RSW energy consumption calculation

By Amrith_s Date 01-03-2019 20:57

Hi, does anyone know how to calculate the energy (in Watt-hours) of a resistance spot weld application?

What all information would I need to gather. I have the weld schedule, but I don't know how to convert that into power consumption.

Alternatively, is there a reliable method to measure it from the weld timer?

By jwright650 (*****)

Date 01-03-2019 21:38

If I'm thinking about this correctly.....amps x volts = watts; watts x hours = watt-hours
So....using round numbers for easy math: 1200amps x 30volts = 36000watts; 36000watts x 1 minute(1/60 = 0.01667hours) = 600watt-hours

So you need to know the amperage and voltage setting plus the amount of time(in hours) that the welding is taking place.

By 803056

Date 01-04-2019 01:03

I don't claim to be an expert with resistance welders, but the voltage in the secondary is typically on the order of 5 volts +/-. The amperage is rather high and dependent on the nugget diameter and material thickness. The weld time is on the order of a fraction of a second. So the actual power per spot weld is relatively low.

There is a resistance welding handbook that may be helpful available from AWS.

Al

By jwright650 (*****)

Date 01-04-2019 02:24

I forgot about the old AWS handbook manuals...I'll try to remember to look tomorrow when I get back to the office.

By Amrith_s Date 01-04-2019 16:24

Thanks John.

Do weld transformers use single or 3 phase power?

My application is on the order of 150M spots per year, so even if it's small for one spot, it'll add up on that scale.

By jwright650 (*****)

Date 01-04-2019 16:52

I think we may be talking about two different problems.
Are you trying to figure:
-the kWatts-hours that will be consumed by the equipment on the primary side over the course of a year?(like shown on a power bill?)
or - the energy used on the secondary side to actually make the spot weld?

The transformers can be either single or 3Ph, I expect for large commercial type applications that 3Ph power would be the norm.