What would be the maximum current during startup on a circuit with 60 x 58W fluorescent tubes?
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Startup current on fluorescent tubes
- Thread starter lumphammer
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electronic or regular ballast?
according to one source I found..
non-compensated ferromagnetic ballast - 10-15 x In for 5-10ms
compensated ferromagnetic ballast - 20-60 x In for 0.5-1ms
electronic ballast 30-100 x In for 0.5ms
also, is that a single tube pre fitting?
according to one source I found..
non-compensated ferromagnetic ballast - 10-15 x In for 5-10ms
compensated ferromagnetic ballast - 20-60 x In for 0.5-1ms
electronic ballast 30-100 x In for 0.5ms
also, is that a single tube pre fitting?
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The fluorescent lamp either uses a ballast of some sort or a switched mode power supply. Both have an inrush typically 5 times the normal operating current for ballast and up to 40 times normal operation current with a switched mode control often referred to as electronic ballast. This is normally completed within one half cycle it may take a full cycle i.e. 20ms. However the use of power thermistors can reduce this inrush peak value and spread it over a longer time.
Also the impedance of the circuit can affect how it works will multiple lamps and here we start to look a transmission line theory which is complex.
For this reason it is common to use a switch panel as most humans can’t operate the switches within 20ms of each other so this works well.
I used a string of 25 units to light tunnels supplied with a 16A MCB at 110 volt each unit rated at 60W. The MCB held to start with then tripped and we realised they used over the 0.6A we had allowed so we changed the tapping on first 20 fittings to 127 volt instead of 110 volt and they worked well. I had no problem with tripping on first switch on. But it may have been old loadmaster MCB but to date I have not had any problems with inrush on fluorescent lamps even when all were HF type.
Sorry can’t really help more. As far as I am aware the only problem inrush has caused is with electronic switching e.g. dimming units. Only cure is to fuse with semi-conductor fuses as although you may get manufactures data when designing a system you must allow for the replacement with a different manufacturers product so not really much help.
Edited to correct maths
Also the impedance of the circuit can affect how it works will multiple lamps and here we start to look a transmission line theory which is complex.
For this reason it is common to use a switch panel as most humans can’t operate the switches within 20ms of each other so this works well.
I used a string of 25 units to light tunnels supplied with a 16A MCB at 110 volt each unit rated at 60W. The MCB held to start with then tripped and we realised they used over the 0.6A we had allowed so we changed the tapping on first 20 fittings to 127 volt instead of 110 volt and they worked well. I had no problem with tripping on first switch on. But it may have been old loadmaster MCB but to date I have not had any problems with inrush on fluorescent lamps even when all were HF type.
Sorry can’t really help more. As far as I am aware the only problem inrush has caused is with electronic switching e.g. dimming units. Only cure is to fuse with semi-conductor fuses as although you may get manufactures data when designing a system you must allow for the replacement with a different manufacturers product so not really much help.
Edited to correct maths
Providing you use X rated switches and type C MCBs, there should be no problems with inrush current.
what maths course did you do at school?? 
50Hz is 50 cycles a second..
so that's 1/50 = 0.02s per cycle... that's 20ms in my book?
50Hz is 50 cycles a second..
so that's 1/50 = 0.02s per cycle... that's 20ms in my book?
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Yep my mistake. Had it in back of mind RCD tripped within one cycle and obviously it has to trip in 2 cycles I did not work it out.what maths course did you do at school??
50Hz is 50 cycles a second..
so that's 1/50 = 0.02s per cycle... that's 20ms in my book?
School was a long time ago. I left couple of years after we started to use earth's on lights.
there was always earths on lights... the gas was fed in metal pipes wasn't it? 
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Yes but so hard to retro fit. I only remember them in a caravan not only a better light but also kept caravan warm.
Of course the old tungsten lamp also helped to keep the house warm and delayed the lighting of fires or in later years switching on of central heating by a good month as Autumn approached.
But the tiny minds of government can't seem to work out the difference between a large office with lights on summer and winter alike to a small house where the lights are mainly used at night when it is cold and we need the heat they produce.
I phoned the energy saving trust and asked them how much energy they save when the reduction in central heating cost is taken into account.
They say they have not done a study on that and admit with a house with a lot of air changes because the light bulb produces radiated heat which means the people and furniture is heated rather than the air it could work out cheaper than using central heating but they think with a normal house using energy saving bulbs will save energy. In other words they don't know and the guy at end of phone is guessing?
However can't see how all this will affect inrush. I have heard that the increased use of switch mode power supplies which only use the peaks of the supply is altering the AC wave form and reducing the peak voltage even though the RMS value is still within speck and this could adversely effect our electric bills. In the past there were loads of star/delta and DOL motors which would maintain the wave form but even motors are being now run on switch mode inverters.
Oh what a tangled web we weave?
Of course the old tungsten lamp also helped to keep the house warm and delayed the lighting of fires or in later years switching on of central heating by a good month as Autumn approached.
But the tiny minds of government can't seem to work out the difference between a large office with lights on summer and winter alike to a small house where the lights are mainly used at night when it is cold and we need the heat they produce.
I phoned the energy saving trust and asked them how much energy they save when the reduction in central heating cost is taken into account.
They say they have not done a study on that and admit with a house with a lot of air changes because the light bulb produces radiated heat which means the people and furniture is heated rather than the air it could work out cheaper than using central heating but they think with a normal house using energy saving bulbs will save energy. In other words they don't know and the guy at end of phone is guessing?
However can't see how all this will affect inrush. I have heard that the increased use of switch mode power supplies which only use the peaks of the supply is altering the AC wave form and reducing the peak voltage even though the RMS value is still within speck and this could adversely effect our electric bills. In the past there were loads of star/delta and DOL motors which would maintain the wave form but even motors are being now run on switch mode inverters.
Oh what a tangled web we weave?
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