Kollmorgen AMK54G vs 54K

Calling anyone with experience of the Kollmorgen motors. I’m on the brink of pulling the trigger on an AKM build, and am leaning towards the 54K as my motor of choice.

I’m a little unsure of the differences between the G and K windings in terms of characteristics - I understand the K will peak at around 26Nm and the G 24, but should I consider any other factors?

For example the K windings take a lot more power - does this imply less smoothness in the feel?
Would love to hear any opinions from people who have experienced both windings.

Hello there, unfortunately i cannot answer your question but rather take it a little further in the hope it will rekindle this thread and someone with knowledge responds! Hopefully this is not considered hijacking! I am very new to the OSW world and trying to understand Kollmorgen motor windings myself.

Is there any reason other windings cannot be used? I have a (very cheap) AKM52M which I am looking to use for this purpose. So far, my very basic understanding is that it will require a power supply with somewhere in the order of 1600W to get the full peak 21.9Nm it is rated for. Happy to go with a smaller PSU and reduce the Torque if that is indeed how it works. The motor is rated at 4500rpm which is much higher than the K so not sure what impact that has.

Can anyone explain windings please?

Having played with both G and K windings, I have to say I prefer the K winding AKM servos, as they certainly feel a bit smoother under IONI operation than the G.

Just ensure you are able to realize the torque you are after, I suspect you will be ok though, as I think I got approximately 21 or 22NM from my 53K.

The K windings do run a bit hotter under full-torque operation vs the G in my experience, but this in no way diminishes the performance, these are designed for 24/7 high temperature operation any way.


There is no reason any given winding cannot be used other than it’s power requirements to meet a given performance target. In theory the ‘hotter’ windings which are rated for higher RPM’s should have faster response and generally be a quicker or more aggressive motor. 1600W is a huge amount of power to draw for a 20Nm target, a small Mige or 52G will hit that with a 480W power supply by and large.

My impressions of the 54K are super-positive, it feels super smooth, super fast and responsive and can deliver brutal jolts on large bumps and off tracks, its great. I don’t have any reference point to compare against however as this was my first OSW build. In terms of heat - I generally run at around 35%, and there is no perceptible heat up what-so-ever. As Beano rightly says, these things are designed to run in much unfriendlier environment than our sim-rigs, so heat is really a non-issue.

All of those motors can hit 20Nm probably with 100W. Static torque power draw is not high. Power is Voltage x Current. Current is toque. Voltage is speed.

If winding is done for high speed - motor is going to be either lower torque or larger or more expensive. And response decreases with motor mass, winding capacitance and lower torque limit. So, no, you want to have motor rated just above your target.

No. You calculate the 3 phase motor copper losses by (I_RMS)^2R1,5 where R is phase to phase resistance. If you want to calculate the shaft output power from the motor, that is 2pif*torque (in Nm), f in the previous formula is rounds per second.

Sorry, I didn’t meant it literally. All I said is - full torque does not require full power. And full power depends on speed. And I also gave arguments about higher speed motor advantage.

Hello and thank you for the responses. I have followed an old thread on isrtv by JonnyK where there are responses from the Granite Devices team (towards the end of page 1 in purple - Link and calculations in the attached pdf). If i understand things correctly (very unlikely :slight_smile: ) then the AKM52M servo can be used but with a reduced Peak Torque. I intend to buy a SimuCube and Ioni Pro HC for this build. However, I still don’t understand power requirements and would want someone to confirm that a) this servo can indeed be used and b) What power supply i need to get the best performance out of this servo. If i’m in the ball park with my calculations and the max torque i could get with ioni is 16.5Nm, I would be more than happy with that. It far exceeds my G27!

DLG OSW - Sheet1.pdf (2.5 MB)

That servo has a very low torque constant of only 0.66 according to the sheet you have posted. The IONI Pro HC can deliver ~17.67 Amps RMS, and thus at a torque constant of 0.66, the max torque you will see from that servo will be ~11.7NM.

This is quite low for the inout current, I would think you should get a servo better suited to this application. Unless you will be happy with that relatively low peak-torque, which may very well be the case.

For a PSU, I would porbably recommend the MW SDR-480-48, which would spike up to 750W or thereabouts…again, I haven’t input your numbers on my spreadsheet, can do so later tomorrow perhaps.

But yeah, that servo is not so good for this, it will eat power like crazy and still don’t provide much kick…why don’t you get a small mige or perhaps a 53K or 52G/53G or similar AKM servo?


ps: Note my estimates as just theoretical at best, like stated, I could probably enter the data to my calculations and get more firm numbers on the PSU wattage requirements…max torque though should be fairly close to the 11.7Nm


To be honest, I took a gamble and picked up this servo for $100 before i really knew anything other than i want an OSW wheel. I figured (rightly or wrongly) it was a quality servo with good resolution and the SFD model (which Bodnar uses in it’s V2 system). I am hoping to get anywhere between 12-16 Nm of peak Torque as from what i can tell, most people with 20-30Nm don’t run them at full torque anyway. With that said, 11.7Nm would suffice as long as there aren’t any other issues like poor responsiveness or fidelity. I’m sure it’s not the best suited servo, but it must be a big step up from a consumer wheel, no?

What is still unclear to me is the power requirements. If it requires something out or the ordinary then I wouldn’t proceed with this servo, but if it can operate using the same psu as say what a small mige would run, then i don’t see the harm in trying. I can always swap out the servo later so i don’t want to buy anything specific to only the AKM52M.

I’m trying to keep the costs down so a K or G are really not an option at this point, but a small mige might be if the M doesn’t cut it.

If you could crunch some numbers through your spreadsheet for me that would be amazing and will probably make the difference between proceeding and not. It would be very helpful to get other peoples views on this although i suspect most will say go with the small mige. This has been a great community so far and i hope to contribute throughout my project!

Many thanks,

In this use case full torque most often does means full power or very near the full power consumption, as the rotational speed towards the motor produced torque is very low. Majority of energy is turned into heat inside the motor, in the coils, as the energy is not in (large proportion) transferred to an external device via the shaft and consumed there. This (proportion) highly depends on how high torque linearity vs. rotational speed is desired.

You can get the full 11,7Nm static torque with this motor @ 230W / 0,93 = 255W. As the shaft output torque is about 11,7Nm as Phillip said, then, if you wish to get that torque with 2 rps top speed, then as output power you need ~150W as shaft output power, so, with 400W you get that 11,7Nm so that the output it is linear from 0 rps to 2 rps.

If that motor does not have suitable encoder that is supported by IONI Pro series, then the encoder needs to be replaced by a suitable one before you’re able to use the motor with SimuCUBE.

Hope this helps.

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This motor has an SFD encoder which i can find reference to on the IONI wiki. Does that mean it is not a compatible encoder? Here is the information I has found thus far:

“SFD is a resolver based feedback type. Resolver signals are converted to a serial protocol at the motor and then transmitted back to the drive. SFD also includes motor parameters in EEPROM memory to enable quicker/easier AKD drive setup with an AKM motor. Resolution is 2^24 count/rev.”

3rd POST from https://forums.ni.com/t5/Motion-Control-and-Motor-Drives/Seeking-clarification-on-SFD-in-AKM-Brushless-Servo-Drives/td-p/2835994

From Kollmorgen: https://www.kollmorgen.com/en-us/developer-network/sfd-feedback/

Attached is the model number key. The model is AKM52M-ANCNC-00

Dan, the SFD is electrically incompatible with the interface on the SimuCube, even if we could get licensing for the protocol.

Unfortunately it is not supported, and I doubt it will be - at least for the foreseeable future.

Hence my comment earlier, it will be significantly easier to sell that servo and get a small Mige, as refitting another supported encoder onto that one, will most likely run you 1/2 the price of a small Mige anyway.


Hi Beano, I guess that’s that then! Thanks for the info and responses. You are right and the best bet is to go with the Mige but If you can suggest any supported encoder please do. I would like to understand costs for a conversion just out of interest. You used a Kollmorgen EM with a Simucube right? Thanks again.