Duty Cycle

5 on, 5 off. http://en.wikipedia.org/wiki/Duty_cycle

Why they would sugest a max of 5 on, is probably process driven. What's the App?

As Wiki states, which is how I've always understood it concerning equipment, the % of on time in a 10 minute perod. Therefore a 50% duty cycle would equal 5 minutes continuous followed by 5 minutes off. Unfortunately, I cannot go into detail on the application at this time, but yes, it seems to be process driven.

Hello AcesFull

The Duty Cycle limitation on most equipment is caused by the build-up of internal heat in the motor windings.

If you can find a way to remove that excess heat, then the "On" period may be increased over the original design specification of an electric motor.

In earlier years, I have done this, by fitting a water jacket to an ordinary electric motor, when a greater Duty Cycle usage was required, and supplying that motor with a moving flow of refrigerated water.

Care must be taken if you modify a motor in such a way, and if you ever get an electric motor re-wound, ensure that thermoelectric sensors are included into the windings as the rewind job is done.

Then the motor may be very closely monitored, via those sensors embedded into the windings, to ensure it does not become overheated.

Kind Regards....

As Sparkstation said, add the thermocouples to protect the motor, but don't make the mistake I once made, I looked in at the stator as I positioned the thermocouples then I found a convenient location for the cooling spray. It wasn't until after I burned up the motor did I notice that I placed the thermocouples directly under the cooling spray.

Darn, I hate when that happens. Learn from my mistake.

Good luck

At finer point attempt, if I may.

"...build-up of internal heat in...

"...find a way to remove...heat, then the "On" period [can] be increased over the original design spec..."

Counterpoint:

Taking AcesFull's query in rigorous context, might it not be more accurate (at least marginally) to say that, with some form of added heat sinking, the Off-Duty cycle time could be decreased (relative to On-Duty)?

Yes, it's a small distinction, but not one without a difference; and not (necessarily) trivial. Taking the cooling augmentation example given, and assuming it is continuing at constant velocity over motor-on and motor-off cycles, heat dissipation effectiveness would probably not remain likewise constant--this because there would be no heat input during Off-duty.

So, essentially, it could by extension be said, that the duty limit rated for AcesFull's motor is a measure of required off time...(needed) to allow heat dissipation prior to next "heat-input" cycle.

Your thoughts?

I actually measured this "required off time". I wired the motor directly to the main source and thru a switch, bypassing the electronics and ran continuous for 4 hours. This gave me the maximum operating parameters I could expect. It was very consistent too. The motor ran just over 8 minutes on average. Once it reaches the cutoff temp, it then takes 22 minutes on average to cool down within the enclosure. Of course, this was run in lab conditions, not in the field where outside, or if installed inside, the ambient temp may have an impact on the cool down time required.

hi world! I too was a bit confused about duty cycle once. I purchased a new welder, and it has a 30% duty cycle. I wasn't sure just what that meant so I asked my dealer and the way it was explained to me was that a 'cycle' was 60 min., and my welder could weld for 30% of the time, so for every 18 minutes of welding, I had to let the machine cool for 42 minutes. I still am not sure if that 's 100% accurate, but I hope it helps! good luck!!

GenX,

I would suggest further researching that claim, before you burn up your welder. In every welding publication that I have read, many I assure you, duty cyle always refers to welding time in a ten minute period, not 60. It may be time to find another dealer for your welding products and, most of all, advice.

hi IanR, so what you are saying is for every 3 min. of welding, let it cool for 7 min.? I read my manual and it is calling a cycle 20 min. I am not worried about burning it up as mostly I weld small projects and body metal( cars ), most beads only take 5 to 10 secs. with 3 to 4 min. between welds. so I can get 6 min. of straight weld time followed by 14 min. of cooldown time, easy enough.

good day, all!!

It's the time the rod is applied to the work piece relative to the time it's not--the time of welder-unit in welding use, relative to welder in standby (where standby is any time duration in which electrode is separated from workpiece).

If, as has been suggested, welders were to be rated for the time they could (simply) be switched on (powered up) before switching them back off (or unplugging), they would be either be unaffordably expensive (both to buy and to operate), or (at the 30% on cycle rating given) never purchased!

And, from a practical standpoint, how could one ever determine a ratio of switched-on time to switched-off time. Hard to fathom....One could weld a bead all day without stopping, so long as the welder was afterwards turned off for at least three days!

Hello AcesFull,

Yes it means that your motor can be ON during any time Tw interval less than 5 min. Than it should be OFF at least Tw.

Actually, this motor is presumed getting used for short time operations like Open/Close garage gates and etc.

Beyond a doubts you can improve motor's performances the way has been suggested by Sparkstation. But you have to be sure just what you doing. This way you eventually disturb original design and specification so you will be response for any consequences. Isn't it a duty and destiny of truth engineer?

You can replace your motor by other one with more proper duration cycle for your needs.

Good luck.

50% Duty Cycle means 'Maximum timeT' you draw Namplate Maximum Kilowatt-and then you keep running Idle for Another T' till it cools down to prepare for another T' of maximum power service.'

At other load conditions you will observe and plan other time cycles for full work and lean work. What you need to observe is body Temp rise and full-load current in.

Nobody gives a thought to motors -once selected and installed. Thermal overcurrent protection normally is set to do the watchdogging.

Is this motor for Lift/Load/hoist duty?

Thanks for all the answers. Definetely helps. I had the task of validating the operating parameters of the said motor. It is used in a pumping application, mounted within a "water tight" enclosure. The motor has a cutoff device on the coil for overtemp protection. I placed thermocouples, one inside the enclosure to measure ambient temp and 3 on the motor, 1 on the stator, 1 on the top of the coil and 1 on the back of the coil as close to the cutoff device as I could get it. Although I cannot measure the exact temp the coil is getting up to, this gave me a good thermal profile of what is going on during the operation of the unit. I was able to log the data and the conclusion is that it does not meet the spec. This is not due to the motor however, but the "water tight" eclosure which allows for no air movement across the motor for cooling. I then mounted a fan to the rear shaft on the motor and retested. Although this helped a bit, gave a few more cycles before cutting out, which then on average takes 20 minutes to cool, it does not allow for the motor to operate continuously at the recommended operating spec. It looks like I need to modify the enclose to allow for air movement, while still being "water tight". Any suggestions?

<I need to modify the enclose to allow for air movement, while still being "water tight". Any suggestions?>

• Pump outside air into this Water-Tight Compartment. Q depends on motor KW.
• Allow exit of air to atmosphere

Pump/compressor plus piping (watertight) are needed.

Sir:

For heavens sake....design an external forced air ventalation system of that water tight chamber of a flow equal to the volume of the internal motor fan. A small roots blower will give very positive ventalation with minimal heat gain of the presurized air.

Bottom of the well electric pumps are cooled by the pumped water as no air is available but can, with forced air, properly jacketed, be air cooled as in standard designed motors.

Nothing wrong with the motor....just no air flow to let it function as designed.

MR. GUY

I agree. It comes down to cost though. Which is cheaper, a forced air ventilation system for the enclosure, or mounting a larger pump head allowing the same volume to be pumped in a shorter time? We'll see.

Aces Full.........I do not see this as a duty cycle problem..........more like a original design without taking the energy generated heat at energy consumption point..

Two alternatives come to mind.

1. Hydraulic motor powering the pumping the work load at the same location as is now utilized.......elctrical energy for the pump/hydro motor consumed would be by hydro supply pump located out of the process environment in a ventilated ambient air area.

2. External pump location utilizing a venturi type pump (no moving parts) at the processing demand location.......

Simple "off the shelf" controls..........

Properly designed either one could be 100% duty cycle powered actuated at\on the demanded pump output requirements....intermitent or continuous as work load need accommodates.

I see you are located on OC...I am in Whittier...a few miles away @ r1a@aol.com .

Direct contact acceptable if you have further interest.

MR. GUY.

Aces FULL

IF you are talking about motor and in operating parameter mention as 50% duty cycle

simply its means your motor sine-wave should be 50 % on and 50% off nothings Else.

as per my knowledge all motor are design of rated load capacity and run for continues operation.

if some one says 5 minutes and 50% that means function perform by that motor make sufficient but may be some other-factor come in picture in that application and due to safety reason time specified. if so must have time delay / that other factor safety switch in series Else motor burnt out.

Motors have duty cycles starting from S1 to S8. S1 is continuous ie can run under rated voltage and frequency without exceeding the temp. limits over the specified ambient temp for 24hrs ,365 days year after year.S2 -s8describe various intermittent cycles.ref to any std will provide details with explanation.The duty cycle is always mentioned on the name plate which will be helpful in giving answers.To give a clear answer this info is required.

Hello again AcesFull

You did say: <"....Any input is appreciated...."> so here is a bit more input especially for you.

If it's a Duty Cycle you are really interested in, here's one at the left, and as you can clearly see, the cop is in uniform, and on duty.

You can see the Duty Cycle is plainly marked for Police Duty.

The % usage of this particular Police Duty Cycle would vary, and be dependent on Hours Ridden, against Hours Parked or stopped.

Just trying to assist you, my friend, in my normal helpful way....

Kind Regards....

Now that was the answer I was waiting for. Thank you sooooo very much.