How to protect an electric winch from excessive work rate?

[Andres9292]

I am designing a dumbwaiter that will be used to transport food supplies 6 meters vertically into a third floor. Im planning to use an electric winch to do this. However, the winch has a work rate of 20% at 10 mins, so its able to work for 2 mins before having to rest 8 mins. It takes 36 secs for the dumbwaiter to reach the 3rd floor so if it makes 2 trips it will take 2 mins 24 secs. However, the end user might have to make up to 25 trips to get all the supplies they need into the 3rd floor, so besides warning them about the appropriate use of the dumbwaiter I would also like to have some sort of protection to prevent overheating of the winch. The winch consumes 7.72 amps, so my idea at the moment is having a 5 amp MCB with a type D trip curve, but i havent been able to find the exact time when the breaker would trip because all the trip curves i find online vary and it just seems that doing this wont be reliable or precise enough. Is there a different way to protect the winch from overheating?

Thanks

P.S. alternatively, ive heard theres a different type of electric winch that has a higher work rate but cant seem to find it, do you guys know how its called? I need one that has 440 lbs rating with a single line configuration

 

[LittleInch]

Why don't you just buy one from someone like this.

https://www.stannahlifts.co.uk/products/service-goods-lifts/dumbwaiter

If you really want to build your own then you need a proper motor.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[EdStainless]

First I would look at force cooling the winch motor with a fan. Have it set up to turn on when the winch comes on and to run for a couple of min after it turns off.

There are a bunch that are 50% or so

https://www.etrailer.com/Trailer-Winch/Master-Lock/2953AT.html

look for garage hoists or trailer winches since you don't need a lot of lift.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[waross]

You can forget that winch and install a suitable winch now, or you can wait until your customer toasts that winch and then install a suitable winch.
It shouldn't take more than a few days for that winch to smoke.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[MacGyverS2000]

If a designer told me I have to wait 8 minutes before I can use the product again, I'd fire them on the spot and find someone who would install a proper continuous-duty motor. Any other "solution" is silly.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[LittleInch]

The problem with your initial thoughts though are that you don't seem to allow any time for the people to load and unload the waiter.

If it takes 30 odd seconds to make the journey, then simply add in a 2 minute timer before they can press the button to lower it again. Two minutes should be a good enough time??

That time is probably based on max load / current flow so if on the way down it's very low load then you won't need to wait as long.

Also are you using a counter balance system to reduce load (basically a bit less than the static weight)? If not why not?

The fan idea will reduce the time as well.

But this does sound very DIY?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[itsmoked]

Twenty five trips.. Would represent one hour of enforced waiting.

Picture people using an elevator having to stand around waiting for its rest period to end.

Not acceptable.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[jraef]

Whatever you do, don't protect it by using something like an MCB, other than as a last resort. Breakers are not meant to be limiters, they are protective devices, so they have a finite number of operations they are good for, based on supposedly NOT having to operate except in emergencies. Also, making someone reset a breaker will result in someone coming up with a way to get around that "annoyance", it's human nature.

The way to do this is, as LittleInch indicated, restrict the control / call circuit. Let them push the button all they like, but have a timer set up to disallow operation beyond the limits of the equipment. Personally, I would do this with a little "smart relay" / Micro PLC, but that might be a little much for the uninitiated. You can get simplistic timers to to that too.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[waross]

Never underestimate the ability of the customer to thwart a safety timer.
My worst experience was a safety mandated purge timer in a refinery.
A creative operator trying to bypass the purge cycle managed to find a program bug that shut the process down and left it down.
I was in Vancouver Canada when I got a frantic call from a refinery in Toronto.
Help, a heater went down and now the controls are locked.
If you put a timer on that hoist the majority of customers or their pet hotshot will disable it.
The rest of them will demand that you change it.
The winch is too light.
Buy or design a better one.

Bill
--------------------
"Why not the best?"
Jimmy Carter