.ca\/basicmotorcontrol\/wp-json\/wp\/v2\/license?post=55"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}