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RE: Pinging djk. EDGE M8 inrush limiter...

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djk

In Reply to: RE: Pinging djk. EDGE M8 inrush limiter... posted by Cougar on February 19, 2013 at 08:32:16

The CL101 is 0.5Ω 16A, it was used in the Hafler DH500. It was inadequate at protecting the power switch so I changed it to 2.5Ω and added another pole on the relay.
How much does that amplifier draw (on music, not testing)? The current need only be sized for that value. Something around 1.5Ω rated at 8A would probably be about right.
http://www.digikey.com/product-detail/en/MF72-001.3D20/317-1223-ND/1190998
http://www.digikey.com/product-detail/en/MF72-001.3D15/317-1207-ND/1190982
http://www.digikey.com/product-detail/en/CL-21/KC023L-ND/248489
http://www.digikey.com/product-detail/en/MF72-001.5D25/317-1233-ND/1191008
http://www.digikey.com/product-detail/en/MF72-001.5D15/317-1208-ND/1190983

Edits: 02/19/13 02/19/13

Follow Ups:

RE: Pinging djk. EDGE M8 inrush limiter... - Cougar 07:39:04 02/20/13 (8)
hi djk,
sine the amp already has a CL-101 I will just upgrade to a 2.0 Ohm 18A NTC. this should be good enough for the soft start for the extra capacitance I will have now @ 47,000uf/80VDC. I will also be upgrading the power switch to a 20A from 16A.
- What really destroys the switch is arcing more than surge. - Chip647 08:32:06 02/21/13 (7)
  If you have a big enough surge to take out the switch, you would absolutely blow the fuse first. The problem is really arching. Arching happens when you throw a switch that will draw several amps. The inrush limiter will help diminish the arching by lessening the load, but a better solution for saving the switch is to install a 3000 v, 0.01uf ceramic disc capacitor across the switch terminals. This will absolutely prevent arching. The only downside is that there will be a little bit of voltage leaking though the cap, so when you work on it, unplug it.
  The inrush limiter is still important to keep the amp from popping fuses when the switch is thrown. But if you keep having to replace power switches, then the cap is the way to go.
  
  Edits: 02/21/13
  - Are you sure ? - djk 12:32:47 02/21/13 (6)
    I find your advice to be totally wrong.
    
    Most amplifiers have caps across the switch for arc prevention, it doesn't keep them from eating the switch from the turn-on transient.
    
    "you would absolutely blow the fuse first."
    
    Never, ever, (ever) had that problem.
    
    The back-EMF that causes the arcing is from interrupting an inductive load, not establishing it (turning it on).
    - RE: Are you sure ? - Chip647 13:44:37 02/21/13 (5)
      When you are "eating the switch from the turn-on transient" what is your belief as to the cause of the damage to the switch?
      
      If it is simply the non-arching transient current that exceeds the rating of the switch, that is a part specification problem.
      - RE: Are you sure ? - djk 16:47:02 02/21/13 (4)
        
        In Reply to: RE: Are you sure ? posted by Chip647 on February 21, 2013 at 13:44:37
        
        "then the cap is the way to go."
        And your solution of a capacitor is going to help how?
        The 2Ω inrush current limiter should do the trick, your capcitor will not.
        
        Edits: 02/21/13
        
        It suppresses the arching. (nt) - Chip647 07:34:15 02/22/13 (3)
        
        In Reply to: RE: Are you sure ? posted by djk on February 21, 2013 at 16:47:02
        
        When you open the switch, not when you close it ! - djk 12:45:46 02/22/13 (2)
        
        In Reply to: RE: It suppresses the arching. (nt) posted by Chip647 on February 22, 2013 at 07:34:15
        
        When you open the switch, not when you close it !
        
        Most designs already have a cap, and a lot bigger value as well.
        
        There is a spark when you close the switch as well. - Chip647 07:30:20 02/23/13 (1)
        
        In Reply to: RE: When you open the switch, not when you close it ! posted by djk on February 22, 2013 at 12:45:46
        
        Haven't you ever had a wall switch spark on you when you flip on a light switch?
        
        I use the glass Amperite delay/relay switches for some circuits. I can definitely tell you that they spark when thrown unless a cap is across them.
        
        What destroys the switch is the arch welding that happens when the switch is partially open. Reducing the current surge at start-up with a thermistor is helpful, but so is a cap and a properly designed switch. The $0.99 buggers that most manufacturers use are not appropriate.
        
        RE: There is a spark when you close the switch as well. - djk 17:12:47 02/23/13 (0)
        
        In Reply to: RE: There is a spark when you close the switch as well. posted by Chip647 on February 23, 2013 at 07:30:20
        
        I am not aware of a quality amplifier that does not already have an appropriate sized cap across the switch from the factory.

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