Duty cycle

[drg]

Today there was a post with duty cycle in reference to a light bulb problem....

I never heard the term duty cycle applied to any thing other than a welder .......

In article 100 definitions there are several references to "duty" and they all seem that the term "duty" simply means a time duration of use.

In my lincoln welders guide for my home welder ( which took me forever to locate) it has the term DUTY CYCLE :
The 60Hz welders are rated 20 % duty cycle and the 50 Hz welders are rated 15 % on all switch positions.
THIS UNIT IS A AC /DC- DC+ WELDER.
Duty cycle is based on a ten minute period. This means that the arc can be drawn for 2 minutes out of each 10 minute period ( with a 20 % duty cycle unit) without any danger of overheating.
If the welder is used for more than 2 minutes during several successive ten minute periods, it may overheat.

So from what I am reading and understanding "is it proper" to use the term "duty cycle" in a broad sense for a time duration of electrical use ??

I do not go to any schools, so other than what I pick up at work and here on this forum, I'm trying to self learn from books at home , sometimes there are certain questions that i will not ask at work for various reasons so any help that comes from here is appreciated .

John

 

[richwaskowitz]

Re: Duty cycle

Sorry for the cornfuzion. But when I said "duty cycle", I was alluding to the relatively long time during each day that these lamps were lit (dusk to dawn). It is probably not the textbook definition, but when speaking of a dewvice with a continuous cycle and the length of time something is turned on in comparison to the time it is turned off I thought everyone would understand me. What I should ave said was "they are on for over 12 hours a day in the winter and rack up lots of hours in a few months" compared to the scone lights that are only on when I turn them on.

 

[charlie b]

Re: Duty cycle

To my way of thinking, the important word in the phrase ?duty cycle? is the second word. ?Cycle? means on once, and off once. I do know that the more frequently you turn a light on and off, the sooner it will fail. Leaving it on for 12 continuous hours, then off for 12 hours (one ?duty cycle?), is less of a strain than turning it on for 1/2 hour and off for 1/2 hour over the same 24 hour period (24 ?duty cycles?).

 

[stew]

Re: Duty cycle

Hey someone who actually reads his service manual !! what a novel idea. I sold Lincoln products for many years and that one issue was what caused many a welder failure. They just could not understand whay when they used thier little ac 225 and weld 1/8 low hydrogen electrode at 130 or 140 amps for hours on end why the smoke came out of the machine. Try as we might we couldnt put the smoke back in so they would have to but a new unit. Thats when they started to read the manual!!

[ March 11, 2004, 05:58 PM: Message edited by: stew ]

 

[drg]

Re: Duty cycle

Stew I have been reading article 630 and article 100 definitions all day in reference to the term duty, I have smoke coming out my ears......this has helped to understand terms used and why, besides all that I want to ask you if you have a 20 % duty cycle lincoln welder can you run it longer outside ....lets say its 20 degrees outside and windy would it be ok to weld for 6 minutes and then wait 4 ???? Something on that order.

Thats what I have been doing and always wondered if this bad reasoning..... have also built a wooden under carriage so it is off the ground 8" and the center is cored out to allow air flow thinking that this will help.

I had to hardface a small backhoe bucket with this unit and it took me days to complete because I followed the instructions in the manual and did not want to burn up the welder.

John

 

[stew]

Re: Duty cycle

you are correct in your reasoning that a lower ambient temp would help. the duty cyle is generally expressed at room temperature. I know thats a bit subjective but thats how it is done. No real way to tell how 20 deg ambient would affect the machine except to say that the lowered ambient would definatly give a higher duty cycle but how high would just be speculation. If you can smell it its too hot. Afraid if you were welding for any lenght of time however the welding smoke would meld with the winding smoke and you mite not know until its too late.

 

[stew]

Re: Duty cycle

also glad you cored out the bottom because there is a grill on the botttom to allow air to flow!!

 

[iwire]

Re: Duty cycle

John it's been a while since I have read welder directions but I believe that 20% duty cycle is at full current.

Set the welder back to a "normal" heat setting and the duty cycle increases.

Not to say that at 90 amps (if your rig is a 225 amp) you still would not have to rest a bit.

Example: If your rig is rated 225 amp @ 20% duty cycle and you set the current at 112 amps (50% of the 225) the duty cycle will now be 40%.

Check on this before smoke escapes from your machine.

I can not imagine that while you where doing the bucket you where running full current, unless you wanted a bucket more like a sieve.

Bob (Also a direction reader )

 

[drg]

Re: Duty cycle

Bob ,you made a real good point that I never considered, usually the amps are run at 95 when I am hardfacing with 1/8" electrodes.


Now I am going to push the envelope further with this in mind ......

In the mean time I will run at 7 on and 3 off while it is still cool out and keep eye on the unit for overheating signs like smell or smoke.

Have a small loader bucket "1 1/4 yard" that I have to hardface sections and its going to take weeks to repair at the rate im going cause I only put in a few hours at a time on this stuff so any edge will help.

Thanks everyone.
John.

 

[stew]

Re: Duty cycle

i wire you are correct the continous duty cycle of the ac 225 is at the 75 amp setting. If you look at the dial it is circled to stand it out from the other settings,. THis is also the setting that is used for pipe thawing and carbon arc heating/cutting. The factory reccomendation is also to run the welder at no load for 1 hr atfter usuing this setting for long periods to allow the fan to cool the transformer.The calculatiom you have made is your own and not how Lincoln sees it however. It is probably prety close to waht reality is but the factory says that any setting above 75 is 20%. Now as a practical matter I have used these machines without problems weldsing at the 115 and 130 amp settings for longer periods than 20% and have not experienced any problem.

[ March 12, 2004, 08:21 PM: Message edited by: stew ]

 

[drg]

Re: Duty cycle

Stew, ran out to the pole barn and checked ,sure enough a white circle on the 75 amp mark....one question though its on the AC settings..will this still apply to the DC settings??? I think so..well anyways I hope so.

I did not know you could use this unit for pipe thawing......always thought that you had to have a DC generator welder for that..

Ill stick a piece of 1/2" copper tubing outside tonight with water in it and try it on DC (-) and DC(+) tomorrow morning and see if it works, I got to be up a 4 am to work out here anyways so what the heck ill give it a try.
Ill crank the 225 amps on it.

John

 

[drg]

Re: Duty cycle

Originally posted by drg:
Stew, ran out to the pole barn and checked ,sure enough a white circle on the 75 amp mark....one question though its on the AC settings..will this still apply to the DC settings??? I think so..well anyways I hope so.

I did not know you could use this unit for pipe thawing......always thought that you had to have a DC generator welder for that..

Ill stick a piece of 1/2" copper tubing outside tonight with water in it and try it on DC (-) and DC(+) tomorrow morning and see if it works, I got to be up a 4 am to work out here anyways so what the heck ill give it a try.
Ill crank the 75 amps on it.

John

[ March 12, 2004, 08:58 PM: Message edited by: drg ]

 

[iwire]

Re: Duty cycle

Stew thanks for the back up.

The only Lincoln rig I have used was a good sized commercial unit that we would work the heck out of without a second thought.

My calculation was not really my own, my home machine is a 225 Amp unit from Dayton (Graingers) The instructions are long since gone but showed how to figure the duty cycle at various current levels.

 

[stew]

Re: Duty cycle

Yes the circle appies to DC also but dont use the DC for pipe thawing. Lincoln sells a pipe thawing attachment for its DC Industriasl machines also. AC works much better for pipe thawing and is mucuh quicker. Has to do with those electrons runining up and down in a zig zg patern instead of a straight line. !!! The pipe thawing attachment is nothing more tahn a fused terminal board so when you exceed the current rating the fuse blows. They just use a super lag fuse link. On dc as the ice in the line begins to thaw the resistance changes to the dergree that the current actually starts to increase and the fuse will stop any significant spike in current. Kind of neanderthal but it works. Dont use the 225 amp setting either for pipe thawing use the 75 amp setting only on AC only and you wiil see the thawing star almost immediatly.Dont use the dc to thaw pipes it is not anywhwere near as efficient as AC for this purpose.

[ March 12, 2004, 11:53 PM: Message edited by: stew ]

 

[drg]

Re: Duty cycle

Stew, last night I took a 15" long piece of 1/2" copper pipe and plugged one end with a cork and some plumbers putty and filled with water and let freeze over night.....it took about 60 seconds or so before water started dripping out .........

Had the welder at the 75 amp setting .

the pipe was froze solid as it 17 dergees out right now.......

Its good to know that this unit can do this in case on a emergency but will doing this in a house possibly cause damage to anything in the electrical system of the house ??

Probaly some thought(precautions) needed here first before doing something like this right?

I really never had to thaw a frozen pipe and just listened to other people talk about it, now at least im finding out for myself how certain things work instead so just listening to other peoples storys .....which seem to turn out a little different than what really takes place.....live and learn an on to the next thing.

Thanks also
John

 

[stew]

Re: Duty cycle

The electrical system will not sustain any damage that I am aware of. this technique is used widley by a lot of plumbers. Just connect across the pipe and turn on the tap. Then turn on the welder until water begins to thaw .Works like a charm!!

 

[iwire]

Re: Duty cycle

Most times it works fine with no damage to any electrical systems.

I do remember reading in a trade magazine that a crew thawing out pipes underground in a neighborhood with a large welder burnt up the wiring in several houses.

I do not remember how this occurred.

The same type of electric heating can be used to keep supply and return oil lines from underground tanks warm.

This is for commercial boilers that use #6 oil which is to thick to pump cold.