Over Voltage Problem 1

[michelin3x]

Hi!!! I am having a problem as I am not able to control the voltage. This is on a rig.

I have a PWM module giving the excitation voltage to the alternator . These also have Voltage regulator cards and Metering module which does the current sensing rather the comparison between gen voltage and the bus voltage. All these cards are racked into a motherboard. I have measured all the sensing part and the rest, I am getting the voltages I should be getting. I have swapped out the motherboard and all the modules there and tried all the gain adjustments and crap. I don't see any change in the result. Not even a tiny bit of variation. I have changed the PWM module too. Once I put my engine on IDLE its good and when I put it to RUN, the voltage shoots up above 700 and trips whereas I need to be at 600v. I removed the excitation and got the engine to Rated speed @ 60HZ. Kindly guide me as to if there could be a problem on the exciter or anywhere else or if I have problems at electronics end. The engine is an old two stroke engine. No ECM's, nothing. Mag pickups, Throttles and Fields are my wires running out on controls. Also, One of my techs told me that the voltage he measured on the fields while it was on RUN was around 250V AC. The engine says it should be a maximum of 70V at full load. Is this a valid result?. Does this point to a fault on something?.. Kindly help me with any suggestions you have,

 

[catserveng]

On the generator nameplate you should (hopefully) see data for field volts and field amps, both in DC. Those two numbers can let you figure out the field resistance, so if your rated at 70 volts and say 10 amps, then your field resistance should be 7 ohms. Now lift F1 (+) and F2 (-) from the terminal strip on the back of the mother board and measure the resistance, should be pretty close to what you calculated its supposed to be. If it is, likely your exciter is NOT the problem. If you are in fact seeing over 200 VAC at the F1 and F2 terminals, sounds like the voltage regulator is over driving the field output. Has anyone been working on the wiring for the regulator circuits? 240 VAC sounds typical for a lot of SCR drive systems voltage regulator power input voltage. You said this rig has 2 stroke engine, like old Detroits? So likely you have an old SCR house as well? What system is this, like a Ross Hill or IPS?

Typically things that will cause the voltage regulator to go full output are,
Loss of voltage sensing
Open Droop CT circuit
Open voltage adjust circuit

Mike L.