Repairing a emerson M300 uni-Drive

Hello everyone 

today i got to spend more time with this drive.

first thing i did was identifing what has the same 0v referance point as suspect ic (ic14)

which included main DC negitive connector and op-amp ic LP2901  (ic27)

then measuse vcc from op-amp ic back to suspect ic  

result of suspect ic 0v on pin 5, 

vcc on pin 7 

so now using anilog meter on vcc to ov 

powering up unit  this voltage is pulsing from 8 to 18v

amazingly the power for this circuit can unplug  (PL1)

so with this unplugged I powered it up, and measure on socket to get stable 30v

removing this board after caps have discharged  ( 6 of 780uf in series with 6 of 780uf ) 

from the 560v there is resister devider which supplies this 30v

A-ha there is exploded suspect zenor diode 

and trying to clean around PL1 socket , i decided to remove socket 

A-ha  i found tracking under neath socket, so scraped this away 

put this back to geather and added 15v 5w zenor   

powered up. result 15v stable but no output 

fitted 20v zenor  result pulsing again  

so now wondering is op-amp and or suspect ic damaged 

there is a opto copler close by  

now running out of time for the day 

looking at data sheet for UC3842  looks possible, BUT time will tell.

acdc90 The 560 VDC is what you would expect to see (real world).  Your 400 VAC is RMS.  Once its been converted to DC, you get the peak value of what the RMS is.
RMS * 1.414 = PEAK       (square root of 2)

My experience with similar equipment is the DC-DC converter that gives you your 12VDC and 24VDC control voltage.  When you replace them, do so with larger capacity units.

I do agree that this is dangerous to the inexperienced.  Be sure to discharge the converter capacitors.  Older systems didn't have any safety discharge built into them.

Good luck.

Yes, this can happen. The switching-IC can have built in pump-booster with a voltage comparator.

So, we must know which controller, this 8-pinning device. 

May be one of this mounted: https://www.power.com/?segment=none#

Gerald

From my experience with other ac drives, the power supplies use electronic resettable fusing.  

The power supplies turn on, see a short circuit, turn off, pause a bit , retry -- i.e. pulsing. 

If all loads are removed and the power supply still pulses, there maybe a shorted component in the power supply , filter or suppressor,  or a short on/in the pcbs.  

Hi Michael,

yes, you're right, but I see, I'm also. Yes, I wish him all the best.

Look here, it's just one point:

Frequenzumrichter Emerson Unidrive M300-024 00041A 1,5kW | eBay.de

You can buy it used on eBay for around 190 euros.

I assumed he didn't have the schematic because he had indirectly asked for one.
His mention of 400V 3-phase power, a 560V DC intermediate voltage (after filtering), and the pulsating output voltage suggests to me that the IC and the MOSFET switch / -inverter bridge might be faulty.
Unfortunately, he can't read the component markings.

So, my advice would be to reverse-engineer the schematic from the unit itself.
BUT—
Step 1: !!Desolder the large electrolytic capacitors so they can't charge up and give him an electric shock!! But before desoldering unload it!

Step 2: Photograph the top and bottom of the circuit board and use a program like Windows Paint (or any graphics editor) to make the image semi-transparent; this makes the circuit traces and component outlines in the background visible.
That makes it easier to draw up the schematic.
Step 3: Locate all component markings and check their specifications in the datasheets; that makes finding a replacement part easier.
After all, finding the right component is often a problem if you can't get the original spare part.
-> That was the main problem with my repairs: being able to buy the original spare parts.
I often had to resort to using similar components instead.
The biggest problem arises when components have programmed software inside them, or when "standard" components actually
contain multiple parts within a single package—like transistors with built-in base resistors, etc.
etc... etc...

Anyway, before I posted my reply to him, I looked for the schematic but unfortunately only found the user manual.
I’ve repaired similar inverters a few times. Grrr... those specialized components always made life difficult for me.

I’m familiar with Emerson because I used to sell and install that kind of equipment. But unfortunately, a circuit diagram was never included.
Manufacturers like that only release their schematics to authorized companies for repairs and servicing—not to private individuals.

I really wish him the best, but I’m afraid he won’t be able to repair the device.

Best Regards

Gerald

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I'm hoping that  acdc90 knows what he's doing in general electric terms. He's been doing it a while and posting on E14 for 5 years and is still alive.

I sometimes fix stuff for a local agricultural engineer - they get customers with an old machine where the cost of a replacement electronic box is prohibitive or just not available.

So like adc90, I end up relying on common sense and experience trying to fix something with no manuals and no support from the original manufacturer. 

I think the success rate is about 50%.

But that is way better than the alternative.

I just fixed a big (really big) lathe for someone - manufacturer long since disappeared, it was made in Bangalore. Scary high power 3 phase control box  but they did put a schematic in the control box when they made it (about 1980). Since then people had changed things a bit without leaving any notes .

Scrapping stuff like this is crime (at least against the environment) and the repair probably saved them about £10k v the cost of a second hand replacement.

Sometimes it's the right thing to go for it (using nice long probes, a lot of care, and keeping one hand in your pocket.).

MK

Please! DON'T touch this device. This is an AC-AC multi frequency inverter which you can control and drive motors.
Just a specialist can repair this device.

https://www.manualslib.de/manual/241166/Emerson-Unidrive-M300.html?page=62#manual

I wish you all the best for your live.