Re: Cheaper ???
old trick when you have inductive load. Why? The breaking speed will get twice as much and this is important if you want a short arc time. => long lifetime
A 8 A relay at 230 VAC will do just fine because you will never break a huge current. Normally I think the volume is down when you switch off the amp. => low current
This is true for a certain load and a certain voltage. In your case it will be less or less lifetime. Two contact in parallel will not give twice the current capability. If you want better breaking capacity you should put the contact in seriesdddac said:
old trick when you have inductive load. Why? The breaking speed will get twice as much and this is important if you want a short arc time. => long lifetimeA 8 A relay at 230 VAC will do just fine because you will never break a huge current. Normally I think the volume is down when you switch off the amp. => low current
Hi,
Peranders is talking about break current capability, how much it can stop when opening under heavy load... the circuit induction wants to keep the juice flowing and there's your arc.
It's possibly more relevant since I think it's the arc that will ruin your relay, especially if the contacts weld, otherwise heavy arcing could drastically reduce lifespan. Certain power relays are meant to handle it though.
My guess is that with two sets of contacts opening up simultaneously in series..... you have twice the airgap isolation than you would with just one.
Now if you want to talk about straight DC current handling parallel would be better in that it reduces I^R losses.
I imagine it would also help it handle the arc but wouldnt' be as effective in quenching it as the increased air gap.
Have I assumed all that correctly Peranders?
Doede if you're selected a good relay for the job it should last a loooong time and I wouldn't worry about the arc. If it fails prematurely you know what to do.
Regards,
Chris
Peranders is talking about break current capability, how much it can stop when opening under heavy load... the circuit induction wants to keep the juice flowing and there's your arc.
It's possibly more relevant since I think it's the arc that will ruin your relay, especially if the contacts weld, otherwise heavy arcing could drastically reduce lifespan. Certain power relays are meant to handle it though.
My guess is that with two sets of contacts opening up simultaneously in series..... you have twice the airgap isolation than you would with just one.
Now if you want to talk about straight DC current handling parallel would be better in that it reduces I^R losses.
I imagine it would also help it handle the arc but wouldnt' be as effective in quenching it as the increased air gap.
Have I assumed all that correctly Peranders?
Doede if you're selected a good relay for the job it should last a loooong time and I wouldn't worry about the arc. If it fails prematurely you know what to do.
Regards,
Chris
Arcs
Since we are talking softstarts and arcs, you might want to check out mine (similar to the original circ posted in this thread-- works great by the way) here, and the discussion of arcing in this thread.
Implementation of this circuit in my Krell KSA 50 is shown here.
Since we are talking softstarts and arcs, you might want to check out mine (similar to the original circ posted in this thread-- works great by the way) here, and the discussion of arcing in this thread.
Implementation of this circuit in my Krell KSA 50 is shown here.
classd4sure said:
OK, let me ask again and help you a bit
...Why are there sparcs in my circuit over the relay contacts, ruining it?? And I mean in my circuit, not in general switching off an inductive load, I do know how that works ... I see no reason for sparcs in this set up, so want to know why people are concerned on the relay ??
doede
Sorry to mix up things for you. The relay which short circuit the 100 ohms (or whatever) can never get sparks so it's either way how you connect your contacs.dddac said:OK, let me ask again and help you a bit
Why are there sparcs in my circuit over the relay contacts, ruining it??
doede
If the relay really breaks a circuit, then it might be a good idea to have the contacts in series if you use more than 1 poles.
hi doede, thanks for posting your circuit
i just have some questions
1. can i hardwire/soder all the components instead of a PCB?
2. on the schematics you have the R2 as 10k, and on the PCB you have a 50k pot in series to a 1k (very short connection, so i'm not sure if it's really a resistor), can you just verify the right values and connection for R2.
3. what's the specs of 8V2 zener, or do you have an exact part number for this component.
4. i'm in the U.S. so do I have to use the same values for R3 (220E 11W), i might have to series (3) x 75E 11W resistors, is that OK?
thanks a lot,
onixuser
i just have some questions
1. can i hardwire/soder all the components instead of a PCB?
2. on the schematics you have the R2 as 10k, and on the PCB you have a 50k pot in series to a 1k (very short connection, so i'm not sure if it's really a resistor), can you just verify the right values and connection for R2.
3. what's the specs of 8V2 zener, or do you have an exact part number for this component.
4. i'm in the U.S. so do I have to use the same values for R3 (220E 11W), i might have to series (3) x 75E 11W resistors, is that OK?
thanks a lot,
onixuser
onixuser said:
Hi Onixuser,
1. Sure, no problem, just a few parts, so should be no issue
2. Good checking
This was an option to use a trimmer, to be able to adjust the delay to exactly the amount of time what is needed for your Transformer. But when I built it I did not have the trimmer at hand, so used the fixed value of 10k... with the trimmer as on the pcb, you can adjust the delay between 1 and 40 seconds...3. you can use any zener you like, it is very uncritical, even from 5 to 10 Volt will work as well. I had a 500mW type, but 1.3 Watt will work as well....
4. Also the Value of R3 is uncritical.... 1 x 75 Ohm will also work. R3 is only there to dampen the inrushcurrent and with your 120 V, you can actually use a lower value. 1 x 75 is very similar with the 230V situation with 220Ohm....
doede
www.dddac.de
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.