Hi,
I need to control a spot welding 200kva single phase transformer using scr
phase control, please advise methods and what precautions are necessary
for zero crossing sensing and scr gate triggering. the voltage is 400vac using
two phases.
Regards
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1
on: Yesterday at 05:41:06 AM
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| Started by max - Last post by max | ||
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2
on: April 19, 2025, 04:53:04 16:53
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| Started by Ahmad_k - Last post by Catcatcat | ||
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They can even have higher voltage
LMZM2360xxx Vin - 4V to 36V TPSM5601xxx Vin - 4.2V~60V |
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3
on: April 19, 2025, 04:16:29 16:16
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| Started by Ahmad_k - Last post by Ahmad_k | ||
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Please pay attention to such modules LMZM23601SILR...TPS82150SILT... from Texas Instruments. https://www.ti.com/lit/ds/symlink/lmz21701.pdf https://www.ti.com/lit/ds/symlink/tpsm861252.pdf https://www.ti.com/lit/ds/symlink/tpsm861252.pdf .... In terms of cost to size ratio, DCDCs are very attractive. Interesting but outside of my requirements. it cannot handle 30V input. |
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4
on: April 19, 2025, 11:52:41 11:52
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| Started by Ahmad_k - Last post by Catcatcat | ||
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Please pay attention to such modules LMZM23601SILR...TPS82150SILT... from Texas Instruments.
https://www.ti.com/lit/ds/symlink/lmz21701.pdf https://www.ti.com/lit/ds/symlink/tpsm861252.pdf https://www.ti.com/lit/ds/symlink/tpsm861252.pdf .... In terms of cost to size ratio, DCDCs are very attractive. |
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5
on: April 19, 2025, 11:04:38 11:04
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| Started by Ahmad_k - Last post by Sideshow Bob | ||
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Yeah the datasheet state max frequency should be 1.5MHz
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6
on: April 19, 2025, 10:09:34 10:09
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| Started by Ahmad_k - Last post by Ahmad_k | ||
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Yes clearly it is fake chip. One thing I noticed also when I increase Vin is that the switching frequency is slightly decreased to 1.5Mhz which is another sign of fake chip.
the attached image shows a genuine chip on a device drawing 50mA VS my PCB drawing 50mA, same Vin and same components value, only the chip is different |
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7
on: April 19, 2025, 09:36:12 09:36
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| Started by Ahmad_k - Last post by dennis78 | ||
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Ahmad_k: "I noticed the switching frequency was 1.75Mhz" It's convincing evidence in the direction of suspicion regarding ic. They often just overwrite labels on similar pin compatible ics or sell pass failed of quality control or bad clones. My experience with digital ics from China is in most times ok, but analog/mixed and similar ic's is not good even I use it significantly below declared characteristics and for simple purposes.
If you have any wishes you can try with <22uH but with open core option (Of curse, Vin will be limited but >12V as now ). That inductors are generaly more suitable for higher freq. Be careful when connecting to keep parasitic capacitance to a minimum. If not, we expect report for 15 days |
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8
on: April 19, 2025, 09:07:48 09:07
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| Started by Ahmad_k - Last post by Ahmad_k | ||
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I am sure I am using 1A coil. also if the coil was saturated it would heat at least a little. the coil still cool even if the chip heated above 13V
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9
on: April 19, 2025, 08:45:26 08:45
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| Started by Ahmad_k - Last post by Sideshow Bob | ||
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This is me just spitballing. But are you sure the inductor is up to snuff current and frequency way. The datasheet mention that saturating the inductor may cause the device going into thermal shutdown mode and the possibility of damaging the inductor. See the datasheet page 7-8
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10
on: April 19, 2025, 07:33:20 07:33
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| Started by Ahmad_k - Last post by Ahmad_k | ||
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Check waveform voltage on C8. C8 shouldn't be under 100-150nF (C8 is for supply driving circuit in active cycle so it must not be too low). I thougt add to them parallel 1-10nF (I not expect too much from this but try). For inductors you used, what is declared current? (I ask beacuse of possible saturation. Bigger inductance for same size mean lower saturation current...). I suspect on IC, but you check all other (beacuse of very high switshnig freq these ics are sensitive so layout also can cause different problems)... 1A max current coil. So it should be safe. I still suspect the IC as you said because I noticed the switching frequency was 1.75Mhz which is outside the limitation. I will order from trusted reseller and report back in a week or two |
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