OT: Sew Eurodrive servo gearmotor BR brake

I have been searching the SEW website for a while now looking for an explanation of the operation of the BR style brakes used with their line of servo gear motors.

We have a machine that is less than two years old and has suffered four motor failures, two of which definitely seemed to be brake related. Now I am questioning the brake control circuit, which is a little different than my past experiences, and not too well understood by our contact at the OEM.

The OEM is also working on this problem for us, I just wanted to study the mfg docs and double check the circuit design and be able to test it. I have found literature for several other brake designs made by Sew Eurodrive, but not the BR series.

EDIT: The whole motor part number is FH47B/CM71M/BR/TF/RH1M/SB80

Any help appreciated.
Paul

It's been too many years since I worked with SEW motors but most of our problems were due to excessive gap. Keep it on spec, toss the brass spacer if there is one, and toss out the coil if it's resistance changes.
I don't know who makes a better brakemotor but I sure don't miss SEW motors .
Steve.

Hi Paul,

We have a ton of them... I have had very good luck

Just a WAG is your break resistor to small or faulty, do you have an external break contact have you tried changing it.

The gap on ours that have breaks is set to about 10 thou, if I can see daylight then its good, if there is a lot of dust then the break is working hard (but it may need to)

Is your controller a Movidine? I have a lot of older Movitrac's but they are good, I have an older MCD Tools program that's nice if you need it, but its for the older drives
Dick or someone may know this answer as I don't think its a SEW issue, I think its just a drive issue

The drive is a Movidrive Compact. The motor is a synchronous permanent magnet gearmotor with integral resolver and brake. It is in a washdown environment operating an indexing conveyor that cycles about once every 5 or 6 seconds, running for about 1.5-2 seconds each time.

As long as the e-stop circuit is energized, the motor brake coil is powered and released. The drive holds the motor at zero speed during normal operation between index cycles.

Below the drive in the main control cabinet, there is a control module for the brake with 5 terminal points. There are 3 wires going out to the brake, apparently it has two coils to optimize response time.

The first failure occured within the machine warranty period so they replaced it about 4 months after start up of the equipment. The 2nd one failed about two months later. I was not involved in those issues, so I can't say for sure what the symptoms were.

In May of this year they got me involved due to "Lag Error" faults. It seemed that when the motor was cooled down, it would operate just fine, and gradually begin to draw more current as the motor heated up. All of the heat appeared to be coming from the area of the integral brake. After an hour of running, it would beging to fault more and more frequently.

After verifying we did not have a mechanical issue, we replaced the motor and the problem was resolved. The new motor came with a new brake module in a bag zip tied to it, so I went ahead and installed it since the brake was my main suspect. I don't understand the wiring and operation of this module, I just replaced it wire for wire as the old one was installed.

Then again a couple of days ago, the replacement motor failed with similar physical symptoms, but a different fault code. Again, a new motor fixed the problem.

I studied the electrical drawing of the brake circuit, took some voltage readings, and called the OEM of the machine. One of the first things the tech support guy said was "I don't understand how that brake module works, but maybe it has failed?" Then I told him that we had replaced it once already, and we seemed to be getting 24volts to two of the leads going to the brake coil.

He offered to get more information for me on the module and compare my readings with a similar machine at their facility, but he hasn't called back yet. I will give him a ring about 9am and see if I can learn more.

Thanks for the input so far!
Paul

Two breaks, one for very fast and the other is for fast... I don't get it but we have them also, if I need the break to be on (locked) I want it as fast as I can all the time, why not... why would I ever want a slow break?? or if I want it to be off...

The majority of ours also have holding breaks (like yours)we use the drive to stop, one thing that I did on one of ours (and it did not cause a safety issue) was remove the break from the motor, opened the end and removed the pads and springs, that was 3 years ago and we have never had an issue with that one yet

It sounds like something is failing in the break circuit and yours is coming in to late? or not coming in at all, can you increase the delay to insure that the break gets energized or do you have a set of auxiliary contacts that you can use to stop it if its not closed?

Just a thought...

geniusintraining said:

It sounds like something is failing in the break circuit and yours is coming in to late? or not coming in at all, can you increase the delay to insure that the break gets energized or do you have a set of auxiliary contacts that you can use to stop it if its not closed?

Just a thought...

Click to expand...

The brake is held on (released) all day (and all night) long unless they hit an e-stop, or it is locked out for repairs. Once production ends for the day (usually 3-4pm) the machine sits there with the brake still energized (released) and the drive still enabled, holding zero speed while it is cleaned, and sitting idle overnight. I believe the machine is run in a "clean mode" with power still applied during sanitation.

So, the delay is plenty. The estop is reset, the brake releases and the drive is enabled with a zero speed command. Then usually after making mechanical set up adjustments, selecting a recipe and etc, they put the thing in auto, only after all that and several seconds later it will make its first index motion.

I got a call back from the OEM today, and the guy who is investigating our problem is off sick today. They are supposed to get back with me Monday. At this point I am not ready to modify anything, I just would like to know how to test this BSG brake controller and the brake coil itself to ensure we are wired correctly. So far, it appears that our wiring does match the sketch on the BSG module.

I appreciate your input, Mark.

Thanks
Paul

Here is some documentation on the SEW brakes, including the BSG: http://br.sew-eurodrive.com/download/pdf/11354615.pdf. Check chapter 10.8. The brake has two coils: one strong coil to release the brake and one that has been put in serie with the first one after a while to hold the brake. It's like a flippercoil from a pinballmachine.

I've had a problem with a servo control and a movidrive once too. The drive gave strange errors a coupler of times a day and the motor was pretty hot too. In the end it turned out somebody had commisioned the inverter with the wrong motor type (As far as I remember, you can find back the parameter the system has been commisioned with via Movitools).
After recommisioning the inverter with the correct motortype: still no luck. Only after giving the inverter a factory reset and then a new commisioning with the correct motor type it worked fine. Apparently some parameters got stuck in there.
Our SEW supplier told me that a commisioning with the wrong motor type could destroy the motor after a while. Maybe it's something worth checking.
Just make sure you have a backup of your inverter and your OEM's settings for the terminals and maybe fieldbus before you consider a factory reset.