So which is best, and what's the draw? 5kVA or 3.3kVA 110 Transformer.

[Jaeger_S2k]

I have both and thought the 5kVA would be the better to keep, 2 x 16amp and 1 x 32 amp. The 3.3kVA has just 2 x 16amp.

But my brain isn't working very well at the moment, so wonder if you guys had opinions (well, there's stupid Q. #1)

I've also been trying to work out, or find the answer to what's the idle current draw on a 110 transformer, i.e. Saw and other things plugged to it but not operating, just ready to work. I've been unplugging it when working elsewhere, thinking I'm saving something.

 

[Seadog]

From what I can see a no-load transformer consumes around 3-5% of maximum load power.

 

[Agroshield]

If you happen to have a current clamp meter, take the top of the transformer, clip the meter around the live wire and measure the current draw at idle.

Alternatively, make an extension lead out of three single cores and clip the meter around the wire.

Or one of these:

Digital Wattmeter LCD Energy Meter Electricity Power Meter Socket Electric Tester FR US UK AU BR Measuring Outlet Power Analyzer - AliExpress 1420

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

 

[Redsailor]

The 3.3 would be ok for most tools, if you needed something like a heavy breaker for concrete then the 5 would be needed. Do you have a socket that takes the 5? If so I'd keep both, use the 5 when needed and the lighter 3.3 for more "delicate" implements.

 

[voipio]

I've just measured the power drawn by a 3kVA autotransformer, with no load connected, and its consuming 33W, with the incoming supply reading 237V and connected to the 240V tap. When the same supply was connected to the 250V tap, the power consumption fell to 28W.

 

[gaz1]

ive kept mine as i have the tools for them

whilst with one i can start the metal chopsaw in and run it a little it soon dies and trips the overload switch

plug it into the other and away its goes

i had a mouthy idiot that thought they knew more than me until he got told to keep out of it as knew nothing it was my tools and i knew what would run with them

the worst part in all this he was using my borrowed 110v transformers who someone else borrowed and was big mouthed on what they knew was best

the look on there face was a story as i went around to collect them from the person who borrowed them

 

[brightspark]

depends on what your plugging in. i have 750w- 1kw [ 2.5kw a 3 kw and a 4 kw pointless humping tyhe bigger ones round as the 1kw does most stuff

 

[Jaeger_S2k]

depends on what your plugging in. i have 750w- 1kw [ 2.5kw a 3 kw and a 4 kw pointless humping tyhe bigger ones round as the 1kw does most stuff

Yeah, the bigger of the 2 is 30kilo.
I think I'll keep it just in case unless I get an offer I can't refuse

Thanks everyone.

 

[Cheesie]

Heavy 9" grinding will trip the 3kva, and if you have a 110 welder you plan ho use on site you will need the 5.5kva, it really depends on the draw of what you intend to use it for, the 5.5 starts to get heavy carrying it up and down stairs or over a muddy site,

 

[Jack Ryan]

I've just measured the power drawn by a 3kVA autotransformer, with no load connected, and its consuming 33W, with the incoming supply reading 237V and connected to the 240V tap. When the same supply was connected to the 250V tap, the power consumption fell to 28W.

That may not be something you are paying for though, it's reactive power.

How does your power utility handle that?

Jack

 

[voipio]

That may not be something you are paying for though, it's reactive power.

How does your power utility handle that?

Jack

You'd have to ask the power and distribution networks collective for a definitive answer on that.

Domestic electricity meters are set up to measure "active energy" so the purely reactive component is typically not measured. The industrial setting is somewhat different, with reactive power taken into consideration, and metered accordingly. However, the 33W and 28W values measured in the above test would most likely arise from the core losses (hysteresis, and eddy current losses), and be picked up by domestic meters. The measured values represent about 1% of the transformer's rated output.

 

[Erie Fred]

Ah yes....^^^ the old "ELI the ICE man" slogan.

 

[Jack Ryan]

You'd have to ask the power and distribution networks collective for a definitive answer on that.

Domestic electricity meters are set up to measure "active energy" so the purely reactive component is typically not measured. The industrial setting is somewhat different, with reactive power taken into consideration, and metered accordingly. However, the 33W and 28W values measured in the above test would most likely arise from the core losses (hysteresis, and eddy current losses), and be picked up by domestic meters. The measured values represent about 1% of the transformer's rated output.

It seems like reactive power is dealt with there, in the same way as it is here - which is what I was asking.

I don't know the characteristics of the transformers you use to get 220V split phase for site work. They are not used here and most likely would not be permitted. The cost of the measured transformer excitation current depends on the ratio of magnetising current to core loss current. If the transformer is current limiting, there will be more magnetising (reactive) current.

Anyway, just curious.

Jack

 

[AdventuresInMetal]

Don't forget almost all portable site transformers have poor duty cycles, that 3.3 kVA is only for 5 minutes with a 15 minute rest period, the continuous rating of most 3.3 kVA transformers is 1.5 to 1.6kVA. A 5kVA transformer is typically rated at about 2.5kVA continuous. Which is about what you want to budget per person in a workshop enviroment. The only exception are "heater transformers" which are significantly more expensive, but plated with a continuous rating and are usually in vented steel enclosures instead of the typical GRP.