Reverse Power Problem in Cummins Generator.


Thread Starter


i had a problem with Cummins Generatror ( model KTA-50-G3). that is reverse power occurred when generator loaded for 3 or 4 hours. i checked all the connections of CTs it's all OK. also i tested the control sittings it's all OK to. what would be the problem?

please help.
Detection of power relies on PTs as well as CTs.
<pre> Fuel = Power

No Fuel = No Power</pre>
Be sure of any hydraulic fuel control system components (if any).

I have also seen this problem before when the fuel supply is restricted. If the liquid fuel is fed from a large tank via a forwarding pump, make sure all is well with strainers and the forwarding pump motor/motor starter and automatic controls.

Lastly, if it's always occurring at approximately the same time after being started/loaded, this type of problem can occur when an electronic component gets too warm. By the time you get to the unit, it may have cooled sufficiently the problem appears to have "disappeared."

Please write back to let us know what you find!
all the PTs and CTs connections are OK, also the fuel reached OK. i think the problem is electronic components get warm because the engine stopped suddenly and start again like some one turn it off and on. but why this problem occurred at this time because the weather is winter now here. may the control system malfunctioned ? but how that if the generator working for more than three or four hours ???

This is NEW information.

If the engine stopped suddenly, that could be due to a fuel flow issue, yes? And if there was an "automatic" command to start/run the unit, then it could have been interpreted by the control system to re-start and re-synchronize the genset. Yes?

From your first message it sounded as if this has happened more than once, and it was not apparent the diesel had "died" and suddenly re-started. How many times has this occurred?

Reverse power relays are actuated when the energy flow-rate into the prime mover (the fuel into the diesel in your case) is not sufficient to keep the generator spinning at synchronous speed. A fuel restriction or some other issue preventing fuel from getting into the diesel's cylinders would result in a reverse power event when providing power to a load/grid.

What was the frequency of the load/grid doing at the time of the event? Frequency fluctuations can have adverse effects, especially if they are sudden and large.

Where is the diesel electronic control unit located? How dirty is it? They usually have some kind of "forced" air flow over them for cooling; are you sure it's not blocked/restricted?

Lastly, electronics are not perfect. Even "industrial" electronics. We don't know (because you haven't old us) how old the electronics control unit/diesel gen-set is, how much use it gets, how well maintained (or not) it is/has been--but rest assured, electronics, heat and humidity do not play well together over time.

Just because it's winter "outside" doesn't mean electronics don't generate heat and need to be kept clean and cooled and "dry." There are simply too many intangibles for us to be able to say with any measure of certainty what happened at your site, because we're not there and you haven't told us very much, and it seems we don't have much of the whole circumstances surrounding this problem.
firstly, thanks for your replies i'm really appreciate that.

> How many times has this occurred?

More than 7 or 8 times it has been occurred. Now every time you start it, it is running for 3 hours and that problem occurred again. When the generator stopped all the parameters are ok: frequency 60 Hz ( may + or – by 0.1 or 0.2 ), voltage 440 V (generator output similar to busbar ).

> Where is the diesel electronic control unit located? How dirty is it?

Diesel electronic control located in front of alternator away from engine and it is clean and cooled by natural air follow.
How old the electronics control unit/diesel gen-set is, how much use it gets, how well maintained (or not) ?

The generator (among other 15 generators) was working in this project for two years as prime generator. It is well maintaining.
In addition all the mechanical part checked filters, diesel flow, turbo … etc. also we changed all control cards like analog card, digital card, engine interface, costumer interface, bus PT, CT and PT module, governor module and AVR to. But I think the problem maybe in the EPROM of Digital card affected by heat. I request new EPROM from the company I wish that would solve the problem.
It could be very unexpected cause, while your engine seems to be stopped due to shortage of fuel supply, while there are no alarms on control panel when genset stops. it may be shortage of fuel to be supplied to the engine. i have an experience with 3 gensets in parallel operation. 2 of them stop suddenly after 2 hrs. the cause was as follow, the fuel tank breather was partially clogged. when gensets run for 2 hrs the pressure inside tanks become suction pressure (-ve) and engine fuel suction pump become unable to suck after 2 hours then engine stops. after while gensets can start again after faults reset. the breather and fuel lines adjusted and system run smoothly.