| ??? 02/10/06 08:39 Read: times |
#109678 - thankyou Responding to: ???'s previous message |
Andy Neil said:
Use a relay with a 24V AC coil, connected to the transformer output (before the recfifier). Then as soon as the mains goes off, the 24V AC goes off, and the relay disconnects the DC out. You could have a little light connected across the capacitors - that would warn that they still have charge even though the load is off, and would also gently discharge the capacitors! Fantastic, thankyou so much for the solution recommendation, Kia Klaas said:
The very simplest methode would be to have a resistor permanently connected across storage cap I will try this one as well, thanks Kia, what sort of resisitor value are we talking about here??? Kia Klaas said:
How long may the fall down of potential last? Why is a fast fall down needed at all? At the moment it takes around 20 seconds for capacitors to discharge and I would like to do it in max 1 second, the reason I want to do is that I am using a micro PLC unit to control different motors, one of them is AC and one is DC, both motors are switched on using relays, I have emergency stop connected to mains in, so when I disconnect the main in by pressing emergency stop , the AC motor stops as emergency stops cuts the power to motor BUT relay is still connected via PLC which then takes 4 seconds to go dead and in case some one release the emergency stop during those 4 seconds the PLC stays alive and motor starts again, so emergency stop is not really acting like emergecny stop. So I think if I cut the O/P of capacitor as well with emergency stop as you said below then I think it should be OK, Kia Klaas said:
A good methode would be to combine the turn-off of power supply with the turn-off of motor by additional soft- or hardware: When you want to turn-off the power supply, first turn-off the motor. Then there will be no further current flow and the power supply to motor can be disconnected without sparking. Turning-off power supply should turn-off both, (a) mains from primary side of transfomer and (b) connection between storage cap and motor. Use two separate relays for this. Sounds like brilliant solution, Kia Klaas said:
Also, do you already need a soft start, when switching the transformer to mains? I guess so. At the moment I am switching transformer stright from the mains with no additional device, how can I acheive soft start, I guess I have to use soft cap for that ? Am I right? Please suggest. Thank you very much all regards Kaz |
| Topic | Author | Date |
| Discharging capacitors? | 01/01/70 00:00 | |
| sorry I missed that.. | 01/01/70 00:00 | |
| many versions have been implemented | 01/01/70 00:00 | |
| Simplest | 01/01/70 00:00 | |
| Alternatively... | 01/01/70 00:00 | |
| Switch | 01/01/70 00:00 | |
| thankyou | 01/01/70 00:00 | |
| Emergency stop | 01/01/70 00:00 | |
| Soft start | 01/01/70 00:00 | |
| Combine | 01/01/70 00:00 | |
| if it has to be done the right wa | 01/01/70 00:00 | |
| SPS? | 01/01/70 00:00 | |
| if a SPS is a switching power supply - y | 01/01/70 00:00 | |
| resistor value ?? | 01/01/70 00:00 | |
| DIY | 01/01/70 00:00 | |
| Hmm... | 01/01/70 00:00 | |
the crux | 01/01/70 00:00 | |
| check current rating of capacitors ... | 01/01/70 00:00 | |
| search | 01/01/70 00:00 |