| ??? 12/13/08 15:42 Read: times |
#160897 - fast response time is necessary Responding to: ???'s previous message |
Per Westermark said:
But how can you then get 150V from multiple directions?
You have one (1) 24V power supply? The intention with the crowbar is tht the fuse is on the side where the 150 may arrive. The SCR + TVS (Transient Voltage Suppressor) will react to the overvoltage and short to ground, resulting in an overcurrent that blows the fuse. The 150V will then be disconnected before damaging your 24V PSU. The important thing is that the crowbar must be very fast, so that it shorts before the PSU gets damaged. You can make the crowbar bi-directional by having a fuse on each side, in case you don't know which side that will introduce the high-voltage "attack". But everything on the wrong side of the fuse will of course be unprotected by the crowbar if the 150V power source is capable to continue to feed 150V after the fuse has blown and disconnected the crowbar. So if you have a bus or star with multiple equipment, and the 150V may arrive anywhere on this bus/star, then you must have one crowbar for each connected equipment. This will give quite a number of fuses to replace. If this represents a problem, there are alternatives to the fuses. Only the driving output side , fast response time will be required to save the Transil in the first place thats a worry http://www.8052.com/forumchat/read/160895 . As for alternative to fuse PTC or circuit breakers are too slow to save the devices do you have any other option. I think even a 5000W rated Transil wont hold short circuit currents at 150VDC any longer than the Crowbar to perform its slow action . Is it wise to use Transils for this particular application? , as Zener is slower than the Transil. Thanks/ Ap |
| Topic | Author | Date |
| Protecting supply | 01/01/70 00:00 | |
| Of course there are | 01/01/70 00:00 | |
| info | 01/01/70 00:00 | |
| Crowbar | 01/01/70 00:00 | |
| crowbar | 01/01/70 00:00 | |
| Like this | 01/01/70 00:00 | |
| Short-circuit protection | 01/01/70 00:00 | |
| I like Kai's solution better! | 01/01/70 00:00 | |
| that MAY (I emphasize MAY) work | 01/01/70 00:00 | |
| TVS might blow up | 01/01/70 00:00 | |
| SCR survival! | 01/01/70 00:00 | |
| How attack from both directions? | 01/01/70 00:00 | |
| No nothing is removed | 01/01/70 00:00 | |
| Distributed equipment to protect? | 01/01/70 00:00 | |
| fast response time is necessary | 01/01/70 00:00 | |
| Look at an oscilloscope trigger circuit | 01/01/70 00:00 | |
| and... | 01/01/70 00:00 | |
| Mosfet | 01/01/70 00:00 | |
| The other way round | 01/01/70 00:00 | |
| not a Zener | 01/01/70 00:00 | |
| SCRs are slow! | 01/01/70 00:00 | |
| Zeners are slow! | 01/01/70 00:00 | |
| Slow? | 01/01/70 00:00 | |
| Try to convince the mechancis by arguing... | 01/01/70 00:00 | |
| Nice grip... | 01/01/70 00:00 | |
Maybe you can reverse the damage | 01/01/70 00:00 |