Timeline for Voltage dip at source side during heavy loads due to Internal Resistance
Current License: CC BY-SA 4.0
6 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Sep 9, 2019 at 5:34 | vote | accept | CommunityBot | ||
| Sep 8, 2019 at 20:29 | comment | added | Bruce Abbott | For fair comparison against the regulated supply I am assuming that both put out 12V with no load. The difference is 'minimal' anyway, ie. close enough to be ignored in this rough analysis. Wiring resistance is another matter, but would be considered a part of the 'power source' from the device's perspective. The OP said 'During high currents, some voltage is dropped across the internal resistance of the voltage source' so I think (s)he is aware that both resistance and current are required to cause voltage drop. | |
| Sep 8, 2019 at 18:07 | comment | added | Maple | I think the equation for hot bulb misses supply resistance, should be 12/25. Nevertheless, both examples show that supply resistance technically does not cause the drop, as OP question implied, only the current does. Reduce source resistance to zero and there still will be a drop due to wiring (OP is asking about "dip that is observable at the load side"). And with regulated supplies this whole question of source resistance becomes moot entirely. | |
| Sep 7, 2019 at 21:42 | comment | added | Bruce Abbott | Example 1: 12V 1A unregulated supply with Ri = 1 Ohm. Connect 12V 6W lamp which normally draws 0.5A. Cold resistance is 2.4 Ohms so initial current is 12V/(1+2.4) = 3.5A and voltage is 12-(3.5*1) = 8.5V. Upon heating up the bulb resistance increases to 24 Ohms and voltage is 12-(12/24*1) = 11.5V. Example 2: 12V 1A supply with regulator, current limited to 1.2A. Initial voltage is 1.2A*2.4 Ohms = 2.9V. Bulb heats up (slower, due to lower current) to 24 Ohms and voltage rises to 11.95V (regulated Ri is 0.1 Ohm). regulated supply has lower Ri, but voltage sags more when overloaded. | |
| Sep 7, 2019 at 15:28 | comment | added | user220456 | Thank you. But could you just give a simple example like scenario with some numerical , easy to grasp. And finally, you are saying, the bottom-line is Internal Resistance, right? | |
| Sep 7, 2019 at 8:03 | history | answered | Bruce Abbott | CC BY-SA 4.0 |