Mystery voltage

Discussion in 'General Electronics Chat' started by mpeng1, Nov 1, 2013.

  1. mpeng1

    Thread Starter New Member

    Nov 1, 2013
    11
    0
    Hello all out there!!! I am new to this forum stuff so please don’t beat up on me too bad for my mistakes. I am a mechanical design engineer by nature but I get myself tied up into electrical stuff from time to time and some of it just beats me up. I decided to join one of these forum sites in hopes to get help here and there.

    And now for my headache,
    There are quite a number of circuits in the machine I am working with so it may be hard for me to tell you all about the circuits at this point so let me ask a question in general terms and take it from there.

    There is a hand full of indicator lights on the control panel of this machine and they are 250 volt 1/3 watt lights. We can turn on a power switch to a device that has nothing to do with any of the indicator lights but some of the lights will turn on but be very dim. There is around 40vac showing up on the poles of the lights. They do light up a little so I know that I am not just seeing this ghost voltage thing that I here about.

    Can anyone give me some ideals as to the types of things that could be creating and letting this partial voltage pass thru to the lights?

    Some of the machines devices include;
    Solid state relays, thermal power breakers, bi-metal disc thermostats, resistance heating elements, and items used to start and run an ac motor for a pump.

    Thank you all
     
  2. MrChips

    Moderator

    Oct 2, 2009
    12,452
    3,371
    Is this causing a problem or an indication of a fault?

    Or is it designed to operate in this fashion?

    Incandescent lamps are known burn out at higher rates when they are turned on and off very frequently. One way of extending the lifetime of a lamp is to run a low current through the bulb in order to preheat the bulb when they are supposed to be in the off state.
     
    R!f@@, absf, elec_mech and 1 other person like this.
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,571
    2,381
    Hopefully you have the schematics for the machine?
    If so, analyzing them may point to the cause?
    If you could at least post the relevant section and the power supply origin, it would help.
    I assume that the second device is incorporated into the same machine as the lights that dim, are they powered from the same source?
    Max.
     
    anhnha likes this.
  4. mpeng1

    Thread Starter New Member

    Nov 1, 2013
    11
    0
    Sorry for not putting a lot of info on the post about this. I know that the more info given produces the beat results but I’m not sure just how much info that someone should post at one time on these forums.

    The attachment is the entire electrical schematic for this machine but it does not show the detailed info about each of the components within the circuits.

    Let me try to better describe what the problem is.
    The machine has 1 main power input location that goes into 2 main power switches. Each main power switch supplies power into 2 terminal block groups. Each terminal block group takes care of the power going to and from its own group of components.

    Let’s say that there are no switches in the on position except for the 2 large breakers that are in the terminal block groups. If I flip on the secondary main power switch nothing happens and all of the devices are off because no other switches have been turned on yet. If I flip off the big breaker in the secondary terminal block group, the grid heating light (GHL) starts getting around 40 volts and barely lights up and it should not be doing this.

    This is just one example of what is going on. The same thing happens with the other lights depending on just what is switched on, off, or un-plugged. In some case I get a small amount of power to light up 3 of the lights at the same time even though none of the items that control the lights are turned on.

    The entire operation of this machine works just as it should. This mystery thing is not causing any problems to how the machine works. I know that I can get lights that will only operate at higher voltages to make this go away but I still feel the need to know why this is happening so I do not end up with a real problem with something else down the road.
     
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,571
    2,381
    It would appear obvious that there is an original wiring error, and the light is obtaining a complete path from another source back-feeding the light?
    It also appears the light is coming back to the top of a separate breaker?
    Although it appears the breakers are drawn 'upside-down'?
    I much prefer ladder type circuit diagrams rather than physical layout type, they are much clearer to trouble shoot. (see example).
    Was this a commercially supplied machine, or a custom build by someone?
    Max.
     
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,571
    2,381
    Looking at the dwg again, it appears the GHL light is across the output of the SSR and therefore in series with the heater, when the heater SSR is off, this is the reason it glows as it is getting a source through the Grid HTR.
    But it also would not light when the SSR was on?
    On the surface it appears that GHL is sourced wrong?
    Max.
     
  7. mpeng1

    Thread Starter New Member

    Nov 1, 2013
    11
    0
    Max, I’m sorry for the format of the prints. In the 26 years that I have been engineering I have found myself having to make custom prints for all of the companies that I have worked for so the shop workers can understand how to put things together without me being right there with them. The word “ON” that you see on the breakers is the window on them that says on/off when the breaker switch is worked. I had to put it on the print so the shop would install the breakers in the right orientation on the din rail.

    GHL (L2) side is coming from the coil post #3 of the ssr and GHL (L3) is indeed in series with the (L3) side of the grid heater and the (L2) side of the grid heater comes from the top of the breaker in that terminal group. With that breaker turned off how is power getting thru to make the GHL glow? Is the circuit thru to the GHL not broken with the breaker off?
     
  8. #12

    Expert

    Nov 30, 2010
    16,355
    6,852
    Up to a point.

    Necessary information includes, "What is this machine called?"
    Brand, model number, schematic if possible, what it's doing wrong.

    Every time you ask a question, it requires a person with those skills.
    Every additional question weeds out more of the people that could have answered the first question.
    Do not use 500 words when 50 will be sufficient. We don't get paid for reading 500 words only to find out this is not in our skill set.
    Keep it short if you can.
    "Chat" is a place to chew on hypotheticals.
    "Projects" is a place to post things that need you to get your soldering iron heated up.
    Mistakes are allowed. Trying to defend a mistake isn't. Just look at my signature line!:D

    That's a partial answer.
    Partial answers are allowed. Other helpers will supplement the partial answer if they can.

    Right now, I can't make heads or tails out of your schematic. It's not your fault. I just can't seem to get it in gear today.
     
  9. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,571
    2,381
    Acording to the drawing, something does not jive with the supply to the grid HTR and GHL, the way it is drawn both sides are fed from the same phase or live L2?
    Is that a link terminal on the RH side of the main breaker that supplies term 3 of the SSR?
    Is the SSR numbering for a standard block type Opto22? 1&2 power side 3 & 4 switching side?
    BTW, if you are responsible for laying out prints for custom machinery etc, I suggest you obtain a copy of NFPA79, Electrical Standards for Industrial Machinery. Not very expensive. There was a PDF copy floating around at one time.
    Max.
     
    Last edited: Nov 1, 2013
  10. mpeng1

    Thread Starter New Member

    Nov 1, 2013
    11
    0
    I just noticed that page 3 of the temporary print that I made up so we could talk about this shows some L1 notations. Please ignore the L1’s that you see on the sheet, all items on sheet 3 are L2 & L3 only. “sorry”

    Ssr #3 coil is L2 power from tb and from there to the L2 side of the GHL.
    Ssr #4 coil is L3 power from the temp controller when it closes to send power out.
    L3 power feeds into ssr #1 and moves to #2 when ssr is on.
    L3 side of the GHL is live after the ssr turns on.
    L3 side of the grid heater is live after the ssr turns on.
    L2 side of the grid heater is live as long as the L2 breaker is on.
    Terminal block set up is as follows:
    Left side of the solid black bar you see are L3 terminal blocks that are bridged together.
    Right side of the solid black bar is the L2 breaker and a L2 terminal block that are bridged.
     
  11. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,571
    2,381
    You need to specify exactly which is the control side and the output side of the SSR, if this is a common style, then two terminals will be the isolated control, the other pair for the load?
    Unfortunately the Dwg on page 3 really explains little at all, it is what I call a basic termination diagram.
    But at the moment it appears that GHL is across two terminals of the SSR and I think this is where the problem stems from?
    Max.
     
    Last edited: Nov 2, 2013
  12. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,571
    2,381
    Can you post the part number of the SSR that is used?
    Max.
     
  13. mpeng1

    Thread Starter New Member

    Nov 1, 2013
    11
    0
    i will not be back on line until late monday. at that time i will post new stuff.
     
Loading...