{"id":95,"date":"2020-01-13T14:50:33","date_gmt":"2020-01-13T19:50:33","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/basicmotorcontrol\/?post_type=chapter&p=95"},"modified":"2020-08-14T17:24:55","modified_gmt":"2020-08-14T21:24:55","slug":"anti-plugging-with-timers","status":"publish","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/basicmotorcontrol\/chapter\/anti-plugging-with-timers\/","title":{"raw":"Anti-Plugging with Timers","rendered":"Anti-Plugging with Timers"},"content":{"raw":"A forward\/reverse circuit can use two off-delay timers to provide anti-plugging action in an [pb_glossary id=\"746\"]anti-plugging circuit<\/strong>[\/pb_glossary].\r\n\r\n\"\"This circuit utilizes two off-delay coils to prevent the forward and reverse coils from being energized until ten seconds after the stop button has been pressed. This will give the shaft of the motor time to wind down to a halt and provide an anti-plugging feature for the circuit. To achieve this, the normal [pb_glossary id=\"796\"]control circuit<\/strong>[\/pb_glossary] for a reversing magnetic starter is modified slightly by connecting an off-delay timer in [pb_glossary id=\"852\"]parallel<\/strong>[\/pb_glossary] with each of the contactor coils.\r\n\r\nSimilar to how the normally closed [pb_glossary id=\"868\"]electrical interlocks<\/strong>[\/pb_glossary] are connected in the circuit, the normally closed timed to close (NCTC) contacts of the timer connected in parallel with the forward coil are connected in [pb_glossary id=\"977\"]series<\/strong>[\/pb_glossary] with the reverse motor starter, and vice versa.\r\n\r\nIf, while the motor is not energized, the forward [pb_glossary id=\"762\"]pushbutton<\/strong>[\/pb_glossary] is closed, TD1 and the forward starter will energize, and the motor will begin to spin in the forward direction.\r\n\r\nIf, while the motor is not energized, the reverse pushbutton is closed, TD2 and the reverse starter will energize, and the motor will begin to spin in the reverse direction.\r\n\r\nIf the motor is energized in the forward direction, the circuit arrangement ensures that for ten seconds after the stop button has been pressed, the motor cannot be sent in the reverse direction as the timed contacts will remain open. Nothing however prevents the motor from being sent in the forward direction again, as the timed contacts for TD2 remain closed.\r\n\r\nIf the motor is sent in the reverse direction, then stopped, TD2 will ensure that the operator must wait ten seconds before the motor can be sent in the forward direction.\r\n\r\nUnder normal operation, this circuit will provide [pb_glossary id=\"705\"]low-voltage protection (LVP)<\/strong>[\/pb_glossary], and the motor will run in either direction until either the stop button is pressed, or an [pb_glossary id=\"690\"]overload<\/strong>[\/pb_glossary] occurs.","rendered":"

A forward\/reverse circuit can use two off-delay timers to provide anti-plugging action in an anti-plugging circuit<\/strong><\/a>.<\/p>\n

\"\"This circuit utilizes two off-delay coils to prevent the forward and reverse coils from being energized until ten seconds after the stop button has been pressed. This will give the shaft of the motor time to wind down to a halt and provide an anti-plugging feature for the circuit. To achieve this, the normal control circuit<\/strong><\/a> for a reversing magnetic starter is modified slightly by connecting an off-delay timer in parallel<\/strong><\/a> with each of the contactor coils.<\/p>\n

Similar to how the normally closed electrical interlocks<\/strong><\/a> are connected in the circuit, the normally closed timed to close (NCTC) contacts of the timer connected in parallel with the forward coil are connected in series<\/strong><\/a> with the reverse motor starter, and vice versa.<\/p>\n

If, while the motor is not energized, the forward pushbutton<\/strong><\/a> is closed, TD1 and the forward starter will energize, and the motor will begin to spin in the forward direction.<\/p>\n

If, while the motor is not energized, the reverse pushbutton is closed, TD2 and the reverse starter will energize, and the motor will begin to spin in the reverse direction.<\/p>\n

If the motor is energized in the forward direction, the circuit arrangement ensures that for ten seconds after the stop button has been pressed, the motor cannot be sent in the reverse direction as the timed contacts will remain open. Nothing however prevents the motor from being sent in the forward direction again, as the timed contacts for TD2 remain closed.<\/p>\n

If the motor is sent in the reverse direction, then stopped, TD2 will ensure that the operator must wait ten seconds before the motor can be sent in the forward direction.<\/p>\n

Under normal operation, this circuit will provide low-voltage protection (LVP)<\/strong><\/a>, and the motor will run in either direction until either the stop button is pressed, or an overload<\/strong><\/a> occurs.<\/p>\n

definition<\/span>