Output voltage from mains driver?
Hi!
I’m looking at 2 different drivers for a 8,2Nm Nema 34 stepper.
Options are the Leadshine Am882 or DM2282.
I calculated the maximum stepper voltage to 66V. (8 wire, 4,2mH, 6,4 A in Bipolar parallel.)
The PSU that I would build for it would give about 75V, I guess it won’t hurt but... (Writing this made me see that the DM2282 seem to be the better choice all things considered.) :smug:
One question remain. I haven’t really got what the output voltage to the stepper would be using the Leadshine DM2282 mains driver??
Re: Output voltage from mains driver?
Quote:
Originally Posted by
JW1977
Hi!
I’m looking at 2 different drivers for a 8,2Nm Nema 34 stepper.
Options are the Leadshine Am882 or DM2282.
I calculated the maximum stepper voltage to 66V. (8 wire, 4,2mH, 6,4 A in Bipolar parallel.)
The PSU that I would build for it would give about 75V, I guess it won’t hurt but... (Writing this made me see that the DM2282 seem to be the better choice all things considered.) :smug:
One question remain. I haven’t really got what the output voltage to the stepper would be using the Leadshine DM2282 mains driver??
Hej!
I don't know the DM2282 and can't give you more than what I have just recently measured on my system, which uses the DQ542MA drivers, which are fake Leadshine analogue 4.2A drivers for my 3A NEMA 23 steppers.
In fact, I made three short YT movies also.
https://youtu.be/m1zxi-BjIhc
The first one is what is measured on the input. My DIY PSU (toroidal transformer based) gives about 43VDC without load. This voltage drops a bit when the drivers are enabled and the motors are running. The current measured on the input to the drivers is not really true because I don't think that those cheap meters can cope with the fast changes, but it gives an indication of the behaviour.
The second video is about voltages on the Z motor coils.
https://youtu.be/WVLjoR4yyW0
Note that the voltage is AC, if measured with a DMM it is important to set it to AC otherwise the reading will be false and totally off and unrealistic. Note also that my DMMs are accurate enough between each, and the differences you see in the voltage between the two DMMs are real differences. I think it is caused by the driver not being properly calibrated and balanced on both outputs. I don't know is all my drivers would demonstrate similar errors, but on this one there is definitely a difference between the coil voltages. If the differences matter or not... well, I have no idea. Perhaps I will redo this measurement just to see if there is a difference between drivers, because due to a f...up during the next video I killed the driver and had to swap it with a new one.
The third video is about measuring the voltage and the current AND the AC frequency of one coil of the Z axis.
https://youtu.be/iC5mDShOSts
It was here I realized that an ordinary DMM can not be used for the measurements. Especially the current measurements are wrong. My DMM has a frequency response of 400 Hz and that's not enough because the frequency is well above that, so the current is totally wrong, especially when the stepper is moving. After measuring the current and making the first part of this vid, I wanted to measure the frequency, so I hooked up the left DMM for frequency measurement. The only thing is that I forgot the twist the switch to Hz, and forgot to move the probe from the 10A input of the DMM to the Hz input, which meant the motor coil was shorted by the shunt and that instantly killed my driver. I have several, so no big deal, but pretty annoying. Will have to fix the fried one later, but for now I just swapped it out.
So, back to your question, the voltage over the stepper coils should be the same as the DC voltage input to the drivers. That is what I measure. The only difference is that the drivers are driven by DC and the output to the steppers is measured AC. I think if you measured yours you would come to the same conclusions. The frequency may be different for your drivers, but the behaviour should be the same or very similar as my three videos show.
BTW, if you decide to measure be careful. Use my post for learning and not making the same stupid mistake I did, because that might fry your driver, just like I fried mine.
Regarding the DM2282, the manual says "theoretical output voltage of 80~220VAC" and that it has a "motor auto-identification and parameter auto configuration feature" which should take care of the output voltage for you.
The Am882 needs DC power supply and the way I interpret the manual that you have to be more careful with that one. I think the output voltage will be the same as the input voltage, according to my measurements on my driver.
I am not sure which one I'd chose, but probably the DM2282 because that does not require a rectified input voltage and can use the AC directly from the transformer.
Re: Output voltage from mains driver?
Hej! :smile:
Thank you, interesting to see!
The Leadshine DM2282 is a "mains" driver, ( 220V.)
If I would have used the AM882, the stepper would have got about 75V.
That’s a little more than the calculated max (66 V) but i guess it would have worked.
With the DM2282 I get more margins and I won’t have to build another PSU so the cost will be about the same.
I know it works because I can see it being recommended here and there but I can’t get what the output Volts will be?
1 Attachment(s)
Re: Output voltage from mains driver?
Quote:
Originally Posted by
JW1977
Hej! :smile:
Thank you, interesting to see!
Hej igen!
Thanks.
Quote:
Originally Posted by
JW1977
The Leadshine DM2282 is a "mains" driver, ( 220V.)
If I would have used the AM882, the stepper would have got about 75V.
That’s a little more than the calculated max (66 V) but i guess it would have worked.
With the DM2282 I get more margins and I won’t have to build another PSU so the cost will be about the same.
I know it works because I can see it being recommended here and there but I can’t get what the output Volts will be?
The way I interpret the manual of the DM2282 is that it can use DC or AC supply. The DC input range is 115~305VDC and the AC is 80~220VAC. It is NOT the mains you normally connect to the input directly, but through a transformer.
Attachment 21246
I see two major reasons for this, one is personal safety, the other is that the mains in Europe is NOT 220V, so I would not connect it directly to the mains. Basically, if you want to build a PSU, that's fine, but regardless of which, you don't need it if you use the DM2282, you just need a transformer, but if you build one you can still use the DM2282 because it can use both DC and AC supply.
Here is a link to the manual, in case you have not seen it yet:
http://www.leadshine.com/UploadFile/Down/DM2282d_P.pdf
My guess is that the output voltage will be (if using AC as supply): 1.41 x the AC supply voltage. If DC supply is used then the output will be the same as the input voltage if measured as I measured the voltage.
Re: Output voltage from mains driver?
A_Camera, for those kinds of tests, you really need to use an oscilloscope, and you might want to see what happens when you put some extra load on an axis (even just lean on the Z axis as it runs), and at varying speeds.
JW, either drive would work. If you never run the motors at high speed (or not for long periods of time), then a higher voltage should not be a problem. A higher voltage would give better acceleration/performance, but the big risk is overheating the motor. That could be counteracted by reducing the current, but then you would lose torque.
You do realise that even though the DM's are high voltage drives, you still need to provide an appropriate input voltage? So the only thing you would realistically save, is a bridge rectifier and capacitor(s), as you'd still need an appropriate transformer.
Re: Output voltage from mains driver?
Quote:
Originally Posted by
m_c
A_Camera, for those kinds of tests, you really need to use an oscilloscope, and you might want to see what happens when you put some extra load on an axis (even just lean on the Z axis as it runs), and at varying speeds.
Yes, I know, but I did not want to hook up my scope because I might fry it (or the driver) since it is not isolated from the mains so I might get a grounding issue. If I had a battery driven scope I would have hooked that up, but I don't.
Regarding extra load, I am not sure it matters, I believe it does matter, but just recently had a discussion about that on CNC Zone, and one person said it does not matter. Basically because steppers are not real motors, just some solenoids which are switched on and off to get the motion we want. I don't know, but I believe (have a sense) that he is wrong, current will increase (to the maximum limit set up on the driver) if the motor is under load. Maybe that will be my fourth measurement...
Quote:
Originally Posted by
m_c
JW, either drive would work. If you never run the motors at high speed (or not for long periods of time), then a higher voltage should not be a problem. A higher voltage would give better acceleration/performance, but the big risk is overheating the motor. That could be counteracted by reducing the current, but then you would lose torque.
You do realise that even though the DM's are high voltage drives, you still need to provide an appropriate input voltage? So the only thing you would realistically save, is a bridge rectifier and capacitor(s), as you'd still need an appropriate transformer.
Yes, it is VERY important to use a transformer since 230VAC x 1.41 = 325V and that is VERY high for steppers and extremely dangerous to use in our DIY machines. I am not sure that the steppers will survive that, not even for short periods.
Re: Output voltage from mains driver?
Solenoids take more current if you load the plunger, as you disrupt the magnetic field. The essential law of physics, that you don't get anything for nothing, applies.
If I had the time, I'd built a dynamometer to run some tests. I have the plans for one, just not the time.
Re: Output voltage from mains driver?
Quote:
Originally Posted by
m_c
Solenoids take more current if you load the plunger, as you disrupt the magnetic field. The essential law of physics, that you don't get anything for nothing, applies.
Yes, that was my argument also, but since I have not measured it, for me that's just based on logical thinking and what I also learned a long time ago. Never the less, I won't argue further with him about it, so I dropped that question. Also since measuring the current is not that easy with my instruments, it is not easy to present a proof so for now, moving in air will do but yes, I expect some significant current increase if I'd measure under load.
Quote:
Originally Posted by
m_c
If I had the time, I'd built a dynamometer to run some tests. I have the plans for one, just not the time.
Well, time is ALWAYS a constraint. If we do something boring then the time never ends and a minute might feel like an hour, if we have fun the time is over before we know it and an hour might feel like a minute... :)
Re: Output voltage from mains driver?
Quote:
Originally Posted by
m_c
JW, either drive would work. If you never run the motors at high speed (or not for long periods of time), then a higher voltage should not be a problem. A higher voltage would give better acceleration/performance, but the big risk is overheating the motor. That could be counteracted by reducing the current, but then you would lose torque.
You do realise that even though the DM's are high voltage drives, you still need to provide an appropriate input voltage? So the only thing you would realistically save, is a bridge rectifier and capacitor(s), as you'd still need an appropriate transformer.
Yes, i realise that, now. I thought the DM2282 had a built in PSU ready for mains DC.
As i mentioned above, optimum would be about 66V for the stepper and the PSU would give about about 68V IRL if use a 50V transformer.
AM882 can be supplied with up to 80V and handle 8,2A so the figures add upp pretty nicely.
Leaning towards 3x AM882. (Can they be bought fair closer than China i wonder?)
