24v starters

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RETRAINDAILY

Senior Member
Location
PHX, arizona
Here is the situation

We installed a conveyor system with 15-24v IEC contractors

10 of the contractors are switched only in alarm
5 are switched pretty heavy.

The 5 that are switched fault out allot some times every 15min

They sent out surge protectors, installed them, no help
Changed card from Triac to relay output, no help
Tonight pulled out the break out board and point to point wired the starters.

Oh installed another 240w power supply wired in parallel ,no help

our company stance has been to go 120v

the vendor sent out there programmer and he has disabled the alarms and the operators say the motors just stop now.


NOW my Question is this a programming problem or is there a problem with switching the 24v that heavy?
 

TOOL_5150

Senior Member
Location
bay area, ca
I am guessing that a PLC is controlling this? Quite possibly the output of the PLC isnt enough to engauge and hold the contactor. Maybe you could try going from the output of the PLC to an ice cube relay, then put your 24V source through that to your contactors.

Have you checked the voltage with the contactors engaged? Possibly VD.

~Matt
 

RETRAINDAILY

Senior Member
Location
PHX, arizona
I am guessing that a PLC is controlling this? Quite possibly the output of the PLC isnt enough to engauge and hold the contactor. Maybe you could try going from the output of the PLC to an ice cube relay, then put your 24V source through that to your contactors.

Have you checked the voltage with the contactors engaged? Possibly VD.

~Matt

yes they are PLC controlled

the Panel came with a 240w.24v dc power supply the other week I put a second 240w power supply

last weekend I tore it apart and changed it to a relay card.

we had used the break out blocks with patch cords for the original install
so they blamed that and last night I tore that out and wired straight from the card to the starters. hopefully that fixes it

i pulled out one of the coils and it has a green board on the side the rep called it a "low current coil"

I don't mind tearing it apart every week I get some over time :grin:
But I feel like I am beating a dead horse here with the 24v starters
 

GeorgeB

ElectroHydraulics engineer (retired)
Location
Greenville SC
Occupation
Retired
But I feel like I am beating a dead horse here with the 24v starters
I design and commission industrial hydraulic systems. Many of our customers prefer 24VDC, and other than the forgetting of voltage drop having 5* the effect as at 120, I've not had any problems. Some of these are 100 HP motors at 460.

When I see a 40 amp power supply with #14 or #16 wires, I know voltage will be low ... and #12, unless very multiple, isn't much better.

The nice thing about DC is that there isn't an inrush current. Measure voltage at the coil when powered and tell us what it is.

NOTE ... I'm assuming coil damage, rare with DC since the current doesn't go up with failure to close. IS that your problem, or is it the contacts? If the contacts, can you tell us whose starters you are using, a model that has failed, and the motor being started?
 

RETRAINDAILY

Senior Member
Location
PHX, arizona
I design and commission industrial hydraulic systems. Many of our customers prefer 24VDC, and other than the forgetting of voltage drop having 5* the effect as at 120, I've not had any problems. Some of these are 100 HP motors at 460.

When I see a 40 amp power supply with #14 or #16 wires, I know voltage will be low ... and #12, unless very multiple, isn't much better.

The nice thing about DC is that there isn't an inrush current. Measure voltage at the coil when powered and tell us what it is.

NOTE ... I'm assuming coil damage, rare with DC since the current doesn't go up with failure to close. IS that your problem, or is it the contacts? If the contacts, can you tell us whose starters you are using, a model that has failed, and the motor being started?


with the response I got on this thread I'm thinking its programing

there is one limit switch that sees 60-75 switches a minute that turns the motors on and off

I'm wondering if there is enough time in there?
or
we need to set up with 2 switches
one-on
and
one 2' back -off.
 

TxEngr

Senior Member
Location
North Florida
Although the IEC Eurotrash is not as ?beefy? as NEMA rated equipment, it is sufficient for your application so I don?t suspect the starters. Getting rid of the breadboard may have solved your problem, but if it doesn?t there are a couple of things I would look at. First I would look at the limit switch. The switching frequency suggests that you may be using a proximity type switch. Some control system input cards don?t like the leakage current from proximity style switches and can give false indications. You can add some loading resistors to the input or interposing relays to resolve this problem. Second, the PLC itself probably has a scan rate fast enough to handle your application but you may want to build some first out ?traps? in the logic to see what exactly is taking you out. This could help you narrow down on the problem. Or it could point out a programming issue that wasn?t picked up. Good luck since these problems can be hard to resolve.
 

RETRAINDAILY

Senior Member
Location
PHX, arizona
^Haha at the IEC Eurotrash comment.

What's faulting out exactly? What PLC are you using? What starters?

ab 5/05 controller
ab 190e starters

the system was relay logic from the 70's
the limit switches 5 of them one for each product slide (Whisker type)

I have know idea how long they have been in there but I wounder if the 120 was too hard on them, too run 24v on them.

We priced it 6 times and new switches were out by the time we got the go ahead
 

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Troubleshooting by trial and error is the least effective means, something to be resorted to only after you have exhausted all other methods of finding the problem. In fact, this trial and error method usually results in creating new problems in the testing that you didn't have before!

Step one is always to adequately define the problem.
The 5 that are switched fault out allot some times every 15min

Contactors to not "fault out", they are electrically activated switches. So either it is not the contactor that is "faulting out", or the contactor is not "faulting out", it is failing. Which is it?

There is absolutely nothing wrong with 24VDC controls; it is safer, easier to troubleshoot, less expensive to handle in the automation system and easy to protect. But no control system at any voltage can perform miracles. One operation per second will exceed the mechanical lifespan of ANY contactor in a very short time, they are not really designed to do that. That is 30,000 operations per 8 hour shift; most contactors, including NEMA designs, are expected to last 10,000,000 operations under lab conditions. This kind of duty cycle will exceed that in under 2 years, less if you have more than one 8 hr shift per day. In addition, Relay Outputs on PLC cards have similar mechanical lifespans, you will wear them out just as fast. You may want to consider solid state control for this.

Take the time to define the problem accurately before you start swapping out parts, it will serve you better in the long run.
 

RETRAINDAILY

Senior Member
Location
PHX, arizona
^^yea thats why I was thinking more time so the PLC does not do any thing until the switch has been open for say 3 seconds
or switch to a photo eye that we can dial it some time
now the operators will hold the product back to build up.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Its hard to tell from your description of the problem.

24V starters are fine. That is not the problem.

If the switch you are talking about that cycles 50+ times a minute is indirectly cycling contactors that often, I would not be one bit surprised to see them failing, or for the overloads on them to trip.

By faulted do you mean the contactors overloads are tripping or the contactors are failing?
 

mcclary's electrical

Senior Member
Location
VA
Thanks for ALL the replies

Some people hate the 24v and say it's the problem they talk about saturation
and some love it.:-?





IMHO I think its programing error.

I hate 24 volt contactors because voltage drop affects them badly. I was called to a plant where they had "shredders" that all had a 6' cord on them. They had 10 or so of these machines, all the old ones worked fine, all the new ones worked intermitantly. What I found was, if the machine was plugged straight into the wall, all would work fine. No problem. But if you unplug the machine, and plug it into a 50 or 100' cord, that would cause enough VD on the primary side of the control xfmr, that it would not produce voltage high enough to activat the starters. All the 120 volt machines worked flawlessly, all the 24 volt machines were extremely unpredictable. Sometime the coils would pull starter in, sometimes not.
 

RETRAINDAILY

Senior Member
Location
PHX, arizona
I had to pull out of there for their BIG inspection :mad:
I just got the call to go back tomorrow


But he said
Taking the break-out board out did not help.

So the programmer used the output bit to call for product. No more Alarms

BUT now the motors just stop for no reason. contractors just open up:-?

I'll get there tomorrow and check voltage at the coil but I got 480 watts of power no more then 10' from the starters.
its not the overloads
I'll have to watch and see how the contractors cycle.
 

RETRAINDAILY

Senior Member
Location
PHX, arizona
this panel is 12' long with with 17 drives every thing is working great except for 5 of 15 contractors
the 10 that are not switched work fine.

we added another power supply for the 15 contractors 240w.

it is just the 5 that are switched and they call for product when OPEN


View attachment 4788

now there is two transformers you see the one
and thats the break-out board that I had to DEMO-out
 
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