Need 120A current regulator to keep alternator from burning up if load goes higher

Thread Starter


Joined Jul 23, 2020
I have a 12V (actually 14.2VDC) 200A vehicle alternator with which I wish to power a load that I want to keep to only 120A or lower. I don't care too much about precision (within 10A drift or even a little more would be OK) but the circuit would needd to provide this current continuous-duty at this high amp rate. I have seen a couple of other circuits here offering a current limiting circuit but they don't seem exactly to fit my needs as they don't approach the level of abuse (recovering from near short) my device would need to recover from. This current limiter would be something that, viewed from another perspecctive, could protect from near a short circuit and with any load even down to very low resistance across the output terminals yet, no matter if the load was 40A or 300A, the output from the device could never go above 120A. A bonus would be if a pot could be used somewhere to adjust that top current llimit, e.g. perhaps it could be adjusted up and down to a value of 120A +/- 30A. Thank you.


Joined Nov 18, 2012
You would probably have to come up with a circuit which limits rotor current to a certain percentage of full output. Maximum current is dictated by rotor current + th design of the stator windings and driving it over that limit would result in diode or stator failure. To underdrive it ata constant rate you would have to use a PWM circuit to the rotor and perhaps have some sort of feedback system to keep it stable. This circuit would replace your IVR.


Joined Feb 24, 2006
If the load requires more current than the alternator can supply, the solution is not a regulator. You either find a way to reduce the load or you get a beefier alternator.


Joined Feb 24, 2006
The TS said he has 200 Amp vehicle alternator That he doesn't want to put out more the 120 Amp
into a load
Yup -- I missed that. I thought he was worried about destroying the alternator if it supplied more than 120 A to a load.
I can't help but think that a better title might have added some clarity.