Smoke from CT ports

[Tom Korycki January 1, 2021 at 5:02 am Post count: 0]

#56360 Reply |

I bought 4-in-1 AC meter, PN 200123 earlier this year on Amazon, and it worked pretty well. However few months ago I noticed that after 0,5-1h of use the lower-left corner of the LCD display was going completely dark, which then progressed to cover the whole display – after about 3-4h. The equipment is used only occasionally and after rest the display would start fully legible, so it’s obviously not the logic problem. To be clear, the “Power IN” cables are 10ga (6 square mm), fed from 40A SSR.

Today I got equipment ready for another run, but had to shut down immediately, as there was NO display, just the smoke coming from behind the panel. Motor didn’t even “click” on. After taking the panel off and checking connections, I tried again – same effect, this time I saw that the smoke was coming from the CT ports, which are near the problematic corner. I ordered a replacement unit, disconnected the existing one and now everything works.

I initially thought the display was overheating, so I put a forced-air conduit on it, but now it seems overheating was not caused externally but inside the meter itself. I obviously want to avoid repeating the same problem, so here is the question – what could have caused this problem?

[DrokKeymaster January 2, 2021 at 7:09 am Post count: 2971]

#56432 Reply |

Hello Tom Korycki，

May I know more details? For example, what kind of device is connected? The load current and voltage?

Best regards,

DROK

[Tom Korycki January 3, 2021 at 8:19 pm Post count: 0]

#56539 Reply |

Hi,

What was DIRECTLY connected was 80-260V, 0-100A current regulator, non-linear SCR. What was regulated was current to a resistive 5.5kW device (heater) and 500W device (motor) in parallel. Since the regulator  is non-linear, I got the meter to see how much current/power was actually fed to the devices. Both devices are grounded and the source circuit is balanced (no “floating 0”).

When it comes to power, beginning of the cycle I am drawing 25-30A at 200-240V (depending on the utility company mood) for about 17-20 minutes until the process stabilizes, then maintain 15-25A (depending on source voltage, around 3,5kW indicated) for 4-5h, making occasional adjustment to keep steady state.

Half an hour ago I had another one of Your meters delivered, so I hope this is enough information to allow You to recommend how to avoid this problem in the future; I am not going to mount/connect/test until then.

[Tom Korycki January 3, 2021 at 8:44 pm Post count: 0]

#56541 Reply |

I think You should replace SCR above with a Triac. It’s an old Phillips component that still works. It’s a thyristor, anyway… 😉 It’s controlled by a simple adjustable delay (crossing 0 turns gate off, turn back on after delay) circuit. Couldn’t think of a way to make it linear without spending money…

[Tom Korycki January 14, 2021 at 6:38 pm Post count: 0]

#57318 Reply |

Hello, DROK

If you need any more details, just ask. Or tell me I’m on my own. Otherwise I will need to take the old one apart and try to figure out what went wrong with it. Would You like me to do that and report here?

[Tom Korycki January 15, 2021 at 5:35 am Post count: 0]

#57357 Reply |

Alright, then!

Thank You for Your help.

[DrokKeymaster January 15, 2021 at 8:35 am Post count: 2971]

#57368 Reply |

Hello

As we can’t check your case in person. It is hard to find out what wrong it is. If possible, we would like to get more informaton from you.

Best regards.

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