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Old December 30th, 2017, 12:35 AM   #1
kalabdel
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Holding brake wiring for hosting application

Hello gentlemen,

I was looking at a wiring diagram of crate stacker that got me curious and compared it to another machine that does similar hoisting and got some questions.


In attached imaged #125 the brake feed comes from a transformer and a safety relay through KB1 (24VDC coil with surge suppressor) which is energized by KIB1 (24VDC coil) which is connected to an Emerson drive. There's also MURR connected to the three phase line before it reaches the brake.

In attached image #126 the holding brake is connected directly to a Lenze drive. I read the manual and couldn't find anything about surge suppression but the drive handles the brake quite well with nor problems that I know of.

If it's any indication of the brake size, the first motor is 4KW and the second is 11KW.

1- Did the first application require that much surge suppression and what would happen if KB1 is connected directly to the drive, skipping KIB1? Remember KB1 has a surge suppressor.

2-What is the MURR suppressor protecting, KB1 or the brake or both?


Thanks
Kal
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File Type: jpg 125.jpg (34.7 KB, 52 views)
File Type: jpg 126.jpg (27.1 KB, 45 views)
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Old December 30th, 2017, 03:44 PM   #2
lpc921
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The image #125 is too unclear to read. It's hard to know the reason without the exact model of the brake. My guess is that the motor/motion in #125 might be safety related. The brake is designed to stop external force in addition to the motor. Looks like a double brake module from the drawing?
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Old December 30th, 2017, 04:12 PM   #3
Highland Controls
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Some drives(KEB S6 for instance) have a dedicated brake output that is rated to directly control the brake(including surge suppression). Most drives do not. They will have a general purpose output that can be configured to control a brake relay.
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Old December 30th, 2017, 05:00 PM   #4
kalabdel
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Thanks a lot. I am attaching a slightly better picture but I don't see anything indicating the brake model and I'm not familiar with a dual holding brake. I will do a search to find out more.
Another thing I noticed is that they used three phase line for the brake in image 125/125A.
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Old January 1st, 2018, 01:42 PM   #5
Gene Bond
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From what I could decipher, it appeared one brake was higher voltage (3ph recified), and another was lower voltage 24vdc or 120vac?

In general, the output relays on drives are ~1a rated, and should not be used for external components like brakes or small motors. They are generally designed as pilot devices for larger relays or contactors.

I see <1a, 24vdc brakes on servo motors run from the built-in relays regularly, although I don't particularly care for the practice...
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Old January 1st, 2018, 03:29 PM   #6
Pete.S.
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I think it's pretty clear.

In the drawing with the emerson drive the brake is a three phase magnetic brake. The inverter drives the first relay which drives the contactor which energizes the brake and releases it.

Without knowing which emerson drive it is, it's very likely that the first relay isn't really needed and the "surge suppression" diodes on the contactor are not needed. I doubt the Murr motor supressor rc-filter is needed too. Overzealous electrical engineer maybe?

In the drawing with the lenze drive you have a motor with a 24VDC magnetic brake. The lenze drives the brake directly. Likely this is fine and the inverter is made for it. You need to check the inverter's electrical installation manual.

There is absolutely NOT a relay on the brake output of any inverter drive. It makes no sense.

It is transistor outputs on everything unless it's explicitly drawn as a relay output connected to three terminals. It's also highly unlikely you need any surge suppression of any kind on transistor outputs because they have that circuitry on the output already build in.

Last edited by Pete.S.; January 1st, 2018 at 03:50 PM.
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Old January 1st, 2018, 04:47 PM   #7
lpc921
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What Pete said makes sense. This is the first time I have seen a three phase brake though. I am keen to learn the model number of this brake if OP can provide.

OP mentioned "safety relay" in the first post so my guess is that the first relay is a safety logic unit. KIB1 is just a input on the safety logic unit. The output from this safety relay drives a three phase contactor to release the brake. The MURR is added to protect against over-voltage due to inductive load.

It's hard to see from the drawing, but is it a dual channel system? Looks like another switching device in series with KB1.
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Old January 1st, 2018, 06:27 PM   #8
Pete.S.
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Quote:
Originally Posted by lpc921 View Post
What Pete said makes sense. This is the first time I have seen a three phase brake though. I am keen to learn the model number of this brake if OP can provide.
3-phase brake is a standard option on larger 3-phase AC induction motors.

Look at ABB for instance https://search-ext.abb.com/library/D...&Action=Launch

You have 3-phase motors with:
  • 1-ph AC brakes (with has an internal rectifier)
  • 24V DC brakes
  • 3-ph AC brakes
The 3-phase brakes are larger and more powerful.

This mechanical brake is not to be confused with DC injection braking or any other type of electrical brake.
But it is common to do both. Brake the motor with the inverter drive using DC and then when it has stopped and it's in standstill the mechanical brake is activated. There is a little overlap between this two types of brakes.

Last edited by Pete.S.; January 1st, 2018 at 06:32 PM.
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Old January 1st, 2018, 07:20 PM   #9
kalabdel
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Thanks gentlemen. I will try to get more information but will take time. It has been informative .

Pete, the Emerson drive is Unidrive M200 8.5Amps
The attached extract from the Lenze manual shows a voltage of 180VDC for a 400VAC line voltage which I believe is rated voltage for that machine. No mention of suppression though but I will contact their customer support, which is superb, for clarification


Thanks
Kal
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Old January 2nd, 2018, 07:31 AM   #10
Gene Bond
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One of the concerns for larger brakes is the operation time delay when the power is removed, due to the field collapse and resulting magnetic field. In some cases, the snubbers are used to collapse the filed quicker so the brake reacts much faster.

We recently had a customer who was experiencing a 1/4-1/2 second (or more) delay in brake activation when shutting off the full-voltage contactor/starter. This was a safety concern. By adding an MOV to the brake circuit (via a n/c contact on the starter), the field (thus the resulting voltage/current) had a path to collapse into, and reacted much quicker. This was documented (though not clearly) in the Sumitomo manuals.

Here is a little better explanation by Warner Electric: http://www.machinedesign.com/news/su...hes-and-brakes
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Old January 2nd, 2018, 12:22 PM   #11
kalabdel
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Thanks Gene, that makes a lot of sense. The machine with the MURR successor is a milk crate stacker/destacher and precise movement is important.

Kal
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Old January 2nd, 2018, 03:03 PM   #12
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I would consider this answered by Gene and Pete and I'm going to vere slightly off topic, but I want touch on drives and brakes:

The majority of servo drives and many VFDs I've worked with have dedicated brake outputs that are intended to directly drive 24VDC brakes built into the motors. I constantly run into people that have overly complicated this. It is super unusual to legitimately need to do something besides wiring the 1 motor's brake directly to the brake output of the controlling drive and your multi-axis gantry or robot or whatever is not an exception.

Of course lifting applications with external brakes can get special, but I see servo gantry "robots" with the brakes wired together all crazy for no reason all the time.
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Old January 2nd, 2018, 03:33 PM   #13
lpc921
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Quote:
Originally Posted by Gene Bond View Post
One of the concerns for larger brakes is the operation time delay when the power is removed, due to the field collapse and resulting magnetic field. In some cases, the snubbers are used to collapse the filed quicker so the brake reacts much faster.
I am going to disagree with this point here. No subber provides the fastest way to turn off a coil. Varistor is much faster than plain diodes. The varistor is included for over-voltage protection to increase contact life, without introducing significant switching off delay.
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Old January 2nd, 2018, 04:51 PM   #14
Gene Bond
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Quote:
Originally Posted by lpc921 View Post
I am going to disagree with this point here. No subber provides the fastest way to turn off a coil. Varistor is much faster than plain diodes. The varistor is included for over-voltage protection to increase contact life, without introducing significant switching off delay.
Realize a lot of these brakes are actually DC coils fed through a rectifier.

Here's the actual document we were referred to by Sumitomo:

https://www.sumitomodrive.com/upload...s/file-157.pdf

It shows the MOV used in the 'Quick Braking Circuit', and I can attest to the delay which it reduced / eliminate...
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Old January 2nd, 2018, 05:05 PM   #15
lpc921
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Rectifiers have internal over-voltage protection usually in the form of a flyback diode, with or without a series zener diode for faster application of the brake. The addition of MOV can further speed up the brake engagement by dissipating the energy faster. The rectifiers doesn't include MOV internally because the size of the MOV depends on the application.

However, in OP's diagram there is no brake rectifier in the drawing, unless it's integrated in the brake itself. If no MOV is used, energy from the collapsing magnetic field dissipates by arcing across the contractor, which will be even faster than using a MOV.
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