Hockey puck SCR anode/cathode?

Discussion in 'General Electronics Chat' started by kenw232, May 24, 2015.

  1. kenw232

    Thread Starter Active Member

    May 18, 2009
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  2. MaxHeadRoom

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    The side with the flange is the anode.
    Normally the gate is closest to the Anode.
    Max.
     
  3. kenw232

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    May 18, 2009
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    So the way I have it labeled is correct then. The top there is the anode, the tab at the bottom is for the cathode..
     
    Last edited: May 24, 2015
  4. MaxHeadRoom

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    No the bottom is the Anode in the pic normally.
    Max.
     
  5. ian field

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    I'm guessing an SCR that big wouldn't be harmed by the voltage from a 12V transformer or the current to light a car indicator bulb.

    A 100R resistor should do for feeding the gate from one end then the other.

    If the bulb lights half-bright before you apply anything to the gate - the SCR has an integral diode.
     
  6. Hypatia's Protege

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    As a side note, please be advised that proper (mechanical) 'clamping' is essential to device operation and integrity -- and not merely for heat-sink efficiency! It seems the construction 'expects' a precise compressive force (should be found in the Specs) --- Indeed many such units test (electrically) open while 'uncompressed'...

    Best regards
    HP
     
  7. kenw232

    Thread Starter Active Member

    May 18, 2009
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    Thats interesting, it won't work unless I physically clamp it down with a screw..? I assume the hole in the center goes right through it then. If anyone knows where to buy custom heat sinks for these To-200AB packages please post. Something like below does not have a hole in the center to bolt it to the SCR so I have no idea how to properly clamp it.
    http://www.digikey.ca/product-search/en?x=4&y=22&lang=en&site=ca&KeyWords=882-200AB
     
  8. Hypatia's Protege

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    It may or may not test OK out of compression, however it will not be reliable...

    I very much doubt it -- I've not encountered a device designed to be clamped via a transfixing fastener...

    Hardware, or 'leads' thereto, should be available from the manufacturer...:)

    Best regards
    HP
     
  9. ian field

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    You'll probably want to start with a significant block of aluminium for the heatsink, tap 2 or 4 lengths of studding to stick up vertically beside/around the puck.

    AFAICR: one firm I worked for fashioned an insulating cross member out of Tuffnol. That of course tightens down to clamp a sheet aluminium top contact.
     
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  10. t_n_k

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    Mar 6, 2009
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    My recollection of the mounting of these devices is that manufacturers also sold mounting clamps with calibrated compression nuts that incorporated a belville washer that "releases" at the correct compressive loading on the device surfaces. Also it was recommended that the number of compression / release cycles be minimised - lest the internal electrical bonding mechanism degraded.
     
    Last edited: May 25, 2015
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  11. Hypatia's Protege

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    As Per the attached datasheet, the recommended pressure is 500 kg --- While it is a simple matter to calculate the requisite torque via consideration of fastener thread pitch, please note that highly effective (e.g. PTFE based) thread lubricant is essential is acceptable accuracy to be achieved...

    Best regards
    HP
     
  12. markdem

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    Jul 31, 2013
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    I am intrigued. Why will this device not work reliably unless it has pressure applied?

    Thanks
     
  13. Hypatia's Protege

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    FWIW said compression is required to establish/maintain internal connection --- I've not researched the rationale behind such design...:confused:

    Best regards
    HP
     
    Last edited: May 26, 2015
  14. kenw232

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    May 18, 2009
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  15. MaxHeadRoom

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    NO, this just need bolting to the chassis or H.S. and normal ring terminals etc used for termination.
    Max.
     
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  16. ian field

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    It seems unlikely that there isn't some form of bonding on the internal junctions, but I'm guessing that there will be some flexing of the mounting plate faces when its correctly torqued down, that would be taken into account in design and manufacture - that tiny bit of flexing has to be there for it to reach its full peak current spec.

    Although I vaguely remember reading that the old "top hat"/stud devices were assembled as a semiconductor pellet soldered to the header, then the shell was seam welded round the flange as another assembly - the terminals that passed through the glass seal made pressure contact with pads on the die.
     
  17. MaxHeadRoom

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    This from Vishay, I could not find anything about clamping H.P. types in any of the IR literature I have.
    Max.
     
  18. Hypatia's Protege

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    FWIW In my own experience new devices (directly sourced from reputable distributors) often test 'open' (~30% incidence) sans a (minimum) compressive force of 50kg - 100kg -- Curious indeed...:confused:

    Best regards
    HP
     
  19. ian field

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    Once I worked for a firm that used those press-fit rectifiers like the ones in car alternators.

    As the firm were a bunch of cheapskates, they had an unskilled lackey pressing them into the heatsink on a pillar drill with the chuck unscrewed just the right amount to clear the solder tag.

    While I was on production test, I rejected quite a few that were visibly damaged (3 dents around the solder lug) - apparently the service dept got more than their share of rectifier jobs.
     
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  20. markdem

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    Jul 31, 2013
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    Hmm. Make one wonder why it would be manufactured in such a way in the first place.
    I too had a look at a range of vendors and can't find any literature that mentions anything, besides the required force\toque, too why it is so.
     
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