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S-327, the Russian trike I own

SBC Parker MB and Elau SB servo motor and drive compatability

This page will help me remember what I've found out and I hope it'll also get indexed by Google so that it might save someone else some time.

Summary

So far, it seems Elau SB servo motors can be used with SBC drives intended for SBC MB series servomotors, although you will probably need to correct resolver alignment using the Pr30 drive parameter. Not yet clear whether there's a 220/400 voltage issue.

Background

I picked up two LVD5 drives and an MB70 servomotor very cheap on ebay in a lucky purchase, with a view to using them in a DIY CNC milling machine project. These are AC brushless servo drives with quite a few control modes, including Canbus and step/direction stepper motor simulation modes (which is how I plan to drive them).

SBC LVD drives
The two SBC LVD5 servo drive units

SBC LVD drives
LVD nameplate

Both are made by SBC Elettronica, based in Milan, Italy, around year 2000 or maybe earlier. SBC were subsequently part of Parker Hannefin (SBC Division or Divisione SBC) or, later, just Parker. The SBC servos and drives are apparently especially well suited for use in the packaging industry, according to the brochures etc.

SBC website: http://www.sbcelettronica.it/ - for manuals, drawings, etc.

There is quite a bit online, including manuals, drawings etc for both drives and motors. There are copies at the Parker website too, and a bit of Googling for any of the model names will also find copies at various reseller/distributor websites.

Anyway, after checking that both LVD drives worked with the MB70 motor which came with them (they did) I wanted a second servomotor to go with the second drive. Buying a spare from a proper industrial servo supplier (in the SBC are imported by Amir Power and Quin Systems would be an option, but I didnt' want to waste their time with what I would be prepared to pay - very much hobby prices in two, not three figures. So about the only option was to find an ebay bargain...

There were a very few on eBay - searches for SBC bring them up. But all the sellers wanted silly money and besides, most were bigger motors too large for the drives I have (LVD5 i.e 5A continuous rasted, 10A peak). Or were versions with encoders instead of resolvers (check the model number codes - in the various motor manuals) which (I think) the LVD won't cope with.

However, I noticed this picture on one Ebay advert, on a motor which was described as an SBC SB70...:

SBC nameplate

That seemed to suggest that SB and MB motors were basically the same thing. In their other ranges the 'S' letter designates a salient pole version of the servomotor, with slightly higher performance but basically the same. So maybe that was the only difference?

So I also tried searching for 'SB' series motors, and that eventually turned up an 'Elau SB70' motor on German eBay, which looked visually identical to my MB70, and was a 0.99 euro start auction. Elau are a German makers of servo systems (also for packaging) and they have a system called PacDrive which looks a lot like some of the later SBC systems. Also, the full product name in the ebay auction followed the exact same format as the SBC ones. I guessed and hoped that the SB motors are simply rebadged MB ones. Later, I found this page from a repairer which said "Elau motors were originally manufactured by S.B.C., before S.B.C. was acquired by Elau.".

SBC LVD drives
MB nameplate.

SBC LVD drives
SB nameplate.

So I got a friend in Germany to buy it for me and send it over. Meanwhile downloaded the Elau documentation for the SB motors. Although the motors were very similar spec there are a few differences: the max speed (4000 vs 3800) and zero rpm torque (?? vs ??) so perhaps not just a straight rebadge...

SBC LVD drives
MB (left) and SB (right) motors are physically identical, apart from degree of wear and tear. Connectors used are identical, with identical wiring too.

It uses the same Mil connectors as the MB motor (checked via the docs, athough couldn't find a resolver pin-out for the SB. Also noted the SB motor has a temp sensor whereas the MB doesn't). Plugging it in and trying it with suitable settings on the LVD5 looked OK until the drive was enabled, at which point the SB 'ran away' at full speed.

Testing

After much checking and messing around with settings I tried the 'wiring test' diagnostic on the drive which came up with a 'resolver phase error' but no indication of how to solve that.

The resolver was clearly working - you can get the driver to display the absolute shaft position and it gives a perfectly good readout when you rotate the shaft by hand.

Back to Google and found this PDF, with the key phrase "MH and SMH Series motors have identical electrical and mechanical ratings to the MB and SMB series but are specifically for use with Parkerís COMPAX servo drives. The only functional differences are a change in resolver alignment and temperature sensor type."

So maybe the Elau 'SB' motor is a rebadged MH model, rather than a rebadged MB? As the drive has no input for temperature, the relevant wires just aren't connected, so that should make no odds. So that leaves the resolver.

So back to the LVD manual and notice that the 'Pr30' is for 'resolver alignment offset' "Used to correct electronically the mechanical position of the resolver". But no units given... eventually found (by searching for 'Pr30 resolver' in this manual for a later drive that it ranges from +32767 to -32767... which presumably covers 360 degrees...

Did consider removing the rear covers on the motors to see if there were alignment marks which might make it easier to set both the same but wanted to try software first...

So started testing with offsets incrementing by 1000 each time, enabling the drive after adjustment and seeing if it 'ran way'. Round 10000 it stopped doing this but the motor would 'creep' a bit at what should be zero rpm. A bit more offset and all seemed OK - it responded to the drive (testing using the -10 to +10V input with a 1.5V and then 9V battery). But it would error out with decimal points across the display after a few seconds (overcurrent error).

Eventually zeroed in on offsets which work... any of -19500, -8000 or +13500 seem about as good as it gets - I couldn't find a way to get it closer. You can adjust Pr30 while the motor's running, so get some idea from the sound. Also, I found that when the alignment was significantly out the speed at 9V input (around 3750 rpm as set up) would vary. Strangely it would go to full speed (3746) forwards without error, but in reverse would only get to around 3400 and would give the overcurrent error almost immediately.

By changing the Pr30 offset by 200 or so at a time and noting down the speeds attained in forward and reverse, I could guess at the centre of the 'good band' of Pr30 values, to get the figures as above. But I couldn't find a 'sweet spot' when both forward and reverse behaved the same. But they can be 'swapped' by going for the negative rather than positive Pr30 offset (e.g -8000 vs +13500 on mine).

Also, I found that the overcurrent error in reverse only happens at over 3500 rpm or so requested speed. Dial down what the drive is asking and it works with no errors.

Voltage?

Look at the motor castings and you can see stamped in ID:

SBC LVD drives
MB casting lettering: V220 G3800 NM1; Z02 0241.

SBC LVD drives
SB casting lettering; V380 G4000 NM1; Z98 10 70

Clearly that's voltage, max rated speed, nominal torque. I suspect Z is year of manufacture and the remaining digits are batch numbers.

Now if I'm running both on the LVD drives (via single phase UK 240V power), for which the 220V one was originally fitted, is the 380V motor being undervolted? 380V is typical UK three phase voltage. That might explain its reluctance to reach max speed (though not why the two rotation directions are not the same). It might also result in lower torque, but I havent' worked out how to test that easily just yet. And the LVD manual says you can run it either on single or three phase (derated slightly for single). The DC bus voltage might not be different between the two... might take another look at the Elau and SBC manuals to try to elucidate...

Or might just wait for the machine to be built and see how the two motors work...

Next?

Next is to build the machine then tune the servos under load. May use them as spindle drives as I already have stepper motors set up for XYZ.

Reference stuff not in the manual:

  • - LVD 24V plug: any 5.08mm pitch 3 way screw terminal block should fit. e.g. this at Farnell though I got mine off Ebay.
  • - LVD power and motor plug: Phoenix Contact PC 4 HV/ 6-ST-7,62 - PLUG, HV, SCREW, 7.62MM, 6WAY see e.g here at Farnell.
  • - Motor power plug: Mil ??? 7 pole
  • - Motor resolver plug: Mil ??? 10 pole


My workThe tandem trike which I builtS-327, the Russian trike I ownAckermann steering design spreadsheet - free downloadNotes about cheap and free CAD programsMisc stuff, including trailers and other bike stuff