Mh Bulbs

[Joe_P]

Hi Guys,

Curious of the ampere that the various wattage bulb draws...

150 W, 250 and 400W bulbs esp.....

Anyone can help??

[pacificbetta]

Wattage divided by 220V will give you the current draw in amperes. This does not include the power drawn by the ballast, nor the current surge during startup, just current during routine use.

[Ancelot]

anyway the SI unit for wattage is W not V! V is for Voltage!

anyway this is a lesson on physics! haha

[Hon]

According to BLV site,

150watt is running at 1.8amp

250watt is running at 3amp

400watt is running at 4amp

Why you asking? Feeling the pinch from the amp drawn by your 400watter??

[pacificbetta]

I said:

Wattage divided by Voltage equals Current. Plain Power = IV rule.

[Hon]

pacificbetta,

Sala lah....

P = I*E

where I = Current and E = Electromotive Force also known is voltage.

From Ohm’s Law voltage is found by multiplying current and resistance,

E=I*R

Need to go back sch ....brain rusty liao...

[pacificbetta]

Salah?

I thought P = I*I*R, and since V = I*R, then P = I*V

Shit man, if this is wrong, I have speced alot of my designs wrongly liao.

I am getting very confused, I said the same things as you, so why your correct and me salah?

[Hon]

If I'm not mistaken, P = I*I*R, and since V = I*R, then P = I*V.

These formulas only apply for DC circuit ....

AC circuit is not formulated this way....

Oh man...can some electrical gurus step in and help out??

My electrical knowledge return sch 10yr+ ago liao.

By the way, can electrical gurus explain what is phrase angel in electricity?? And also by using a small voltage to chop the sine wave, will the power comsumption be the same before its got chop??

[pacificbetta]

These formulas only apply for DC circuit ....

AC circuit is not formulated this way....

What lao, kena suan liao. Hon, you are wrong, the formula holds also for ac sinusoids. Except that instead of plain I, we use I sinA.

What you want to know about phase angle, I may help? Phase angle refers to "A" above.

And also by using a small voltage to chop the sine wave, will the power comsumption be the same before its got chop??

Don't understand?

[Joe_P]

Darn.... ask a simple question, get a lesson on physics......

[Hon]

pacificbetta,

Looks like you are the gurus uh ...

According to my understanding.

The phase angle control method provides a limited portion of each AC voltage cycle to the load, based on the percentage of power requested. The output is switched on for a portion of every AC half cycle.

So if i run the motor at 100% and motor at 50% speed, is the power comsumptions the same?

Joe_p,

Doesn't you feel fun having a feeling of Back to School???

[pacificbetta]

Looks like you are the gurus uh

Paiseh hor, I also return a lot to sch already. I really do not understand what you are trying to say, possibly using some dc voltage to chop a ac sinusoid thereby controlling the perceived power to some load. The description is too vague. Maybe this weekend at the chalet, you bring paper and pen to the chalet and we scratch our heads together?

I went back to the postings and re read them, I think here is where we drifted apart. Just for the kicks to piss phang a little There should be some NTU EEE 2 or 3yr students here, pls correct me if I go off somewhere here.

ac voltage:

V = VsinA

Because most of or lights and motors represent an inductive load to the power grid, they are represented by Z=R+jL.

The current draw will then by

I = V/Z = [V/sqrt(R^2 + L^2)] * arctan -L/R

The magnitude of the current draw is therefore increase to V/sqrt(R^2 + L^2) if the current is totally uncompensated. However, under optimal compensation, current draw can reduced to V/R. How to do it is to add a suitable capacitor such that the C exactly compensates the L (which was what I assumed was done, hence my reading differed from the BLV specs). It is possible to overcompensate with too large a C and actually increases power consumption. What exact value to use, ask BLV.

[pospeh]

STOP.

You are making my head hurt.

[IanJ]

With the move to higher wattage lamps and more of them per tank, maybe worth a look at HDB guidelines on electrical loads. For the 30 amp main switches, for air-con units they state a max total running current of 5 amps max.

Not sure how that relates to lighting.

[hoppinghippos]

wah I everything also return back to school oredi, but if I"m not wrong, AC current is constant, not sinusoidal, but its voltage is? cuz doesn't make sense for current to fluctuate, since current is the driving force? and I think we don't use V in AC but Vrms? which is Vpeak/ root 2?

[pacificbetta]

Dear all,

I got a few messages on using a capacitive load to compensate for the bulb loading. Rather than exaplinging the same thing a few times over, let me do it once by posting here.

Unfortunately, I caused a few misunderstanding. The correction is being connected on the power grid side. There is nothing much we as end user can do, unless you pretty much have a dedicated power grid. (Just like AT with his 1600W, just kidding)

[boxfish]

Darn.... ask a simple question, get a lesson on physics......

wah lao chio si lang

[Achilles Tang]

Where's Robe when you need him? or Tanzy?

[Tanzy]

Where's Robe when you need him? or Tanzy?

What's there to say? These guys said everything. Anyone wants to talk about nuclear chemistry or mycology?

[Hon]

What's there to say? These guys said everything. Anyone wants to talk about nuclear chemistry or mycology?

the inventor of atomic bomb died recently hor ...h.a.h.ah.

[Fireclown]

I understand from my lecturers that keeping your total current draw on one single power socket below 13A will be safe. Wanna double check on this.

Pacificbetta, you wanna borrow my EEE textbook. Be reminded that it's THICK.

[pacificbetta]

Pacificbetta, you wanna borrow my EEE textbook.  Be reminded that it's THICK. 

Which part of the maths did I go wrong? Need some revision, just in case my boss suddenly ask me something similar.

[supersonic]

Whats the problem with you guys? Just buy the damn SiSir approved lamps and p ay Power supplier.

Why am i even reading this thread.

[Fireclown]

Ah! I'll browse through my textbook and let you know. Pretty confused on what was expressed earlier. Mind to consolidate those stuff? Gotta double check on the phase angle thingy, forgot liao. Hehe

[Joe_P]

Thanks for the comprehensive analytical analysis on electrical wattage and amperes.......

You guys sure know how to complicate issues......

But the reason I'm asking this question is simply cos of the amount of amperes that MH bulbs would drawn, esp during the bulb striking period.... and whwn you have quite a number of bulbs.....

and because I was told that standard wires only runs max 13A and there are 15A wires available ..........

so does 3 x 250W of MH require the higher rating wires...????