# Reversing soft start for freezer crane



## Mbit (Feb 28, 2020)

Let me know if this is even possible

I've got a bunch of cranes in a couple of -30 freezers that are snapping gears like crazy and the company went out of business quite a while ago so parts are not easy to get.

The crane has:

4 travel motors that move at the same time to move the entire crane on the gantry.
440VAC ungrounded system (isolation transformers?)
120VAC control power
1 speed
Forward and Reversing contactors
Radio control
All the controls ride on the crane it only has power traveling with it.
-30 farenheit in the freezer


I would like to basically just remove the Fwd and Reverse contactors and overload if I can find a drive with that functionality. The controls are just simple dry contacts from the radio control cabinet.

I am googling to the best of my ability out here but I'm extremely limited on bandwitdth unfortunately. So if anybody has any suggestions I'm open thanks.


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## Mbit (Feb 28, 2020)

Ok so after doing some research it appears that a soft start is a no go.


The amount of starts/stops could be in the hundreds and there aren't any I've found that could handle that. So it will have to be VFD.


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## 460 Delta (May 9, 2018)

How about a simple, old fashioned iron core reactor in between the line and the contactors? A few turns of wire on an iron core will take out the current spike and smooth out the motor start, at the expense of start torque of course.


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## varmit (Apr 19, 2009)

VFDs would be the way to do this. Be sure to get VFDs rated for crane/hoist service. Also, the ungrounded system will limit your options on the drives,
as many brands can only be used on a wye system.

You should also check on the drive suitability for -30 F use.


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## Mbit (Feb 28, 2020)

460 Delta said:


> How about a simple, old fashioned iron core reactor in between the line and the contactors? A few turns of wire on an iron core will take out the current spike and smooth out the motor start, at the expense of start torque of course.



Ok I will look into this. I was thinking a drive would still give me close to full starting torque. When the cranes are working it's non stop for 12 to 18 hours. As it is right now there's a lot of bumping to get it perfectly lined up over the load and it's hell on these old cranes.


https://www.alliedelec.com/product/eaton-cutlerhammer/de1-34011nn-n20n/70799613/


This one would actually meet all of my needs assuming it can handle the abuse. I want to install a bypass so if it blows I can just flip a switch and continue as normal.


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## paulengr (Oct 8, 2017)

First off as mentioned watch out for temperature limits on ALL electronics. All component values change with temperature and you are well outside the normal industrial limits.

Second crane rated VFDs are for hoists in particular. Travel motors don’t have the same safety requirements. The biggest advantage of having both is if you use anti-sway. With anti-sway when the crane stops it has a way of doing a quick reverse motion to stop the load from swinging. It reverses direction to take the pendulum swing out of it. If you watch the load, it just dead stops. If you watch the traveler it does a “shimmy” as it stops. This little trick can significantly improve performance (more production) if you have swaying loads.

Third, watch out for complaints about how it will be “slow”. Contactor only cranes literally skid on the rails, something you do not want to do if you can avoid it.

There are two kinds of soft starts, continuous duty and bypass style. As implied continuous duty would be no problem. But these can’t actually reverse so you’d still need reversing contactors. You’d just insert the soft start in series. If you are looking at the Cutler Hammer ones, they are grossly undersized. They are the smallest soft starts in the industry but they don’t last very long.

One VFD can drive all 4 motors if you run it open loop (V/Hz mode) with overloads on each motor individually. Performance will be limited. Otherwise if you truly want torque control (V/Hz will be current limiting only), run in flux vector mode with four drives load sharing. Crane drives most likely will require encoders and you have to find some place to mount them but will be full vector mode.

If none of this makes sense don’t just start sticking VFDs in and guessing. Motion control which is what you are doing is pretty advanced.


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## paulengr (Oct 8, 2017)

Mbit said:


> Ok I will look into this. I was thinking a drive would still give me close to full starting torque. When the cranes are working it's non stop for 12 to 18 hours. As it is right now there's a lot of bumping to get it perfectly lined up over the load and it's hell on these old cranes.
> 
> 
> https://www.alliedelec.com/product/eaton-cutlerhammer/de1-34011nn-n20n/70799613/
> ...



You need more than a bypass. A “bypass” is a three contactor or in your case 4 contactor system. The drive gets two contactors to isolate both sides. The other two are reversing contactors. BUT many VFDs fail prematurely doing this because the precharge circuit can’t take getting hammered.

But that drive won’t work for several reasons but the biggest one is that unless you have a strange crane I’ve never seen, it plugs the motors for switching directions so the motors are also breaks. That VFD is a two quadrant VFD only with a diode front end. The moment you try to reverse directions in the crane it will trip out on bus overvoltage if you are lucky, or explode. You need a four quadrant drive and many cranes also need a brake chopper and resistors too.

This is one situation where you need to call KKI or Demag and eat the fairly high cost of letting them spec everything out and install it. Even if you bought the right drive which costs 300-400% more than that CH drive it’s well worth someone who knows all the gotchas and headaches dealing with it.


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## JRaef (Mar 23, 2009)

Mbit said:


> Ok I will look into this. I was thinking a drive would still give me close to full starting torque. When the cranes are working it's non stop for 12 to 18 hours. As it is right now there's a lot of bumping to get it perfectly lined up over the load and it's hell on these old cranes.
> 
> https://www.alliedelec.com/product/eaton-cutlerhammer/de1-34011nn-n20n/70799613/
> 
> This one would actually meet all of my needs assuming it can handle the abuse. I want to install a bypass so if it blows I can just flip a switch and continue as normal.


Won't work (at least not for long). European design, not suitable for connection to a Delta power system, Wye only. It's not evident in the brochure, you don't find out until you read the manual...



> DE1 variable speed starters can be connected to and run on all *neutral point grounded AC supply systems* ...


 This is typical for all VFDs made primarily for overseas markets, where they don't use Delta power systems. US based drive mfrs, like Allen Bradley, provide options for connecting their drives to Delta systems by removing internal ground reference points and using components rated for 480V L-G, not 480V L-L but 277V L-G as the others do. 

Find a PowerFlex 523 drive and remove the "jumper" (ground reference connection) per instructions.

You will need a space heater inside of the box, and I would insulate it. The A-B VFD is rated for -20C, but that is only -4F (the Eaton one is only -10C / +14F).


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## paulengr (Oct 8, 2017)

That AB drive is made in Korea, not US either. Their MV drives are made in Cambridge, Canada with Korean parts. Contactors in Poland. Only thing American about AB is the clock tower.


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## Mbit (Feb 28, 2020)

JRaef said:


> Won't work (at least not for long). European design, not suitable for connection to a Delta power system, Wye only. It's not evident in the brochure, you don't find out until you read the manual...
> 
> This is typical for all VFDs made primarily for overseas markets, where they don't use Delta power systems. US based drive mfrs, like Allen Bradley, provide options for connecting their drives to Delta systems by removing internal ground reference points and using components rated for 480V L-G, not 480V L-L but 277V L-G as the others do.
> 
> ...



Ok researching Powerflex 523. 



They had problems before with condensation in the enclosures when they put heaters in and ripped them out, supposedly. Sometimes the freezers are on sometimes not so big temp swings. I'm thinking if I insulate them it will be too hot when the freezers are off in the summer 



We are "IT" as the IEC calls it not delta


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## CoolWill (Jan 5, 2019)

Put a heater in the electronics cabinet and gear box? A 10 watt appliance light bulb?


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## MOA (Mar 12, 2008)

You may want to look into the alignment of those "old cranes". You could be chasing a mechanical problem with a electrical solution. The contactors over the years may have been replaced down to a size inadequate to function reliably. One motor not pulling its weight on a 4 motor base crane will stress all gearing. Good luck


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## paulengr (Oct 8, 2017)

MOA said:


> You may want to look into the alignment of those "old cranes". You could be chasing a mechanical problem with a electrical solution. The contactors over the years may have been replaced down to a size inadequate to function reliably. One motor not pulling its weight on a 4 motor base crane will stress all gearing. Good luck



If it's that old don't forget when the rails are so roughed up that it gets caught on the pitted rails, to say nothing of worn out wheels and bearings. Personally I have done crane upgrades before. I sold the electrical on the huge maintenance cost of constantly replacing contact tips and parts on those multispeed contactors. I sold the crane repairs on simply paying the crane company to come out and do a mechanical evaluation. By the time they got done they made it sound like we were lucky the thing didn't just collapse and fall to the floor. Which was actually true because the rail supports at one end were actually moving and collapsing under it. By the time we got done the only thing that was original was the frame itself.


Mind you this was in Griffin Pipe in Florence, NJ, a plant that had been in operation for over 200 years! The cranes dated back to the 1970's or perhaps earlier, and were pushing 40 years when I had to deal with them.


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## Mbit (Feb 28, 2020)

Yes they are 30-40 years old. We are in beginning stages of having new cranes designed and built. I'm trying to get us by until then as it might be up to a a year. Everything electrically is basically as it was when built, everything is replaced like for like.


They actually have some type of thyristor soft start on them as OEM from the 80's but they don't work anymore and they've gone 'round and 'round trying to adjust them (there's only 2 dials with a couple detents each) and can't get them to actually do anything.


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## MOA (Mar 12, 2008)

These units have seen 40yr's of use. Some form of reduced voltage starting and creative wiring may be sufficient to limp these things home. Star/Delta,Resistive? Any chance of rebuilding those thyristor units? They were obviously built like tanks. Grab a cheap softstarter wire it in and hammer it. Who knows You may be surprised. If all else fails, load up on a years worth of gears, You may get a bulk deal. Good luck.


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