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| Lab Power Supply - The Lost Current |
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| radoczi94:
--- Quote from: xavier60 on January 31, 2018, 08:29:22 am ---It's odd that the Emitter resistors are 0.2 ohms and the shunt resistors are 0.22 ohms. I would run the output into an ammeter or a shunt resistor to know the output current then measure the voltage drop across all of the low value resistors in the current path to make sense of it. Maybe this is what you have been doing? --- End quote --- I used the same kind of resistors for the shunt and the emitter resistors. Measured the voltage drop across the emitter resistors too, they had around 1,5 A flowing thru each. Nothing odd there. Tried the same kind of resistors as a load on the output, they had 0,65V voltage drop at 3A, so the resistors are correct value. |
| xavier60:
--- Quote from: radoczi94 on January 31, 2018, 08:36:29 am --- --- Quote from: xavier60 on January 31, 2018, 08:29:22 am ---It's odd that the Emitter resistors are 0.2 ohms and the shunt resistors are 0.22 ohms. I would run the output into an ammeter or a shunt resistor to know the output current then measure the voltage drop across all of the low value resistors in the current path to make sense of it. Maybe this is what you have been doing? --- End quote --- I used the same kind of resistors for the shunt and the emitter resistors. Measured the voltage drop across the emitter resistors too, they had around 1,5 A flowing thru each. Nothing odd there. Tried the same kind of resistors as a load on the output, they had 0,65V voltage drop at 3A, so the resistors are correct value. --- End quote --- And the voltage drop across R25 or R23 indicates only 1 amp? |
| radoczi94:
--- Quote from: xavier60 on January 31, 2018, 08:51:54 am --- --- Quote from: radoczi94 on January 31, 2018, 08:36:29 am --- --- Quote from: xavier60 on January 31, 2018, 08:29:22 am ---It's odd that the Emitter resistors are 0.2 ohms and the shunt resistors are 0.22 ohms. I would run the output into an ammeter or a shunt resistor to know the output current then measure the voltage drop across all of the low value resistors in the current path to make sense of it. Maybe this is what you have been doing? --- End quote --- I used the same kind of resistors for the shunt and the emitter resistors. Measured the voltage drop across the emitter resistors too, they had around 1,5 A flowing thru each. Nothing odd there. Tried the same kind of resistors as a load on the output, they had 0,65V voltage drop at 3A, so the resistors are correct value. --- End quote --- And the voltage drop across R25 or R23 indicates only 1 amp? --- End quote --- Yes. And the series connected current meter shows that too. |
| xavier60:
Although you have checked, there must be a short somewhere bypassing current around the shunt resistors. What supplies input power? Can you take some photos? |
| radoczi94:
--- Quote from: xavier60 on January 31, 2018, 09:00:15 am ---Although you have checked, there must be a short somewhere bypassing current around the shunt resistors. What supplies input power? Can you take some photos? --- End quote --- The power is supplyed by a 250VA transformer, a cooled rectifier bridge and 10kuF 100V caps. That board ind the front-middle is just only a reverse polarity protection board, 2 diodes and a fuse. It's not attached to the circuit right now. The small board on the left is a small supply for the relays and the fan control. And yes, the non marked wires have a reversed polarity on the rectifier board output, I corrected that before powering on.https://drive.google.com/drive/folders/1BI_EM4ImJGpWINuNeS3gs_Wgnjbidrzf?usp=sharing |
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