Voltage fluctuation

[Ben Trueblood]

What is the allowable percentage of fluctuation in voltage before it affects the normal operation of the equipment it is feeding? I have 499 V on the line side of the transformer on a 480V system.

Thanks

 

[drbond24]

Depending on the equipment, there will sometimes be a nametag that specifies the range of voltages it will accept. Lighting ballasts come to mind quickly and the ones we have around here are +/- 10%. If there isn't a nametag on it then you'll have to wait for a smarter someone to find their way to your thread.

It may help to specify what equipment is being fed...

 

[don_resqcapt19]

The Illinois Commerce Commission permits the utility to supply to be up to 10% above or below the nominal voltage for all systems that are not supplied at 120 volts.

 

[gar]

080514-2000 EST

Ben Trueblood:

The following discussion has some useful infromation on power quality:
http://my.dteenergy.com/products/customerGeneration/pdfs/electricSystem.pdf

Generally see pages 7 thru 11.


Also look at:
http://www.hydroonenetworks.com/en/...One_Energy_Efficiency_Guide_Power_Quality.pdf


Your over-voltage is only 4% high. At home and my shop we generally run about 123 to 125 V on a nominal 120 V line. Which is about 3.3% high. The house has 240 center tapped, and the shop has 3 phase open delta and a center tapped secondary for the the single phase.

When I design circuits I assume a working range of 95 to 135 V for input. In many factory applications I see the high 120s, like 127.

As drbond24 says check the specifications on your loads. Incandescents burn out quicker on over-voltage. So use 130 bulbs or something more tolerant.

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[mdshunk]

That's 3.9% over nominal. There's no way I'd fret even the least bit about that. I'd call that "perfect".

 

[CAPS]

Most utitlzation equipment is designed to be operated +/- 10% voltage. If in doubt contact the manyfacturer. As far as transformers most power transformers have adjustable taps on the primary side (usually +/- 5%) so that the secondary voltage can be corrected. Loading on the primary side feeder bus may change during the day, and you may not always be at 499v.

 

[quogueelectric]

Does the xformer have a load on it?

 

[csparkrun]

Depending on the equipment, there will sometimes be a nametag that specifies the range of voltages it will accept. Lighting ballasts come to mind quickly and the ones we have around here are +/- 10%. If there isn't a nametag on it then you'll have to wait for a smarter someone to find their way to your thread.

It may help to specify what equipment is being fed...

i agree, nametag and product specs are key, but depending on if you are feeding a panel or equipment would help me decide. i've encountered this while feeding a sub panel at 496v and chose to tap another winding. 10 minutes and peace of mind for the next guy. maybe a good practice or maybe i could have been seeing a spike at that time of day.

 

[gar]

080515-0718 EST

Ben:

Certain loads will have longer life if run at lower input voltage than nominal so long as fluctations to lower yet values do not impair performance. In particular a series pass DC regulated power supply, an incandescent lamp if the lower light level is acceptable, transformers, and induction motors. Both series pass regulators and magnetic core devices will be more efficient, less waste from internal power loss.

Some devices like switching power supplies, and induction motors with constant on-off cycles may give better life on higher than nominal voltage. Switching supplies will run with lower input current at higher input voltage, and motors have better starting torque.

Of course with motors and transformers it is the relationship between core saturation and other performance factors that would define the optimum input voltage for maximum efficiency. There are devices, basically phase shift average voltage regulators, designed for inputs to motors to reduce the input voltage to increase motor efficiency and reduce internal heating. I believe that NASA was the source of this invention.

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