Colour Roll With Three Phase

[RobOwen]

Hi,

I've used the search and can't find anything on the subject.

I have just put up a camera system in a showroom/warehouse outfit and I am having some problems with some of the cameras. The premises have three phase power and use Florescent tubes for lighting. In the main showroom the lighting is split across the three phases. On the screen (local or at the DVR) for the showroom cameras I get a yellowing over the first phase of lights, which gradually fades to the second phase, and then to the third. Sometimes the fades are quick, other times it is slow. If only one set of lights are turned on (the other phases turned off) then the problem does not occur. At some point in the cycle the image is perfect. There are multiple cameras in the showroom and the fading between the colours is consistent across all of them.

Is there a way of solving this problem?

The PSUs are located in the main office and have their own supply, but it obviously isn't possible to get them on the same phase as the lights.

I thank you in advance.

Robert Owen

[miaren]

I would try a Humbug device (Isolation Transformers), available from all good cctv suppliers, as this is used to cure ground loop faults.

With the PSU's, are they the "Soap-on-a-Rope" style? Could it be worth trying the grounding of the 0V to earth? I have measured over 90Vac between the PSU o/p's and earth. I dont know if this will help but it might be worth trying?

[RobOwen]

The PSUs are wall mountable cabinets. Four outputs (via screw terminals) rated at one amp. We have three enclosures next to eachother, powering twelve cameras.

I will have a go at puting the 0V to earth. Do you think this will cause the camera to sync with all three phases?

[miaren]

I can't see how a camera will sync with 3 phases.

By linking the PSU's 0V to earth will give them an equal reference to earth - if the problem is earth-related of course.

I can't say this will work but I would try it myself.

It would be interesting to know if the Humbug changes anything?

[RobOwen]

Its got to be worth a shot.

I will keep you posted.

Thanks for the advice, its appreciated.

[SUBS]

If they are matal boxed PSUs, you'll probably find that the 0V is already earthed.

Try lifting temporarily disconnecting the mains earths to all of them them and see what happens. not usually a problem if the monitoring kit is near to, and powered by the same mains though.

Worth a try if you think its a hum problem....I'm not sure it is.

have you tried turning the lights off and looking at the pictures in daylight ?

[Baracus]

Change all the lights to High Frequency

[james.wilson]

or increase the shutter speed on the cams

[RobOwen]

Hi, Thanks for all the replies.

The cameras are fine in normal daylight, and when only one set of lights are on. The problem occurs when two sets of lights from different phases are on.

The build is new, and all the lights are brand new so changing them to high frequency would be a problem. The shutter speed is automatic, with no adjustment on it, supposedly 1/50 - 1/100,000.

Does this mean the cameras need replacing to higher spec, with manual shutter adjustment?

[miaren]

or increase the shutter speed on the cams

Yeah, good point, could be the difference in frequency of the lights..

Could in be the three phases aren't balanced with equal load??? (just a guess, i'm not a sparky)