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Contactor coil: 50 Hz vs. 60 Hz

Discussion in 'Electronic Equipment' started by DaveC, Aug 29, 2011.

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  1. DaveC

    DaveC Guest

    I may be able to obtain a very small 2-pole 240 vac contactor I need rated
    for 50 Hz only.

    If I install it in N. America, what's the implication? Is the hold-in
    magnetism less than if it were 60 Hz? Just noisy?

    Please don't ask or suggest other sources. This is a very specific device and
    I've not been able to locate other than this.

    Thanks,
    Dave
     
  2. Rich Grise

    Rich Grise Guest

    Plug one into 60 Hz and find out what happens. It will probably work just
    fine. The Mfr only rated it for 50 because they weren't expecting
    international sales.

    Are you allowed to tell us why it has to be such a narrow menu of choices?

    Thanks,
    Rich
     
  3. Yes, the hold-in force will be proportionally less. If the
    coil impedance was due entirely to the inductance, it would
    be 50/60ths of the force. However, part of the current limiting
    is done by the coil resistance, and that won't change so the
    reduction in hold-in force will actually be less than this.

    The pull-in force before the magnetic core is closed also
    depend on the impedance and resistance, but the impedance
    will be lower, and thus the pull-in force will be reduced by
    even less.

    The pull-in force usually has to overcome a faily weak return
    spring. The hold-in force has to overcome a stronger contact
    pressure spring. Providing both these conditions are still met,
    you should be OK. Ideally, you should check that you have a
    reasonable working margin by testing the coil at lower
    voltage. If you don't, then the contactor might fail to
    close properly on minimum supply conditions which could cause
    it to burn out.

    I would not expect it to be more noisy if it closes properly.
    Noise would be an indication that is isn't closing properly.

    Of course, you void all waranties and certifications by
    operating it outside of it's specified ratings. The
    manufacturers advice should be sought, but unless you are
    buying lots of them, they probably won't commit other than
    to say it's at your own risk.
     
  4. As we have very limited information about this device and its usage, I can
    only suggest two possible solutions:
    - The easy one: Just try it out.
    - Build a piece of electronics that converts your 60Hz to 50Hz.
    Dimensions of that electronics depend on the required current.

    petrsu bitbyter
     
  5. On Mon, 29 Aug 2011 08:58:55 +0000 (UTC), the renowned
    <snip>

    A side effect of reduced holding force can be that it is more
    sensitive to opening due to external vibration in the wrong axis (and
    especially so when the input voltage is on the low side). That could
    cause malfunction of whatever it's connected to and premature failure
    of the contactor. This might not be so easy to test without a shaker
    table etc., but it should be considered if the operating conditions
    involve vibration (including vibration from another nearby contactor).


    Best regards,
    Spehro Pefhany
     
  6. Well, high ambient temperature and low input voltage. May not be that
    unusual. I've seen it happen more than once, particularly in
    industrial situations where ambient temperatures can be relatively
    high.

    I even had to wire an autotransformer into a domestic elevator control
    panel because the designer ignored the necessity of allowing for
    voltage drop when the drive motor started, which caused chattering of
    the AC contactor even in a climate-controlled 22°C environment.
    Since the OP didn't describe the environment.. it may or may not be.
    For aircraft work (yes, some is 60Hz) it would be a really good idea
    to check. If it's sitting on a subpanel with the control cabinet
    bolted to the floor rather than to an OBI punch press, not a big deal.

    Best regards,
    Spehro Pefhany
     
  7. David Lesher

    David Lesher Guest

    It will be happy. If it were a 60Hz on 50, it would not be as happy.
     
  8. David Lesher

    David Lesher Guest

    What's the inductance while closed?
     
  9. DaveC

    DaveC Guest

    If instead you meant you would use it on 110v 60Hz, then dont. But you
    No, there are models for both 115 and 230 in both 50 and 60 Hz flavors. Here
    in N. America these are difficult to get so I may have to settle for the 50
    Hz models, ordered from Europe. Hence my query.

    Thanks,
    Dave
     
  10. DaveC

    DaveC Guest

    ..
    It's usually in old (60's & 70's) V-belt driven letterpress type printing
    presses (think "clamshell" press). No vibration at the controls.

    Thanks,
    Dave
     
  11. DaveC

    DaveC Guest

    It will be happy. If it were a 60Hz on 50, it would not be as happy.
    [David Lesher]

    Interesting. Good to know. It's stuff like this I learn here that I wouldn't
    otherwise know.

    Cheers,
    Dave
     
  12. "NT" <> schreef in bericht
    |
    | The relay has a voltage margin of around 50%, the mains supply wont
    | vary more than 10%, so the transformer is of no use.
    |
    |
    |NT
    |

    "The relay has a voltage margin of around 50%" How do you know? FAIK the op
    did not supply this numbers.

    petrus bitbyter
     
  13. David Lesher

    David Lesher Guest

    Well anytime you run transformers {Be they two fixed windings,
    or one fixed and one rotating aka motor, or one fixed &
    one sliding aka solenoid or relay....} on LESS than design
    frequency, worry. Lower frequencies need more iron.

    I'm not sure the slightly less pull-in power will be relevent but
    it's possible.

    If you do pursue the "make DC and use that..." approach; don't forget
    you need to limit the holdin current. One technique is a cap in parallel
    with a resistor.
     
  14. Hasn't anybody read the original question?

    He wants to know if a 50 Hz relay coil will work at 60 Hz.

    Jeff
     
  15. Rich Grise

    Rich Grise Guest

    Yeah. It was answered some days ago.

    Guess you gotta be quick. ;-)

    Cheers!
    Rich
     
  16. Rich Grise

    Rich Grise Guest

    16 henries, but that measurement was made by closing the armature
    manually.

    If there's any real interest I can measure it energized.
    [/QUOTE]
    Well, I guess that depends on what you mean by "real interest" - I'd be
    interested in seeing your experimental results, but that's just because
    I like seeing experimental results. ;-)

    Cheers!
    Rich
     
  17. David Lesher

    David Lesher Guest

    I have.
    And that's my point; if it were the other way, he SHOULD worry.
     
  18. John S

    John S Guest

    Actually, RMS DC voltage is a redundant expression since DC is RMS.
     
  19. DC would be the RMS value. Because, RMS means "This is what the DC
    value would be."

    Jeff
     
  20. Generally, in electronics, "DC component" is defined as the average
    value (say, over a period of a periodic waveform). So a 1V peak sine
    wave sitting on top of 1VDC would have DC component of 1.0V.
    A 1V peak sine wave has a DC component of 0.

    The RMS value is the heating value- a 1 ohm resistor with 1VDC across
    it will dissipate 1W. A 1 ohm resistor with 1.414V peak sine wave
    across it (1 V RMS) will dissipate 1W.

    A 1 ohm resistor powered with a 1V peak sine wave sitting on top of
    1VDC will dissipate a bit more than 1 watt (RMS value is sqrt(3/2) if
    you want to get analytical about it, so about 1.22W).
     
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