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  1. S

    Volumetric doser controller without opto-isolator on dry contact input

    I think then it's not commercial one. Sometimes they may mark components differently to make them unrecognisable in order to avoid unauthorized repairs.
  2. S

    Volumetric doser controller without opto-isolator on dry contact input

    Turns out it's a L6388ED not L638SED. I think ic manufacturer have made a mistake used ''S'' instead of ''8''.
  3. S

    Volumetric doser controller without opto-isolator on dry contact input

    Unfortunately mosfet driver ic with unknown part number (L638SED E920 or 6K374, google can't find anything) is compromised as well, so this board is rubbish now.
  4. S

    Volumetric doser controller without opto-isolator on dry contact input

    Thanks for answer. I will replace damaged components tomorrow and then see what happens. Sometimes it works successfully. I guess it's not worth for the manufacturer to use opto-isolator if there is only one input.
  5. S

    Volumetric doser controller without opto-isolator on dry contact input

    Bipolar stepper motor H-bridge MOSFET output transistor burned out together with 100nF ceramic capacitor (in parallel between earth and +24V rail) and resettable PPTC fuse after someone decided to apply 110 AC voltage on dry contact input terminals. They said everything was working for couple of...
  6. S

    Industrial grade connector with safety switch

    I had no other choice but to attach a magnet to a locking lever of a Harting/Epic male socket and a magnetic switch on a female plug with a control wire in a separate conduit. As soon as you try to open it motor stops and there is enough time until it's safe to unplug it. Only thing is it might...
  7. S

    Industrial grade connector with safety switch

    Is there anything in BS 7671 about safely disconnecting the motor from the VFD if there is connector in the load side? I don't know if Toshiba vf-s11 is protected against it cause in the manual there isn't anything about it. Nowadays we have a fly-back diode across each transistor in the VFD as...
  8. S

    What do they not teach you at college?

    Thanks, very legitimate and sound words. Properly trained graduate can do any job fast and according to IEC 60364. BS 7671 https://s-media-cache-ak0.pinimg.com/236x/07/fc/5d/07fc5dca38e8801470d7d63d7037ef8e.jpg
  9. S

    What do they not teach you at college?

    Another thing they don't teach is when employer fires you just because you are trying to get things done the right way and to the highest quality. Employers always wan't speed over quality.
  10. S

    A good example why not to use a Twist connector!

    In the past all domestic aluminium conductors in junction-boxes were welded together. Now we use ultrasonic friction welders for that purpose. Only welded or soldered connections are reliable enough.
  11. S

    What do they not teach you at college?

    They know that there are always someone more experienced than you out there.
  12. S

    Newbie seeking help regarding contactors please :)

    Have you tried to simply measure the control voltage on each relay or switch and rechecking dc resistance of every coil, look for loose connections and conductors if yes then there might be something really weird going on.
  13. S

    Single & 3-Phase Voltage in The UK

    In our place we have a 245V on L1 and L2 and 255V on L3. That's the reason why motor current on one phase is always way too high. Another thing is control voltages are always higher, instead of 24VAC we have 28VAC or even 30VAC. For 24V contactors with AC coils it shouldn't be a problem cause if...
  14. vfd3.jpg

    vfd3.jpg

    • sysrq
    • Media item
    • Comments: 0
    • Category: Professional Electrician
  15. S

    VFD Volt Drop Question

    Examples of shielded cables recommended by IEC 60034-25
  16. vfdcable2.jpg

    vfdcable2.jpg

    • sysrq
    • Media item
    • Comments: 0
    • Category: Professional Electrician
  17. vfdcable.jpg

    vfdcable.jpg

    • sysrq
    • Media item
    • Comments: 0
    • Category: Professional Electrician
  18. S

    Choosing a SPDT time relay with adjustable transition time

    Is there any way to find a DIN rail mount SPDT time relay with adjustable transition/changeover time. Need to automatically switch between two reversing contactors without mechanical interlock depending on the coast time of a relatively high inertia load. It might be more cost-effective to use...
  19. S

    Stalled motor and volt free contacts on VFD.

    Thanks for answers. I have no other choice but to add some latching relay and utilize terminal 10 sourcing open collector with terminal 1 0V reference.
  20. S

    Stalled motor and volt free contacts on VFD.

    Good guess. Quoting the manual: ''RS485/RS232 Communication Module You can create a network of drives by linking a Master (PC/PLC) to one or more 650 drives fitted with this module. Plug this Communication Module on to the front of the 650 drive, replacing the keypad. It converts signals from...

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