Little Lights Flicker

Most likely you have a loose connection somewhere, often times a loose neutral manifests as light flicker.

hi mr jraef,

i forgot to tell you that the light flickers only when the offices are connected to the generator. they dont flicker when the offices are connected to the mains.

i checked all the connections and they were ok.

thanks

Then that would indicate you have a bad neutral connection or a bad bond in the generator circuit somewhere.

Is the mains 50Hz or 60Hz? Are the lights, incandescant or flourescent? I'm not an expert , but I think if the lights are fluorescent, they will flicker, especially if the ballasts are magnetic. Operating a lamp on a lower frequency will cause flicker.

hi mr ronseto,

the mains system is 50HZ, the lights are flourescent screw type.

thanks for your comment but i have question, why the lights are not flickering when they connected to the mains, while the mains is 50hz same as the generator supply.

is there any way to solve this problem without changing the light bulbs?

thanks

Quote Ronseto "Is the mains 50Hz or 60Hz? Are the lights, incandescent or fluorescent? I'm not an expert" yes you are.

Good point. Some people can see fluorescent bulbs flicker at 60 HZ. I am sure you can see them at 50 HZ. If that is the problem you may have to use solid state ballast to eliminate the problem. You may can use a lower temperature bulb if it is fluorescent.

If the lights don't flicker at 50Hz from your normal supply then the lights are not your problem. Don't start changing them.

You need to look to more closely at the generator and in particular what you might be subjecting it to. You mention kVA and amps but there is no mention of power factor although with your load of 26A this is unlikely to be an issue. You might have problems with the sort of load. If you have a heavy computer load or similar with switch mode power supplies you will do terrible things to the wave form from your generator. Likely the mains supply is robust enough to handle it but an 18kVA is only a little diddler of a machine.

How is the generator connected to the offices? Is it through a line switch connected to the main breaker box? Is the load balanced through the breakers? Is there possibly some load other than the office lights, such as a motor for a cooler or refrigerator on the line?

hi mr tom,

the generator cable is connected from the main generator breaker to the ATS, which is located inside the building, the cable come throught a hole in the wall.

there is fridge in there but i already disconnected it when i tried the generator, there is no motors except small toilet exhaust fan and i disconnected it aswel when i tried the generator. and it was the same problem.

the actual load is lights, airconditions and computers with upss.

hi mr txmedic3338

i checked all the connections and i did broke screw using screw driver, just to make sure they are tied.

i am using manual transfer switch to changeover between supplies.

i did make sure that the lights are not flickering when operated on mains.

i did tried one lamp alone from the generator and its flickering. same as when all the offices are on generator.

what i mean with flickering is that its not coming on and off but when i am in the office and looking on the floor, i can notice that the light is not steady, so its little annoying flickering.

the ATS is 100amp three pole, when the mains is on, the generator neutral is not connected and when the generator is connected, the mains neutral is not connected.

i hope i did gave enough information for you

thanks

You didn't mention whether the generator was putting out 50Hz or not...have you checked that yet?

hi mr wal.

yes i had checked it.

when the load was about 26 amps, the generator frequency was 49HZ.

Are you running the entire building on the ATS or just the lights and computers?

hi,

all of the building is running on generator, they are some airconditions, computers with upss and lights.

thanks

hi mr txmedic3338

what i can tell you is that i am the technician, ''i think'' i do repair generators problems, but this is the first time i have same as this problem. i adjusted the stabillity of the AVR and the volts is steady, the frequency is about 49HZ, i tested it with digital frequency meter. when the generator load is 26 amps. the generator is 18.5KVA which can carry about 84 amps as per the name plate. so the actual load is about only 1/3 of the generator capacity.

i was thinking, if the volts is steady and the frequency is steady, why the lights is flickering? is it the sine wave? or maybe because its running by two piston deutz engine! will it be an issue? i mean the turning is not smooth enough?

thanks any way for your help, and sure you will do what you can do.

Quote - 'there are some air conditioners, computers and computers with UPS' and with this list you are wondering why some of the lights are flickering.

This sounds like a very overloaded generator. 18kVA is very small. The loads you have described do not follow nice sine waves. With a horrible power factor your 18kVA could be easily down to 10KW.

Replacing the fluorescent lights with GLS is high up on the stupid list. You need to get rid of load not add to it. This generator needs extra load like a boat needs a hole in its bottom.

Switch all of the load off.

Turn just the lights on. Do the lights still flicker.

Start turning things on like computers, HVAC and stop when the lights flicker.

I can't help thinking a single HVAC unit would flatten this generator but you mention several.

"i did tried one lamp alone from the generator and its flickering. same as when all the offices are on generator"

While you make a good point, that is a lot of reactive load on that little generator, that problem is not only possible explanation.

All valid but probably not the root cause in this instance.

If the OP's measurements are correct then the genset is not overloaded. He also observed the flickering when lighting was the only load.

hi mr silverfox

do you mean need to put more load on the generator to solve this problem?

You mentioned that the lights flickered when they were connected to the generator by themselves?

While you would need an oscope to see exactly how bad, I think that the problem is the waveform that the generator puts out. Many small generators have pretty poor wave forms with a high THD (total harmonic distortion). While it is usually not an issue, some loads are more sensitive to it's effects, The ballast circuitry in those CFLs is usually a very far cry from high quality. Hence they are particulary sensitive to anything less than a perfect waveform. Utility power, on average (in most developed countries), is very clean. A power conditioner could solve your problems. While it obviously is over kill for flouresent lighting, it may not be a bad idea as far as your computer loads are concerned.

hi mr ianR

so i need an other bigger generator to solve it?

why the small ones are poor wave forms? is that the generaor design or its something to do with the engine size?

thanks

Hello Again Electric!

If your full load is 26 amps, and the generator is plated at 18.5 kVA you don't need a bigger (more kVA) generator.

It is good to know you are experienced and have some test equipment.

I still believe the practical approach is you don't need an oscilloscope, unless you have the budget or your boss has the budget to replace the generator, the lights, or both.

Having the oscope might prove the generator is making really dirty power. Now you have a dirty generator and an oscilloscope... and lights that flicker.

That's why I said I don't think you need a scope, as much as you need to answer the question - "Is this flicker problem so bad that we are going to spend lots of money to fix it???"

Here is what all you have done so far that I remember -

Checked and rechecked every connection. Tested with a single light. Tested with all lights and nothing else. Tested with one light and some computers. Tested everything when it was back on the mains.

You've measured the voltage at the source, and the frequency at the source, and it's good to know you are familiar with how to adjust these if needed. 223 volts and 49Hz should not be the source of your problem.

Here are some more things to check ---

What size is the wire you have running from the generator to the ATS connection?

Are you connected 220 Volt 4-wire to the ATS with two hot legs, a neutral, and a ground(earth)?

When the building is running on the generator, are there any 110 - 120 volt loads creating a large imbalance on the neutral? What is the amperage on the neutral?

Have you measured the voltage at the ATS?

Do you have more than 5% voltage drop? When combined with the possibility of "dirty sine wave" power from the generator, this could be anoher cause of your problem.

How is the ground system set up for the building? Earthing Pit, or Driven Rod? Do you know the impedance of the earthing system?

I do not think the 2-cylinder engine is a part of the flicker problem as long as your RPM is constant.

Please tell us what you discover!

TxMedic

hi sir,

thanks for your reply again.

now , to be honest, i did not check the voltage drop, but the 223acv is on the receptacle inside the office when its supplied by the genertor.

there is something i did not inform you about and maybe its an issue.

its single phase generator so i just need two wires from the generator to the ATS box.

i am using 4 core cable size 16mm, i used 2cores together to supply phase and the other 2cores together to supply the neutral.

so its like 2core cable 32mm size.

now, will that do some disturb on the sine wave?

sorry for not letting you know about it from the biginning, i forgot about it.

thanks

Cable arrangement is sound if your description is correct. Is the cable terminated with lugs onto studs or into a screw terminal? Either way check that its all really tight and if there are lugs that they are correctly crimped...check all your cabling terminations while you are at it

Is the circuit for that receptacle (nominated test point) loaded at all?

Can you measure the voltage at the offending lamp(s)? At the distribution board?

Wal and Others - I've been trying to solve this problem by looking at the wiring as the problem, or the fixture as the problem, etc.

What if we could get more information about the age of this machine? I think I read online that the last AEG generators were made in the mid 1990's at the very latest. Is that right, does anyone know? Has another company bought up this division and started making new machines?

And, I'm not familiar with this alternator - is it possible the problem is caused by bad alternator on the machine? Does this type/age of machine have mechanical parts that could simply be worn out in the electrical generation section?

With Electric's (OP) metering equipment he could be easily measuring a steady 223 volts of 49Hz square/step/sawtooth wave trashy spikes?

So - Electric(OP) - can you tell us the age of the machine and the hours on it? Are there any replaceable maintenance parts on the alternator? Electrical parts, filter caps, chokes, filters, anything that could be dead and need repair?

With the two-wire system (one hot one neutral) is there no concern about a common earthing point between the building and the generator?

hi mr wal,

the cables are terminated into a screw terminal at both sides, and i did checked again the tighten. yes they are tight.

when i tested the 223 volts on that receptacle, it was not loaded.

the volts at the lamp holder is 221v, and at the distribution board is 224v.

hope this will help

thanks

That voltage drop seems a little excessive. Maybe...

Have a closer look.

Are these voltages the same whether its genset or utility powered?

So much information but I can't find the type of lights used.

per #6 "the lights are fluorescent screw type."

I interpret that as Edison screw base compact fluoro (CFL)

Thanks.

Interesting?

By the way why not to test an incandescent lamp?

Have you tried replacing the CFLs with regular incandesent lights? Do they flicker too?

Had a similar problem in a bar where the lights had a kind of wavy effect. I found the brewery people had a single phase compressor which had a piston pumping at about 100 rpm so it had a pulsing effect on the local lighting on the same phase.

They fitted a three phase pump and it cured the problem.

So what have you got on this genset as well as the lighting? Have you some HVAC loads or VSDs? Try disconnecting various part of the load. It would not happen with the main grid as it's a lower impedance, cannot drop any volts.

Surely the Genset will have a frequency meter.

Flickering normally is due to low frequency.

That's what I was thinking too but OP says that he measured 49Hz which is good enough really, within the accuracy of the meter anyway.

Has the OP tried speeding up the genset to see if that makes the flickering go away?

A suggestion for a fairly "easy" fix-

Install a UPS system (minimal ride-through battery capacity- 5 minutes Max, 2 minutes better) sized for about 40 amps of service (to give you room to grow) on the output of the transfer switch (so it is fed at all times by either line or generator). If you install with a parallel switching system, you should be able to install without shutting down the site and then initiate it and disconnect the "by-pass" circuit.

This will provide continuous power to ALL devices during an outage- no more rebooting electronic controlled devices and/or computers- while it also guarantees constant frequency output- no light flicker.

Cost should be relatively small compared to the initial cost of the generator, which seems to be a lot bigger than needed.

Since you are the technician- Dismantle the alternator and check that the rotor is not rubbing on the stator laminations. If this is so,check out for bad bearings, cracked banjo or crankshaft-rotor coupling disc causing rotational mis-alignment.

A similar problem showed up recently and was resolved this way!

The problem it seemed from your explanation to be mechanical rather than electrical.

Yes, r4roty2012 you are on to something.

Great job for your first post! I gave you a GA for joining, reading the thread and offering a new and reasonable suggestion to help solve the problem. Great job! There should be a way to award an extra point for someone getting it this good on their first post...

As I told Electric in an off-line note earlier today, I had lunch with our regular generator rescue-mechanic.

He absolutely agrees that this sounds like a mechanical misalignment or even failed bearings allowing the rotor to bang/bounce/rub around in the stator, not just radially but axially as well but to a smaller amount.

Would this age and type of machine have carbon brushes? I forgot to ask about that and have no idea if that's even found on these machines.

Unfortunately for Electric, if any of these issues are the source of the problem, it's going to be difficult or time consuming or expensive to repair.

A good idea but an old experience techi would have easily sensed the malfunctioning Bearigs or rubbing sounds like an experienced driver could feel low pressure or a flat tyre.

Anyhow may be.

You figure that something like this would be audible but then there's a diesel engine running that may well mask the noise of a wobbly armature.

Stethoscope perhaps?

Stethoscope is also one tool for maintenance personnels.

Automotive Stethoscopes are professional tool while normal one can also be used for the purpose.

We in electronics services also use Scalpel, Dental mirror and like and normally included in Tool kits.

A hacksaw blade against your ear works too. You have to get your head close. Careful you don't get tangled up in the works while you are listening though....

Really it works on Growlers not on bearings

But ....the ... works on

How far along is a baby before it gets a heartbeat

even.

Have a fine day!

May be your genset has a one piston diesel engine. Is it 1500 or 3000 rpm? If engine is one piston, small variation of speed (rpm) at each motor firing will occur. This is more notory at 1500 rpm engine. Have experinced simmilar problem at my farm genset with an old Jenbach diesel 1200 rpm. If my theory is right, no way to overcome your flicker, unless you buy a new smooth running genset. Flicker may also be due to rotor uneven gap against stator due to worn bearings. Good luck, Andres

Excellent observation but probably not likely in this case.

From experience 18.5kVA gensets have 3 or 4 cylinder engines and need to put out around 50HP.

Electric already told us it's a two cylinder Duetz diesel in post #26.

I still think it's a mechanical issue or an electrical issue inside the generator because here in the US at 60Hz, the mechanics I talked to on Saturday said the only time they have ever seen this problem with fluorescents it has either been a sync issue, which we have eliminated from possibility, or it's been because of lousy trashy power caused by a bad mechanical fault in the generator. Bad ballasts cause the same problem as they cause on the mains. Bad bulbs go grey and flicker at the ends like they do on the mains.

Between the two, they have around 55 years of generator experience. The Bright Orange Company has billed me for over 20,000 hours of generator run time, so imagine how many hours these guys racked up servicing the sets over the years...

I do wish Electric had a scope.

Electric---have you tried the incandescent bulb? What did that do?

Check the voltage at the lights on gen power.

I had a similar issue and it turned out to be too high of voltage drop. (I was temp powering about 16A of fluorescent lights on a long #14 extension cord).

Removing one fixture from the circuit corrected the issue.

Its possible a loose connection somewhere in the generator circuit is creating a high resistance and causing this volt drop. Just check the voltage at one of the lights that is flickering.

Hope its that simple.

hi all

sorry for this late reply.

i tried all kinds of lights and checked all the connections and the rpm ''HZ'' and the volts, all are ok.

now the owner said its ok if it will not effect the electronic devices, as it will work maybe one hour for one week time.

thats the latest news about this problem

thanks for your help and care

electric