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  1. #1
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    Nema 23 motor comparison

    Hey all,

    First post! Whoot! Long time lurker though.

    I have been researching my build for a few months now and am getting hung up on nema motor inductance. How do these two compare:

    Motor 1:
    Holding Torque 1.9Nm(269oz.in)
    Rated Current/phase 2.8A
    Phase Resistance 1.13ohms
    Voltage 3.2V
    Inductance 5.4mH±20%(1KHz)
    Weight 1.1kg

    Motor 2:
    Holding Torque 1.9N·m (269oz·in)
    Rated Current/phase 3.0 A
    Phase Resistance 1.2 ohms
    Rated Voltage (≠driving voltage) 3.6 V
    Inductance 3.7 mH ±20%
    Weight 1.1 kg

    So I know the second is better as it can be driven faster and with more torque with comparable voltage. I just need an equation or some way to know HOW MUCH BETTER and where/when.

    Inductance section of this was helpful but I was getting weird results and no way to compare the results.
    https://www.duet3d.com/wiki/Choosing...ors#Inductance

    Constants:
    36v power supply
    Tb6600 or similar driver
    1605 ballscrews
    27" x 33" cutting area
    Home built grbl controller
    Dual y axis (4 motors total)
    Use: Mostly wood working with a bit of plastic and al.
    Me: technical and a woodworker, NO electrical or engineering background so 5yo version please.

    Thanks all!
    Happy to be here!

  2. #2
    Community Moderator ger21's Avatar
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    Re: Nema 23 motor comparison

    Lower inductance will give you more torque at higher speeds. You're looking at about a 30% difference in inductance, so I'd definitely go with the lower inductance motor, as it should give maybe 20-25% better high speed performance. And you'l;l need it, because 1605 ballscrews need to be spun fast to get any speed out of the machine

    Both of those motors should really be driven at 60V or higher, for best performance. At 36V, you're already limited to about 1/2 the speed that those motors are capable.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  3. #3
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    Quote Originally Posted by ger21 View Post
    Lower inductance will give you more torque at higher speeds. You're looking at about a 30% difference in inductance, so I'd definitely go with the lower inductance motor, as it should give maybe 20-25% better high speed performance. And you'l;l need it, because 1605 ballscrews need to be spun fast to get any speed out of the machine

    Both of those motors should really be driven at 60V or higher, for best performance. At 36V, you're already limited to about 1/2 the speed that those motors are capable.

    An thanks, yeah, I was concerned about the 36v. Ok, I might up that a bit. How did you get to the 20-25%?

    Thanks for the quick reply.

  4. #4
    Community Moderator ger21's Avatar
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    Re: Nema 23 motor comparison

    Just a guess, based on the difference in the inductance. The only way to know the real difference would be to find manufacturers torque curves, using the same voltage, same drives, and same settings. Not likely to happen.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  5. #5
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    Quote Originally Posted by ger21 View Post
    Just a guess, based on the difference in the inductance. The only way to know the real difference would be to find manufacturers torque curves, using the same voltage, same drives, and same settings. Not likely to happen.
    Ah got it. So last question. Assumjng you can get enough voltage to the higher inductance motor, is there any reason it is better? In other words, should I stick with motor 1 and just get bigger drivers and power supply?

  6. #6
    Community Moderator ger21's Avatar
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    Re: Nema 23 motor comparison

    No, I'd always get the motor with lower inductance, given the choice. Unless you already have the motors.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  7. #7
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    Re: Nema 23 motor comparison

    Like Ger said, If you don't have them yet, go for the lower inductance. unless the price difference is not acceptable.
    Here some calculations.
    how to rughly calculate a max stepper speed.
    Inputs needed for this: Motor peak current ( Amp ), Motor Inductance ( mH ) , Motor steps per rev, Driver High voltage
    Rpm = 60 * Voltage * 1000 / Inductance * 2 * motor peak current * steps per rev
    In your case, for the first motor
    60 * 36 * 1000 / 5.4 * 5.6 * 200 = 357 rev per minute
    the second motor comes at 486 Rpm on 36 V and if at 60 volts 810 Rpm
    Good luck.

  8. #8
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    Re: Nema 23 motor comparison

    Yeah, that's a fairly major difference. I already had the first motor and returned them, but the second motor was actually cheaper so it was a wash with return shipping.

    Also, the drivers I'm going to use are rated to 42v {tb6600 - I know, I know...). But stepping up (pun intended) to a 80v driver, individual PSUs etc really blowes the budget. Then I might as well go 3nm or a nema 34..... You see where this is going.

    It's my first machine and really only for wood, so I'm sure it will be rebuilt and upgraded many times. I'll start a thread as the pieces come together.

    Thanks all, really helpful.

  9. #9
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    Re: Nema 23 motor comparison

    The trouble is these cheapo Chinese motors use thin wire and lots of turns: high static resistance and high impedance.

    You may try to find some 2nd hand US made motors , generally bigger foot print and nominal ratings like 1.65V. Just make sure that your drivers can cope with that.

    If your NEMA23s are 6 wire jobs, look at wiring them in half coil mode, using the centre tap wire. Remember that the current rating is the static short-circuit current they will take without going into magnetic saturation and over-heating. Most of the time you will not get that much into the motor.

  10. #10
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    Re: Nema 23 motor comparison

    Nema 23 stepper motor are more powerful then Nema 17 stepper motor.
    NEMA 17 is a hybrid stepping motor with a 1.8° step angle (200 steps/revolution). Each phase draws 1.2 A at 4 V, allowing for a holding torque of 3.2 kg-cm. NEMA 17 Stepper motor is generally used in Printers, CNC machines and Laser Cutters.
    https://www.rawlix.com/product/nema-...52358233288547
    https://www.rawlix.com/product/bipol...52260968682280

  11. #11
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    Re: Nema 23 motor comparison

    Quote Originally Posted by fahad12 View Post
    Nema 23 stepper motor are more powerful then Nema 17 stepper motor.
    NEMA 17 is a hybrid stepping motor with a 1.8° step angle (200 steps/revolution). Each phase draws 1.2 A at 4 V, allowing for a holding torque of 3.2 kg-cm. NEMA 17 Stepper motor is generally used in Printers, CNC machines and Laser Cutters.
    https://www.rawlix.com/product/nema-...52358233288547
    https://www.rawlix.com/product/bipol...52260968682280
    First of all NEMA17 and NEMA23 are standards for the physical mounting dimensions they are NOT a stepper motor. Your statement about specific motor type and geometry are NOT part of the standard and are totally irrelevant. NEMA17 is NOT "a hybrid stepping motor ", it is not a motor at all.

    Second, NEMA17 sized stepper motors are going to be too small for most CNC applications and only suited to light work like prints ,3D prints and lazer cutters where there is no cutting force, just displacement.

  12. #12
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    Re: Nema 23 motor comparison

    Quote Originally Posted by ShallowPass View Post
    Hey all,

    First post! Whoot! Long time lurker though.

    I have been researching my build for a few months now and am getting hung up on nema motor inductance. How do these two compare:

    Motor 1:
    Holding Torque 1.9Nm(269oz.in)
    Rated Current/phase 2.8A
    Phase Resistance 1.13ohms
    Voltage 3.2V
    Inductance 5.4mH±20%(1KHz)
    Weight 1.1kg

    Motor 2:
    Holding Torque 1.9N·m (269oz·in)
    Rated Current/phase 3.0 A
    Phase Resistance 1.2 ohms
    Rated Voltage (?driving voltage) 3.6 V
    Inductance 3.7 mH ±20%
    Weight 1.1 kg

    So I know the second is better as it can be driven faster and with more torque with comparable voltage. I just need an equation or some way to know HOW MUCH BETTER and where/when.

    Inductance section of this was helpful but I was getting weird results and no way to compare the results.
    https://www.duet3d.com/wiki/Choosing...ors#Inductance

    Constants:
    36v power supply
    Tb6600 or similar driver
    1605 ballscrews
    27" x 33" cutting area
    Home built grbl controller
    Dual y axis (4 motors total)
    Use: Mostly wood working with a bit of plastic and al.
    Me: technical and a woodworker, NO electrical or engineering background so 5yo version please.

    Thanks all!
    Happy to be here!

    They're both pretty frikkin high inductance to me for that size torque. Stepper online's garbage by any chance?
    Personally from my limited experience, when it comes to driving 1605 ballscrews I'd be looking at something like these:

    https://www.automationtechnologiesin...flat-570-oz-in
    These have 2.5mh inductance and I've seen them widely used around the forum on many different types of machine. Ran from 60V PSU's and drivers, and they fly.
    http://www.automationtechnologiesinc...ownload/17251/
    http://www.automationtechnologiesinc...ownload/14762/

    I wouldn't touch less than 425oz/in for 1605. I've also ran on 36V when I started out and had nothing but grief with stalling, crap accel, low top rpm etc etc.
    Don't waste your time and money. Get it reliable first time!!!!

    As I live in the u.k. I was a bit limited with what I could get due to ridiculous import charges and the like. On my mill machine I've ended up with 566oz, 5A, 3mh Nema 24 size steppers running on 60V. I had to shop/search around a fair bit to find what I wanted as close as possible to the above. I am happy and wouldn't have anything less again!


    If mine ever cop out. I reckon these will be my next:
    https://www.aliexpress.com/item/1005...160c3421Llz8x3
    https://www.aliexpress.com/item/1005...archweb201603_
    Run from a 60VAC toroidal.

  13. #13
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    Re: Nema 23 motor comparison

    Yes lots of good kit in US is pretty inaccessible, even most firms won't ship outside US/Canada. Maybe this will change with whatever trade deals are put together but I think it's mainly about jurisdiction and not being able to chase up dishonest customers abroad.

    Thanks for the link, odd that their doc does not seem to state the inductance !

    Inductance is what kills top speed, if you look at the "square" pulses you are feeding the motor they quickly get deformed beyond recognition and the current delivered to the motor windings drops so low you have very little torque.

    I found some chinese NEMA24 from Wantai, which had pretty good inductance and work quite well. You need to pick the right model if you want low impedance.

  14. #14
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    2152

    Re: Nema 23 motor comparison

    I wouldn't be overly concerned about the stepper choices to select from, so long as you aim for as low an inductance as possible, and around 270-300oz/in at a minimum, anything in that range or a bit above will be more than adequate for machining wood. The spindle probably is a slightly more critical factor in how efficiently you'll be able to machine wood.

    Going too large a stepper than needed can actually have an adverse effect.
    It's rumoured that everytime someone buys a TB6560 based board, an engineer cries!

  15. #15
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    Re: Nema 23 motor comparison

    Quote Originally Posted by reg.miller View Post
    Yes lots of good kit in US is pretty inaccessible, even most firms won't ship outside US/Canada. Maybe this will change with whatever trade deals are put together but I think it's mainly about jurisdiction and not being able to chase up dishonest customers abroad.

    Thanks for the link, odd that their doc does not seem to state the inductance !

    Inductance is what kills top speed, if you look at the "square" pulses you are feeding the motor they quickly get deformed beyond recognition and the current delivered to the motor windings drops so low you have very little torque.

    I found some chinese NEMA24 from Wantai, which had pretty good inductance and work quite well. You need to pick the right model if you want low impedance.
    I have Wantai WT57STH115 on a Sieg. 425oz, 4.2A, 3.8mh.
    Crappy on 36V, great on 60V. Wantai aren't a bad motor tbf.
    I wanted the 57BYGH115-007 with the ind of 2.3mh initially but could not get them at all.

    My 566oz 60BYG401-03 (8 lead parallel wired) ones are on my 25LV.

    If I lived in the U.S. I'd only go to Automation Tech.

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