Kva

[Farmelectrics]

Kilo volt amp can any one explain why we use this if it =kw any way in other words can someone in simple terms explain kva

 

[telectrix]

power factor. if pf =1, then kva =kw, but when you have a pf of , say, 0.8, then the actual kva is kw/0.8.

 

[Knobhead]

Have a look at How to Convert Watts to VA and KVA to KW Simplified -- Converting Volt-amps to Watts the easy way

 

[Farmelectrics]

thanks for your help lads

 

[Silly Sausage]

VA = sqrt(Watts[SUP]2[/SUP] + VAR[SUP]2[/SUP])

Further reading...

True, Reactive, and Apparent power : POWER FACTOR

 

[Engineer54]

Power factor, when lagging is often termed as ''wattless current''

 

[Knobhead]

Sorry E54, but what do you call leading PF! Wattplus power?

It used to be a favourite trick of mine to get an apprentice to watch the incoming ammeter to a plant as I switched off the PF banks. It would then go on to several hours explaining why the current went up and not down as they expected. It was the best way though, as they had seen it with there own eyes.

 

[Knobhead]

One of them got his mark on me though. “If you ask that, I’ll bet it does the opposite of what I think!”

 

[Engineer54]

Sorry E54, but what do you call leading PF! Wattplus power?

It used to be a favourite trick of mine to get an apprentice to watch the incoming ammeter to a plant as I switched off the PF banks. It would then go on to several hours explaining why the current went up and not down as they expected. It was the best way though, as they had seen it with there own eyes.

I stated lagging, as that is going to be by far, the most commonly seen PF situation... But both are subject to include apparent power.

I would fully accept that switching the PF banks off, would most certainly raise the current, after all that what the capacitor banks are there for, to lower the current flowing in the supply cables!! A lot of it doing no useful work (wattless current).

 

[Knobhead]

I was only joking about wattplus E54!

Try convincing someone that that box sat in the corner that is taking 400A and not doing anything that they can see is actually saving money. I’d rather talk to the doorframe! I’d get more sense out of it!

You and I were taught about it. But be honest with me did you really understand it first off? With new apprentices I found the hands on approach to be the best way to show it in real life.

We’re both singing from the same hymn sheet

 

[Inteificio]

In simplest terms VA is the total power going through the wires, W is the useful power. The ratio of the two is power factor, normally about 97% for most drivers

Everything in a circuit will have impedance, resistance and capacitance at some level. Generally as the error margins in most electrics is so high, it is negligible.
Occasionally it is not, just learn what equipment has a low power factor.

 

[ackbarthestar]

A simple experiment you can do at home

Take one used 58W switch start flourescent lamp place a spsw switch in series with the capacitor. Place a clamp meter around the live incoming conductor and switch on.

Measure the current flowing with the series switch in both positions.