Timeline for TRIAC gate resistor keeps getting burned
Current License: CC BY-SA 3.0
20 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jan 23, 2014 at 21:13 | answer | added | Spehro 'speff' Pefhany | timeline score: 0 | |
| Jan 23, 2014 at 19:20 | answer | added | hondabones | timeline score: 2 | |
| Sep 9, 2013 at 15:15 | history | tweeted | twitter.com/#!/StackElectronix/status/377087954701008896 | ||
| May 16, 2013 at 1:29 | comment | added | Brian Wang | @DaveTweed I think that's it! That's why 3Q TRIACs do not fry the resistor. I guess for the circuit to work with 4Q TRIACs, a proper snubber RC should be added. Thanks for the pointers. | |
| May 15, 2013 at 15:52 | comment | added | Dave Tweed | Have you read the Wikipedia article about TRIACs? It has a lot of detail that I think is relevant to your situation, particularly the part about commutating. I think you're getting very large, very narrow spikes of current through the gate resistor each time the main triac tries to turn off at a current zero-crossing. | |
| May 15, 2013 at 1:03 | comment | added | Brian Wang | @pjc50 Could you elaborate a bit more about the gate current? Thanks. | |
| May 15, 2013 at 1:02 | comment | added | Brian Wang | @DaveTweed Do you mean that excessive voltage spikes when the gate of the TRIAC is being turned on and off is causing the resistor to burn up? I tried hooking up a scope but the waveform of 220V AC gets clipped... I also tried to measure the current flowing through R85 but my DMM has trouble measuring the short pulses. I did put the scope across R85 and saw a max of 0.7V. If my calculation is correct, that does not exceed the resistor's power rating. How/Where do I measure/observe the stress on R85? Thanks. | |
| May 14, 2013 at 12:37 | comment | added | Brian Wang | We have also tried Q6008RH4, which is a High-Comm triac, while BT137 is an ordinary 4Q triac. With Q6008RH4, the resistor does not get burned or not as easily (we have not seen it burned yet). I think there is something fundamentally wrong with the circuit. I am not sure about the values of the resistors and how much current flows through them. | |
| May 14, 2013 at 12:31 | comment | added | Andy aka | Dave is quite correct. For inrush current avoidance (when the magnetic material of the inductive core saturates) you need to switch the circuit initially when the 220VAC is near a peak NOT as it passes thru zero. | |
| May 14, 2013 at 12:19 | comment | added | Dave Tweed | If that resistor is burning up, you must be forcing something on the order of 100 mA RMS through it, which is also close to the absolute maximum for the optocoupler. Was this circuit originally designed to handle inductive loads at 220V? Keep in mind that with reactive loads, the zero crossings of the current do not align with the zero crossings of the voltage, and this puts a lot of stress on this type of circuit, which is often rated "for resistive loads only." | |
| May 14, 2013 at 12:18 | comment | added | Brian Wang | @DaveTweed Thanks. I will include the links next time. :) | |
| May 14, 2013 at 12:11 | comment | added | pjc50 | How is the gate current supposed to be limited? Aren't you going to get 10ma * 220V = 0.2W through it? | |
| May 14, 2013 at 11:57 | comment | added | Dave Tweed | If you include links to the datasheets for the components you're using, it makes it a lot easier on people who might be interested in answering your question. | |
| May 14, 2013 at 11:55 | history | edited | Dave Tweed | CC BY-SA 3.0 |
add links to datahseets
|
| May 14, 2013 at 11:54 | comment | added | Brian Wang | The load is across LUG10 and AC_NEUT. I have edited the post. Thanks. :-) | |
| May 14, 2013 at 11:53 | history | edited | Brian Wang | CC BY-SA 3.0 |
Added where the load is connected
|
| May 14, 2013 at 11:36 | comment | added | Andy aka | Where is the load connected? | |
| May 14, 2013 at 11:36 | review | First posts | |||
| May 14, 2013 at 11:57 | |||||
| May 14, 2013 at 11:24 | history | edited | PeterJ | CC BY-SA 3.0 |
Inline image
|
| May 14, 2013 at 11:19 | history | asked | Brian Wang | CC BY-SA 3.0 |