Switch-on delay
As a restart delay in the is control and automation technology, a combination of several relay or an electronic circuit called a reconnection is prevented before the expiry of a preset time with the aid of.
Executions
The following solutions are available for a restart delay:
1. A programmable logic controller (PLC) opens and closes switching contacts under program control after the last operating time.
2. A combination of different relays ( link programmed control ).
- a) After the last operation, a relay with a switch-off wiper sends a short pulse to a time relay, which, with a switch-off delay , opens one or more normally open contacts for a preset time . If the timing relay does not have an NC contact, the signal of the timing relay must be inverted with a third relay.
- b) the NC an off-delay time relay controls a second relay, which in turn bridged by a normally open the normally closed contact of the first relay, in self-holding is and also after the last operation keeps open via the control input B1 to the contact of the time relay for a preset time. Switching on again is not possible during this time. The prerequisite for this version is that the response time of the second relay is significantly shorter than that of the timing relay.
- c) Version b is extended by a third relay in order to use the switching delay of a mechanical relay. The third relay delays the impulse to control input B1 in order to extend the closing time of the break contact 15-16.
Applications
In many control electronics cases , it is required that after the last operation of a drive or a system, a certain time must elapse before it can be restarted. This applies in particular to electric motors with reversing contactor circuits . Typical applications for restart delays are e.g. B .:
- Drive motors with heavy starting ,
- Drives with a change of direction of rotation with a longer run-down time after switching off,
- High-speed electric motors or those with a large momentum of the rotating masses,
- Drives for heat pumps, compressors, elevators or hoists,
- The drawing shows an example of a reversing contactor circuit with a restart delay.
For complex control tasks, timing relays and connection-programmed controls are used less today and are mostly replaced by programmable logic controllers. In many simple control tasks, however, the effort involved is disproportionate and can be implemented more easily with relay circuits.
See also
literature
- Gerd Engbarth, Heinrich Hübscher, Jürgen Klaue, Stephan Sausel, Mike Thielert: Electrical engineering orders. 1st edition. Westermann Verlag, 2005, ISBN 3-14-221533-6 .
- Peter Bastian among others: Electrical engineering. 25th edition. Verlag Europa-Lehrmittel, 2006, ISBN 3-8085-3159-2 .
- Klaus Beuth, Wolfgang Schmusch: Basic electronic circuits 3rd 14th edition. Verlag Vogel, Würzburg 2000, ISBN 3-8023-1843-9 .
- Fanal circuit practice. 5th edition. Metzenauer & Jung, Wuppertal 1969, OCLC 1075499596 .