Fluorescent lamp load calculations

[jojo]

Hello.. Need your help regarding fluorescent lamp calculations. Lately, I've encountered problems regarding the load calculations and on the actual current/meter readings. The actual current reading is very high compared to the calculated values. Usually, when I calculate fluorescent loads what I would do is to check the lighting manufacturer ballast catalog, then I use the Input Watts (not the lamp rating). In the catalog, there's also a column for 'mains current during normal operation mA'. Sometimes I noticed that there's a difference in watts calculation if we're to use the current column. Example: for an 18W 220V/60Hz lamp, in the catalog the input power watts is 28, power factor of 0.85. In the 'mains current during operation' the current is 0.352A. If I'm going to use the current, the watts will be different (watts = 0.352A x 220V x 0.85 = 65.8 watts).

 

[steve66]

Hello.. Need your help regarding fluorescent lamp calculations. Lately, I've encountered problems regarding the load calculations and on the actual current/meter readings. The actual current reading is very high compared to the calculated values. Usually, when I calculate fluorescent loads what I would do is to check the lighting manufacturer ballast catalog, then I use the Input Watts (not the lamp rating). In the catalog, there's also a column for 'mains current during normal operation mA'. Sometimes I noticed that there's a difference in watts calculation if we're to use the current column. Example: for an 18W 220V/60Hz lamp, in the catalog the input power watts is 28, power factor of 0.85. In the 'mains current during operation' the current is 0.352A. If I'm going to use the current, the watts will be different (watts = 0.352A x 220V x 0.85 = 65.8 watts).

To calculate the load on a branch circuit, you want to use the ballast input current. That takes into account both ballast losses and ballasts that overdrive lamps. It also takes into account the difference between Volt-Amps and Watts.

Volt-Amps include reactive power. That's power that is sent to the ballast on part of a cycle, and returned to the source on another part of the cycle. But it results in a real, measurable current flow. That's why the power you calculate using the input amps is higher than the listed ballast wattage. Its also related to the power factor of the ballast.

However, .352 amps at 220V seems extremely high for a ballast driving an 18 watt lamp.

 

[jojo]

thanks for sharing steve66. I'll use the ballast input current in calculating the branch circuit ballasted loads.

 

[jumper]

Are your specs coming from something like this?

http://www.ecat.lighting.philips.co...cfl-pl-t-pl-s-and-pl-c-lamps/913710121850_eu/

 

[jojo]

Yes, jumper. That's it..

 

[jumper]

I am tired and it is late here, but something about the specs and info on that page seems wrong to me. The .325A on the ballast seems high, as was stated earlier. I am missing something.

 

[jojo]

thanks jumper. it's okay.. i used the input power watts column from that spec in load calculations.

 

[jumper]

Where in the Philippines are you located? Just curious.

 

[jojo]

In Manila.. i think it's 3AM there.

 

[jumper]

Are the electrical codes there based on the NEC or IEC?

 

[jojo]

Our national electrical code here is based/referenced on the NEC.

The nominal voltage we use here for devices/equipment is 230V for single-phase. This includes the receptacle loads, lighting loads.. For larger loads especially 3-phase loads (and for industrial plants) we use 400 or 480 volts; it depends on where the equipment is purchased like in US or in Europe. So some are using IEC, some are using NEC.

For commercial electrical systems others may be using delta-delta system, while others is using the delta-wye system.