Calculating Watts from Amps

[tsk3009]

Hi all,

 

I am looking to open a small factory in Thailand and I want to make sure the factory I lease can support the initial machinery purchases as well as planned expansion. I know the kW my machinery requires, but all factories list the current or amps available. Assuming a factory with 30 amps and a power factor of 1, what would the  kW output be for a 4-wire Wye circuit (3 phases, a neutral and a ground) and a delta circuit with no neutral? And which of the two is more common in Thailand? Also, the voltage in Thailand for 3-phase power is 400 V, is that correct? Thanks in advance for any help. Cheers!

[Crossy]

A 30A per phase supply @ a nominal 220V is 220*30= 6,600 Watts per phase (19.8kW total). But, assuming a power factor of 1 is unwise unless your equipment is purely heating, 0.8 - 0.9 is much closer to reality. At 0.8 your 30A is 220*30*0.8=5,280W

 

Most of Thailand is 3-phase, 4-wire, 220V phase-neutral, 380V phase-phase. Greater Bangkok (MEA region) is 230/400V.

 

The common supplies are 15/45 (45A per phase) and 30/100 (100A per phase). If you need bigger supplies you are in to private transformer territory. If you are on an industrial estate bigger supplies may be available but you'll need to talk to the estate people.

 

There is no difference between the star and delta configuration as far as power is concerned. If you have 3-phase, 3-wire (380/400V) kit just ignore the neutral.

 

What sort of numbers are you looking at for your supply? A 100A supply is 66kW at a PF of 1.

[tsk3009]

Thank you for the quick and detailed response. I'll need in the vicinity of 100 kW, so at least 150 amps, but 200 would probably be safer. 

 

If I'm looking to lease in the Greater Bangkok area, do you have any recommendations as to whom would be good to contact in terms of finding a leased factory or what parts of Bangkok would be better for setting up a factory? Much thanks.

[Crossy]

What size unit? There are a couple of "instant factory" sites around Rangsit if that's not too far out, but it's not something I've ever looked into so I have no idea of costs.

 

Don't forget lighting and HVAC loads (not a lot of H needed mind). 

 

What are you going to be making?  

[tsk3009]

The unit size I am looking for is fairly small, 1000 sqm or less and for food production.

 

Yeah, I'm not too worried about the heating costs. haha.

[Crossy]

Not a "starter unit" then.

 

This was the first hit on a google seach for "factory leasing bangkok", I have no association with this outfit.

 

https://www.cbre.co.th/en/Services/Industrial

 

By the way, many factory areas are shown in "square Wah", 1 square Wah is 4m² 

 

[tsk3009]

Thanks, Crossy.

[impulse]

Keep in mind that 3 phase power is calculated by Watts = Amps x Volts x 1.732.  That 1.732 is the square root of 3.  That formula applies to any 3 phase motors or other equipment you may be running, like 3 phase welders, etc.

 

Also, KVA (which most transformers are rated for) is Volts x Amps- with the amps being the critical parameter for overheating.  Multiply by 1.732 if it's a 3 phase x-former.  But the KW you pay for are calculated using the power factor.  Sophisticated power companies will ding you for a surcharge if your PF is too low (typically below 0.85 or so).  I'm not sure how they treat a poor PF in Thailand, though.

 

[tsk3009]

Impulse, thanks for the additional info related to the KVA and PF. Much appreciated!

[tsk3009]

I have another question... say I have 300 amps going through the main panel. From there, I have 3 feeder circuits of 100 amps to 3 sub panels, each of which each has all 3 phases and is connected to branch loads. I know that if each phase was directed separately to a sub panel like in residential areas, the power consumption would need to be somewhat balanced among the sub panels because each sub panel has only one phase, but if each sub panel has all three phases, then do I need to use electricity somewhat equally among the sub panels or does it not matter as long as I use the three phases equally from each sub panel?

 

For example, if I use 60 kW (equal amount of all three phases) from sub panel 1, 30 kW (equal amount of all three phases) from sub panel 2 and 10 kW (equal amount of all three phases) from sub panel 3, does it matter that the electricity consumption is different between sub panels? Thanks.

Edited March 30, 2018 by tsk3009

[Crossy]

So long as you don't overload any of your sub-mains you are fine.

 

There is actually nothing to stop you having 3 x 200A sub-mains so long as you don't exceed the total supply capacity of 3 x 300A in operation.

 

Try to keep the phases reasonably in balance but I don't think there are penalties for poor load balancing.

 

If I add up all the breakers in my panel I get a rather scary 348A!! Our incomer (on a 15/45) is 63A, it has never opened.

[tsk3009]

Great. Thanks, Crossy!