{"id":173,"date":"2020-01-13T14:49:48","date_gmt":"2020-01-13T19:49:48","guid":{"rendered":"https:\/\/opentextbc.ca\/basicmotorcontrol\/chapter\/sequence-control-off-delay\/"},"modified":"2022-07-13T16:57:04","modified_gmt":"2022-07-13T20:57:04","slug":"sequence-control-off-delay","status":"publish","type":"chapter","link":"https:\/\/opentextbc.ca\/basicmotorcontrol\/chapter\/sequence-control-off-delay\/","title":{"raw":"Sequence Control: Off-Delay","rendered":"Sequence Control: Off-Delay"},"content":{"raw":"[caption id=\"attachment_172\" align=\"aligncenter\" width=\"1024\"]\"\" Definite sequence control off-delay[\/caption]\r\n\r\nThe above circuit shows a standard [pb_glossary id=\"271\"]three-wire circuit[\/pb_glossary] for a single-motor starter M1. In [pb_glossary id=\"268\"]parallel[\/pb_glossary] with M1 is a [pb_glossary id=\"258\"]time-delay relay (TR)[\/pb_glossary] who\u2019s normally open, timed to open (NOTO) contacts identify it as an off-delay timer. These timed contacts are in [pb_glossary id=\"269\"]series[\/pb_glossary] with motor starter M2.\r\n\r\nThe above switching arrangement will allow two motors to be controlled from a single [pb_glossary id=\"235\"]pushbutton[\/pb_glossary] station. If the start button is pressed both motors M1 and M2 will start instantly. This is because the [pb_glossary id=\"229\"]normally open contacts[\/pb_glossary] associated with the off-delay coil will change their state instantly when the coil is energized.\r\n\r\nOnce both motor starters are engaged, the motors will continue to run until the stop button is pressed. Once pressed, the M1 contactor and the off-delay timer will be de-energized, and their contacts will revert to their original state.\r\n\r\nFor the motor starter,<\/strong> this will happen instantly, but the timed contacts associated with the timer coil will have a delay of five seconds before they open, during which time motor M2 will continue to run. It is important to note that even though the timer coil has been disconnected from its source of power, it still performs its timing function. It does not need external energy to delay its contacts, that energy is stored in the timer, usually as compressed air or spring tension.\r\n\r\nIf an [pb_glossary id=\"208\"]overload[\/pb_glossary] occurs on motor M2, only that motor will stop, but if motor M1 develops an overload and its [pb_glossary id=\"241\"]OLR contacts[\/pb_glossary] open, then the coil will de-energize and its 2-3 holding contact will open, disconnecting the timer coil from the source of supply. Once the off-delay coil is de-energized, its contacts will delay for five seconds, then revert to their original state, so motor M2 will continue to run for five seconds after motor M1 has stopped due to an overload.\r\n\r\nIf more than two motors are to be sequenced in this fashion, we would simply scale up this switching arrangement by connecting additional timer relays in parallel with each motor starter so that each motor stops one after the other in the prescribed sequence.\r\n\r\nhttps:\/\/media.bccampus.ca\/id\/0_ym97nboy?width=608&height=402&playerId=23449753","rendered":"
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Definite sequence control off-delay<\/figcaption><\/figure>\n

The above circuit shows a standard three-wire circuit<\/a> for a single-motor starter M1. In parallel<\/a> with M1 is a time-delay relay (TR)<\/a> who\u2019s normally open, timed to open (NOTO) contacts identify it as an off-delay timer. These timed contacts are in series<\/a> with motor starter M2.<\/p>\n

The above switching arrangement will allow two motors to be controlled from a single pushbutton<\/a> station. If the start button is pressed both motors M1 and M2 will start instantly. This is because the normally open contacts<\/a> associated with the off-delay coil will change their state instantly when the coil is energized.<\/p>\n

Once both motor starters are engaged, the motors will continue to run until the stop button is pressed. Once pressed, the M1 contactor and the off-delay timer will be de-energized, and their contacts will revert to their original state.<\/p>\n

For the motor starter,<\/strong> this will happen instantly, but the timed contacts associated with the timer coil will have a delay of five seconds before they open, during which time motor M2 will continue to run. It is important to note that even though the timer coil has been disconnected from its source of power, it still performs its timing function. It does not need external energy to delay its contacts, that energy is stored in the timer, usually as compressed air or spring tension.<\/p>\n

If an overload<\/a> occurs on motor M2, only that motor will stop, but if motor M1 develops an overload and its OLR contacts<\/a> open, then the coil will de-energize and its 2-3 holding contact will open, disconnecting the timer coil from the source of supply. Once the off-delay coil is de-energized, its contacts will delay for five seconds, then revert to their original state, so motor M2 will continue to run for five seconds after motor M1 has stopped due to an overload.<\/p>\n

If more than two motors are to be sequenced in this fashion, we would simply scale up this switching arrangement by connecting additional timer relays in parallel with each motor starter so that each motor stops one after the other in the prescribed sequence.<\/p>\n

https:\/\/media.bccampus.ca\/id\/0_ym97nboy?width=608&height=402&playerId=23449753<\/p>\n

definition<\/span>