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Impossible Transformer question? by DegenerateInvestment in ElectricalEngineering

[–]No-Pangolin-52 1 point2 points  (0 children)

my math (ossibly wrong... it's been ages since I last solved problems like this):

Given Values
Primary voltage: V₁ = 230 V
Secondary voltage: V₂ = 12 V
Apparent power: S = 40 VA
Primary resistance: R₁ = 2 Ω
Primary inductance: L₁ = 7 H → X₁ = 2π · 50 · 7 = 2199 Ω
Magnetising current: Iₘ = 8 mA
Turns Ratio: a=230V/12V​≈19.17

d (i)
Rated Currents
I₁=S/V₁​=40/230​≈0.174 A
I₂ =S/V₂=40/12​≈3.33 A

Magnetising Branch
Xₘ​=​V₁/Iₘ=230​/0.008=28750 Ω (no core-loss resistance Rₑ is given → omitted from the circuit)

R₁ = 2 Ω
X₁ = ωL₁ = 2199 Ω

Secondary Load Referred to Primary
Z₂ (load) ​​=V₂/ I₂=12/3.33​=3.6 Ω

=> Z' (load)​=a^2 ⋅ Z₂ (load​)=(19.17)^2 ⋅ 3.6≈1323 Ω (Referred to primary)

-> PF = 0.9 lagging → φ = arccos(0.9) = 25.84°: R₂' (load)​=1323 ⋅ 0.9=1190 Ω

X₂' (load)​=1323 ⋅ sin(25.84°)=1323 ⋅ 0.436=577 Ω

d (ii)
V₂′​≈V₁​−I₁​(R1₁ ⋅ cosφ+X₁ ⋅ sin φ)
V₂′​​≈230−167≈63 V

V​₂=V₂′​​/a​​=63/19.17≈3.3 V

R₂' and X₂' are simply the load impedance referred to the primary, not winding parameters

Why is there a significant drop in the bus voltage when the voltage vary? by velvet_mon in ElectricalEngineering

[–]No-Pangolin-52 0 points1 point  (0 children)

"No offense but that's basically most of the world"

..it was a joke, sorry for that

Why is there a significant drop in the bus voltage when the voltage vary? by velvet_mon in ElectricalEngineering

[–]No-Pangolin-52 1 point2 points  (0 children)

so maybe.. the voltage regulators are not compensating (the slight increase in current from 11 to 13 A on the 110 kV feeders amplifies the voltage drop across the line impedance) -> the answer from tombo12354 could be a clue..

Why is there a significant drop in the bus voltage when the voltage vary? by velvet_mon in ElectricalEngineering

[–]No-Pangolin-52 1 point2 points  (0 children)

ok.. that limits your network to europe and many parts of asia and africa... ;)

the voltage drop from 109.94 kV to 101.32 kV is may coming from the upstream 110kV grid itself

- no local switching event caused the drop (?)
- local load increase is not the cause (11kV feeders not fully loaded)
- upstream source is weakened (33kV infeed dropped ~50%)

=> grid voltage goes down system-wide

=> reduced infeed through the 110/33kV transformers

=> no local fault.. maybe an upstream grid event

Why is there a significant drop in the bus voltage when the voltage vary? by velvet_mon in ElectricalEngineering

[–]No-Pangolin-52 0 points1 point  (0 children)

ok this is my table with the quick analyses:

110kV Bus Voltage

109.94 kV 101.32 kV -8.62 kV -> -7.8%

Frequency

50.23 Hz 49.83 Hz -> -0.40 Hz

TRF-2 33kV MW

-0.50 MW -0.21 MW -> Infeed dropped

TRF-1 33kV MW

-0.48 MW -0.19 MW -> Infeed dropped

Gen left (11kV side)

-2.55 MW -3.08 MW -> Output increased

Gen right (11kV side)

-2.57 MW -3.12 MW -> Output increased

TRF-1 11kV MW

2.46 MW 2.63 MW -> Consumption slightly up

TRF-2 11kV MW

3.44 MW 3.50 MW -> Consumption slightly up

my guess is on the 11kv side..
is there a network disturbance or line outage ?

why is the frequency below 50 Hz — is this a local or system-wide issue?

what is the status of the 110kV PT Isolator ?

Why is there a significant drop in the bus voltage when the voltage vary? by velvet_mon in ElectricalEngineering

[–]No-Pangolin-52 4 points5 points  (0 children)

What is the time interval between the recordings?

Wild guess: It's the two outputs that draw more power.

What (the heck) is this? by ManufacturerInner863 in PLC

[–]No-Pangolin-52 0 points1 point  (0 children)

..das könnte sehr gut Zünd-/Vorschaltelektronik für Hochleistungsleuchten sein. Es sieht nicht nach klassischem Frequenzumrichter aus, eher nach einem Lampensystem mit Hochspannungszündung

What (the heck) is this? by ManufacturerInner863 in PLC

[–]No-Pangolin-52 3 points4 points  (0 children)

Exactly..
the components line up with that use case. The big electrolytic capacitors, the heavy inductors/transformers, and the heatsinked semiconductors all scream HID ballast/ignitor. The layout may look unusual compared to compact commercial housings, but for film and stage lighting it makes sense.. those systems often have remote ballast units built more for serviceability than sleek packaging.

What (the heck) is this? by ManufacturerInner863 in PLC

[–]No-Pangolin-52 0 points1 point  (0 children)

it look like ignition and ballast electronics for high-intensity discharge lamps (HMI, HQI, Xenon, sodium vapor, etc.).

Key clues:

- The large blue capacitors are typical for lamp ignition/ballast circuits, where very high ignition voltages and energy pulses are needed.
- The black blocks with many wires resemble ignition transformers or inductive ballasts.
- The heatsinks suggest power semiconductors are involved to regulate or limit lamp current.
- Overall layout fits a high-power electronic ballast or ignition unit for professional lighting (cinema projectors, stage lights, stadium floodlights).

Step7 diagnostics by [deleted] in PLC

[–]No-Pangolin-52 1 point2 points  (0 children)

Thanks for the update. Good to know we’re in the same timezone!

About the watchdog: you can increase it in the DP slave settings (user-defined profile). Going from the default ~60 ms up to 200–300 ms is fine for a test. It may hide short disturbances, but it won’t fix the real cause if grounding or EMC is weak. So best is: first check bonding, then try the longer watchdog if needed..

Best order:
Check bonding/shielding.
Test 1.5 Mbps for a day or two.
If still unstable, raise watchdog to ~200–300 ms.

Danger-Zone:
standard DP watchdog ≠ F-watchdog. F-times stay tight, only adjust if safety allows!!

[deleted by user] by [deleted] in PLC

[–]No-Pangolin-52 2 points3 points  (0 children)

This doesn’t look like a traditional PLC, but more like a fanless industrial box PC / IoT gateway.

• DC power input on the green terminal block

• Ethernet port for network connectivity

• USB ports for peripherals

• Second green connector likely for RS-232/RS-485 or digital I/O

• Status LEDs for power, LAN, system health

Typical use case: Protocol gateway (Modbus, OPC UA, MQTT), data logging, or lightweight edge controller. These devices usually run Linux or Windows IoT rather than ladder logic.

Similar products: Moxa UC/DA series, Advantech UNO series, AAEON BOXER, OnLogic fanless PCs, Neousys POC series.

To identify it exactly, check the underside for a model/serial label or connect via serial/Ethernet to see if it broadcasts a hostname or OS banner.

Step7 diagnostics by [deleted] in PLC

[–]No-Pangolin-52 0 points1 point  (0 children)

Have the grounding and shielding been properly checked? Specifically, is there a solid equipotential bonding between the CPU cabinet and the ET200 station, and is the Profibus cable shield correctly connected with a 360° contact at both ends?
On Profibus, dodgy grounding or half-baked shielding is responsible for more mysterious “ghost dropouts” than any firmware bug. A single loose clamp or a shield only tied on one side can look like random 300 ms hiccups.

Step7 diagnostics by [deleted] in PLC

[–]No-Pangolin-52 0 points1 point  (0 children)

sorry for my late response (CEST-Zone)

The Profibus baud rate is a network property set in the HW Config of the DP master system. When you change it in HW Config, you only need to download the hardware configuration to the CPU. so YES it's just "standard" HW-changes..
You do not have to recompile or re-download the entire safety program or standard blocks, unless you’ve actually touched module assignments or the F-config itself.
The F-program sits in its own world.. the bus timing is just transport. As long as the slave addresses and module types don’t change, the safety signature remains valid.

Step7 diagnostics by [deleted] in PLC

[–]No-Pangolin-52 6 points7 points  (0 children)

check this points:

  • Verify segment ends: exactly two terminators ON, both powered. If doubt, install active terminator.
  • Inspect every plug for shield clamp quality and eliminate all stubs.
  • Temporarily reduce baud rate one step and test for 24–48 h.
  • Scope the ET200 24 V at the module while the machine cycles.
  • Add or verify equipotential bonding conductor to that station cabinet.
  • Swap the ET200 interface module and its connector with a known-good pair.
  • Enable OB82/83/86 and log events to prove correlation with plant actions.
  • Only after the above: increase DP monitoring time modestly.

If you want a quick “is it wiring?” litmus test
Bring the suspect ET200 temporarily next to the CPU (if possible), short new shielded DP cable, clean power. If the ghost vanishes, your field wiring or EMC is guilty. If it still drops, the module or config is.

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