The main causes of voltage drop in generator

Some common reasons are :
1). Load applied to generator exceeds capacity, typically would cause machine to slow down, drop frequency and voltage typically cause exhaust black stacking and depending on the overload and protection settings could cause machine to stall.

2). AVR Voltage gain set too low to respond to load being applied.

3). If AVR feedback is from generator bus VT and voltage dips too far, all excitation could be lost and would typically result in an undervoltage and overcurrent trip.

4). Speed control gain set too low to respond to load being applied.

5). Mechanical issue such as failing turbo unable to provide enough air of high enough pressure while taking on load which will cause machine to slow down and in some cases stall on high load application with sufficient reduction in speed voltage will also lower as well as frequency. In this condition you'd probably also see exhaust black stacking.

6). Mechanical issue such as fuel injection clogged or fuel filters clogged causing the machine to be under fuelled to handle load application and may cause machine to slow down, which in turn would drop Hertz and Volts.

7). There's a whole truck load full of other reasons why this could happen.


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12/5/2022 12:55 PM
Why electricity meter is is counting units even though Mains off and DG running?
12/3/2021 6:00 AM
Nice site
1/19/2021 6:54 AM
My brute 3500 watt generator bogs itself way down about every 15 to 20 minutes to the point of where it almost shuts down but it doesn't it takes itself back to running normally all by itself. It normally powers 5 lamps and 2 tv's and sometimes a small fan
11/21/2020 4:45 AM
How can I fix number 3,it supplies current but fail to pick pump unlike before
11/16/2020 9:34 AM
I would like to purchase a 5 kw 3 phase military generator for two uses... 1. I would like it to pump water to a holding tank from my well which is a 2.5 well.   2. I would like to use it for filling a battery bank.  Are these things possible with this generator?  I have no knowledge of generators.  I am a 64 year old woman who is just trying to prepare for what ever might be coming and have never dealt with generators and want a diesel because you can make diesel .  I am also dabbling in that too lol. So if you can just throw me a bone I would greatly appreciate it:)
8/3/2020 1:29 PM
Congratulations! This ranks right up there as one of the dumbest, most useless sites on the web!
8/1/2020 1:40 PM
MEP005A military generator only works with field manually excited...
While excited it ran a drop light and fan normally. Soon as I let go of the switch that manually excites I lose electricity. Diesel power unit functions properly.
7/10/2020 3:00 AM
its a et 950 model small single phase with capacitor generator. it gives only 40 volt when excitted with battery
6/21/2020 11:16 PM
I have a 30kw 240v single phase generator that only seems to hold approximately 27kw. Voltage at no load is 240v and 61hz. At 80% load, 100amps, capacity I have 230v and 60hz. The generator only seems to hold 90% of the load that it is supposed to, 112amps, until it begins load shedding.

My main question is why is there such a voltage drop when the frequency did not drop nearly as much. I would think the prime mover is still able to carry the load since it is moving at the proper frequency. What am I missing?

Northern Lights 30kw M9444W
5/24/2020 3:42 PM
I have an issue with my 900 watts 2 hp portable genset! I have noticed that i got only 6.8 volts AC output instead 120 volts AC while running! So then i did some field flashing while the genset running using a 12 volts car battery and connected on the female output socket for a few second but still did not have a right output voltage! So any recommendations or advice you can give? Your response is highly appreciated. thanks
4/23/2020 1:38 AM
Hello, I hope you don't mind answering the following question for me:
I'm interested in getting a generator like a Champion 5.5KW dual generator. As you know, it's 240 VAC is two phase. I also want a 230VAC, single phase arc welder. I've seen people weld, using  L14-30 to 14-30 adapter with no issue. I think, however, that would create an unbalanced load and, eventually, damage the generator. What are your thoughts, sir?

Thank you,

William Reynolds
3/10/2020 7:10 AM
My pump is running when connected on electrical gride
But the contactor in the pump control board is running interchangibly on and off with in a second sothat the pump can not run how can i solve this problem.
3/8/2020 10:14 AM
My 125 kva generator showing Hz and V.How can i solve problem in emergency
3/6/2020 1:42 PM
My Cummins as55d5 is operating well but with no AC input
3/3/2020 1:22 AM
Low voltage,120 volts on one leg,50 volts on the other,this happened last year,put a new voltage regulator on it,solved the problem,used it 2months ago ,fired it up and run great for about 15 minutes and then stalled the motor,any ideas would be great,thanks,Davy
2/22/2020 10:40 AM
Its good
2/10/2020 11:07 PM
My generator 20KVA still runs nicely under load but voltage is no longer 415. It has dropped to about 380v even with no load, each phase instead of being 240v is now about 205v still 50 HZ, load up all seems to work fine an holds voltage loaded or unloaded.... any ideas?/ suggestions?
1/11/2020 8:04 PM
This is a new Generac generator 7.5kw .  The out put of the generator goes from 240 v to 120 across the 2 main leads,  when the load is applied . Shut off the load and the output is 240. Amp draw is only 15 amps . This is not
just voltage drop . it goes to 59 or 60 volts total on each leg .
1/11/2020 7:57 PM
The out put of the generator goes from 240 v to 120 when the load is applied . shut it off and the output is 240. Amp draw is only 15 amps
11/19/2019 3:56 PM
Generator can only be set from startup to  352 ac volts with NEW AVR, SAME AS OLD ONE, run for 10 min and voltage go slowly down to L-L 240 and L-N 140. What can be the cause.
7/14/2019 8:14 PM
I have a military John Hollingsworth diesel generator with the white engine starts runs fine hit the switch generator turns on once I put a load on it it totally loses all its power not the engine just the voltage part I need a little help please
7/2/2019 5:27 PM
I was running 🏃 my 40kva generator, it shutdown unexpectedly what might be the cause,
6/22/2019 12:46 PM
Good day Sirs,
I have this Sdom's Generator 440 kva that the stator winding breasted, after rewinding the voltage cant go up to 415v ,voltage now is 339v and the main rotor winding also heat.  I need your help.
3/20/2019 10:50 PM
Sometimes I start my generator and it puts out voltage and sometimes it won't. Would this be the Automatic Voltage Regulator?  
3/18/2019 11:23 AM
I have a problem with my generator, I replaced a new alternator. i ran it and put a load on it while its running the generator voltage and hertz is up and down and automatically shut donw  when thje hertz is 46 also when it comes to 55 hertz. any idea what is wrong on this generator?
2/11/2019 8:34 AM
My 4.5 kva diesel genset will only produce 50 volts when started with no load at all .motor seems to be running well.whatcould be the cause or what could be the problem?

8/19/2018 8:29 AM
I have a 3 phase genny that in sed in a workshop to run it during power outages, it ran out of fuel and know when i run it the two x 3 phase hoist motors wont run properly the just jerk forward but dont actually move

When i turn the change over switch back to mains they work as normal

I had a sparly check it out and he find 400 volts between one set of phases and the other two cycle from 200 to 400 volts and you can see that on the multi meter voltage between phases 2 & 3 going up and down continually.

It has him stumped so im doing the research for him

Any ideas please
8/8/2018 6:21 AM
Am working with Enviroserv uganda working as mechanic we have a 250 kva generator it has failed to start it indicates that generator under voltage what could be the fault

7/9/2018 11:19 AM
i have 125KV generator , that is happening voltage drop , i need to know the problem , please can u suggest me
5/22/2018 12:10 AM
My 1000kva generator gives only 150 v on all phases any probable cause . Thanks .
Huzaifadude23@Gmail. Com
5/18/2018 2:20 PM
North Star 8000 pro series gen, used to operate 220v 2 hp submersible pump. Only getting about 180-190 volts out of 220 outlet, 110 outlets about  90 v.  Same with or without load. Motor seems to running normally(Honda). Is there a way to adjust output. Thank you
5/10/2018 4:28 PM
Really helpful..
5/10/2018 4:16 PM
Can load imbalance can cause a low hz problem in gensets?
4/21/2018 7:50 AM
my gasoline generator's low voltage instead of 220 v but he generate 167 v what to do?
3/8/2018 6:02 PM
we have a particular generator called the herculesD198 ER and its dropping voltage what could be the cause
1/28/2018 5:41 PM
1/11/2018 6:08 AM
Hi the genny runs 110v grinders and drills but will not power paddle mixer now
11/19/2017 9:44 AM
I am using a 20kva lister diesel genset  and when a load of three air conditions discharge is 4.2MPa and suction 1.5MPa the voltage drops to about 196 volts and frequency drops to about 45Hz what is the cause of voltage drop pls
11/15/2017 3:33 PM
My name is AYO and my e-mail is

I need an aswer to this question: What is the probable causes that frequency not come up after geneator start.
10/20/2017 9:34 PM
Our 220 gen was working fine until it was inadvertently hooked up to the utility input which caused as you can imagine a significant overload. After this was corrected it only produced 50 amps
Motor runs fine and starts right up. Any ideas on what might be causing this problem.
This was during our 14 day power outages in the Sonoma Valley fires.
9/26/2017 2:19 PM
My generator  is 3 kva  bur write now  I am not getting volteg  one single bulb 100 w not on only is filament is red why

What. Is problem
9/14/2017 8:35 PM
hi there, just a quick question, my generator will power a kettle and electric ring etc but will not power my 3 amp internet box ?? if the kettle and the internet box are plugged in at the same time, they both work ?!? when kettle is unplugged, voltage reading on generator drops to 0. any ideas ? many thanks for your time.
8/9/2017 6:22 PM
Thank you sir? Can power output slow down while a built in voltmetter reads 240v ac
8/6/2017 2:58 PM
My 3kva generator giving only 65-70 volts. Why?
6/30/2017 5:14 PM
This is Ramakrishna
I have mahindra 15kva 3 phase diesel generator
While power gone we will switched on generator
We have telecom load on generator
After half an hour running generator suddenly it's engine slow &voltage drops suddenly after that our contactors open load disconnected on generator
Again voltage raised to 440volts
What would be the reason for this
Please explain me how can I know avoid this
6/23/2017 4:49 PM
HI i have load of around 50A for 82.5 kva gen, at the time of starting DG my lighting works well, but after 5mins its starts fluctuating , while i check my voltage form DG control panel its stable as 235V per phase , but lights are fluctuating., can any one help
5/16/2017 10:58 AM
I have a 300kva generator in a plant so sometimes it starts up well 525volt and everything runs smooth and other times it stop on gen low voltage what can be the cause?
4/29/2017 8:59 AM
Hello Sir...
I have a generator with a total running life of about 700hrs. It has been working perfectly okay until last night when it suddenly developed fault.
Normally, it carries all my lighting bulbs & other appliances (including refrigerator). But as it is now, it can no longer carry the refrigerator. Once I switch it 'on', the voltmeter drops to zero and every light goes 'off'. If switch 'off', the voltmeter goes back to 230v and every light comes 'on' .
I have try putting everything 'off' and put 'on' only the refrigerator but the same thing happens.
In summary, the voltmeter stays at 230v while the generator is running on lights and small appliances but drops to zero once I add bigger appliance like my refrigerator. Thanks in advance.
Model: Lutian, LT3600 EB8
Rated output: 3.5KVA
4/21/2017 5:53 PM
Thanks and useful information was learned by us...

Tahir Mohammad Hassan
4/18/2017 6:05 PM
my generator 110 kva .. shutdown after High frequency with higher Tpm .. I adjusted fuel pump throttle after that also i am getting  same fault .. pls help me to get rid of from this breakdown
4/14/2017 6:58 PM
I have
4/10/2017 8:15 AM
but when i try to change the position of the main incomer breaker the voltage increases
4/8/2017 5:11 PM
Hello My Name is "Ubaid''
Sirr Please...!!!!
Give the Reason of voltage reduction of alternator on Load.

Give sOme important Reason's..

I Shall be very thankfull thankfulll.

MY Mail is :  (

4/8/2017 5:07 PM
Siirr Please..!!! Give the Reason of voltage reduction of alternator on Load...?
3/31/2017 11:10 AM
i have a challenge with my generator it runs for only ten minutes,then drops voltage,how can i solve this

3/12/2017 3:56 PM
I start my generator in the voltage fluctuates up and down the lights flicker trying to figure out why generator runs fine
3/9/2017 6:01 AM
when rain falls my ( VGF H24GL WAUKESHA.S/N C-17725/2 ) keeps shutting down and under frequency will show up, why is this?
3/9/2017 2:07 AM
I should have mentioned (DUH) the post of mine above......  The reason I suspect bad propane is because the only thing that has changed on my entire house / system IS THE FACT THAT I HAD THE PROPANE TANK FILL 30 DAYS AGO and since then, our stove burners show orange flames at the tips and full length streaks of orange too......and our home (LP) heater seems to run LONGER to get the home up to temp each time the thermostat kicks the heat on.
3/9/2017 12:16 AM
How about poor / contaminated propane? I have a 16KW LP genset- operated perfect for years (still runs great), BUT last time we lost power it kicked on, ran just fine, until a 220 circuit kicked on (water heater, clothes dryer - any 220V).  Then it "lugged down" and was working HARD to hold high RPM (which it failed to do) a result, nothing else 120v in the house was usable until the 220v circuit kicked back out. When the 220v load was removed, rpm went right back up, no more lugging and all 120v house things worked fine.
3/7/2017 3:59 AM
pls help a 2200 series Perkins, when loaded , the gen drops.

2/19/2017 1:42 PM
Pls. what can i do to my generator that has only 120V output to get 220V?
Thank you.
2/18/2017 2:11 AM
how can we rectify that can of problem sir
2/9/2017 8:45 AM
please can you explain how to set or fix gen low frequency and low volts
1/24/2017 9:55 AM
I have Stamford generator
The problem was
Generator  no load and with load also voltage   is going down
From AVR I increase the voltage up to 385v. Still same no load also voltage is going
Frequency ok
What would be reason
Pls e mail me..
1/17/2017 3:02 PM
When generator with load voltage is going to reduce and sometime no load also voltage is going to low
what would be reason..
Give me any idea
12/30/2016 9:11 PM
During starting of emergency generator voltage drop from 440 to 220 or 200. What is the cause?
12/29/2016 2:46 AM
What type of loads are you trying to connect? If they are highly inductive or involve any type of high inertia loads, then your generator may not be able to provide enough starting torque or voltage support to successfully start them.

Low power single phase alternators often have simple excitation systems that use the output of the alternator to provide the field current, and are incapable of supplying high inrush current loads.

Small generators like this draw their excitation power from the output of the generator, have no AVR, nor any Boost capability; i.e., their voltage falls as the load increases. The size and type of load makes a huge difference in the generator's ability to maintain the voltage in an acceptable range when equipped with a simple excitation system that operates open loop.

Where did the excitation power come from, the generator terminals, or a dedicated extra winding in the stator? If it comes from the output terminals, then the "voltage regulator" is usually a LM part number whose job it is to limit the voltage to the field under no/light load, but it can do nothing to support the terminal voltage as it falls due to large inductive loads being applied.

A separately derived excitation source will indeed attempt to raise the excitation level to the current limits of the field/stator winding, but such sophistication is usually not found in consumer level single phase generators due to the cost factor.
12/29/2016 2:36 AM
We have a 10kw/43 A / 230V single phase A.C Brush Generator which works properly when there is no load or low loads (less than 10 A) but when we connect more loads to the output, the voltage suddenly drops ( it goes down to 30 V). What can be the reasons?
12/18/2016 6:20 AM
If I plug my laptop to my little generator the power would drop but if removed it come up why.
Please I need your help
12/4/2016 7:21 PM
my diesel generator will shut down while running and will display an alarm abnormal acb trip, what are the causes why my acb will trip while the load at 70 percent?
11/21/2016 9:43 PM
Hallow can you assist me with this I have may generator giving the error of over ac volt . What could the problem
11/21/2016 6:53 PM
Can faulty capacitor cause voltage/current drop
11/21/2016 9:21 AM
when a diesel generator developed such fault (voltage drop), which of the causes do we need to start from?
11/20/2016 12:49 AM
Dear sir .when we start generator .some time start properly but some time .stop due to .(common voltage/frequency fault alarm )if running 2 o 3 days suddenly stop for this alarm .any solution sir.thanks
11/14/2016 11:37 AM
i have a 3 phase stamford generator run by perkins engine. the generator trips on undervoltage while on load. what might be the cause?
11/11/2016 5:08 PM
I have an opposite effect on my Volvo 580KVA generator. When almost 40% of the full load is removed from the generator in one step, not only there is no voltage overshoot, but, on the contrary, the votage drops from 380V down to 320V momentarily before recovering.
This is a peculiar beaviour and I have not found a solution. The load removed is a motor (inductive load) running on a soft starter.
Any suggestions?
11/10/2016 10:40 PM
my 3000 series Shrewsbury is over speeding and I don't now what to du
10/23/2016 2:10 AM
My generator not giving any output power
10/20/2016 7:03 PM
I have a model 40008 champion generator that at times it drop voltage. This could last maybe 5 minutes or as much as several hours. I really don't want to get rid of it as it was my brothers.
10/15/2016 5:09 AM
Every now an then my genartor the volts will drop an only put ut a lil power I was messing wid plug wigglein it an it started work good but every now an then it will drop any ideas
10/6/2016 6:49 AM
During engine idle operation the generator start hunting l.e hnmmm, hnmm and all the control signal will lost. As result it shortdown on underfrequency. Pls what is the caues for this?
10/3/2016 3:35 PM
Thank you the information.
9/18/2016 6:35 AM
Hello All,
I have a three phase connection for my duplex house and hence the ACCL was badly burnt due to sudden surge from Electricity pole. Hence as the cost of the ACCL was high I replaced with a manual Changeover switch. But the output is not controlled and as it is direct from the generator, due to fluctuations in the Generator output My appliances are blowing out one by one due to uneven voltage. Five LED tubelights, microwave was burnt though not switched on, and many other appliances are burning out. Hence I have now disconnected the Generator supply to my house.

Any suggestions how to control Generator output fluctuations as it is directly from generator to my house.

My email Id is

Please provide cost effective solution.
Thanks in advance.
9/15/2016 9:20 AM
Thanks for the information....
9/14/2016 5:03 AM
What is the probable causes that frequency not come up after geneator start.
9/8/2016 5:14 PM
Thank you sir can any electrical appliances causes low voltage from thecgenerator