512,393 active members
2,729 visitors online
Register for free
Login
Page 1 of 2 12
Results 1 to 12 of 17
  1. #1
    Registered
    Join Date
    Dec 2011
    Posts
    45

    Too much voltage?

    Hi guys I am currently running 1200oz in steppers I ignorantly bought as a kit a long time ago before even building my machine. Trying to gain some rpm so I'm looking at some 435oz in steppers. My current motors are rated at 5.6amps. surprisingly these particular smaller nema34 435oz in are rated at 6 amps. They are 8 wire motors though but will be used bipolar parrelel never the less. I have 60 volt power supplies. Is that too much for the smaller motors? I can reduce the current on the drives if needed but I don't want to have to replace my power supplies if I don't have to

  2. #2

    Re: Too much voltage?

    The stepper system input voltage is limited by the drives not the motors. In other words, feed them with the voltage your drives will take. I'm running mine at 75 and 80 volts depending on the machine. Running NEMA 23s and 34s, all 4 wire.
    Jim Dawson
    Sandy, Oregon, USA

  3. #3
    Community Moderator ger21's Avatar
    Join Date
    Mar 2003
    Posts
    34659

    Re: Too much voltage?

    I'm running Nena 23 motors @ 60V, with no issues.
    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)

  4. #4
    Registered
    Join Date
    May 2005
    Posts
    1397

    Re: Too much voltage?

    As Jim said, its up to the driver, not the motor.
    James hosts the single best wiki page about steppers for CNC hobbyists on the net:
    http://www.piclist.com/techref/io/steppers.htm Disagree? Tell him what's missing! ,o)

  5. #5
    Registered
    Join Date
    Jun 2012
    Posts
    115

    Re: Too much voltage?

    It's not because your drive can provide some power rating that it is the best choice for the motor.

    You need to ensure that you are not driving the motor winding into magnetic saturation for a sustained period at low revs or on on hold. Look at the current rating of the motor and the static coil resistance. Over stepping the current rating will just heat up the iron core in the motor without producing an ounce more effort. They will stand it for a short time but it is doing nothing but heating the motor.

    The coil windings should be able to stand the rated current indefinitely and hopefully the motor will have been designed to produce max. magnetic field ( ie magnetic saturation ) at that current.

    don't stick 80V across a 1 ohm coil rated at 3A , just because you can !

  6. #6
    Registered
    Join Date
    May 2005
    Posts
    1397

    Re: Too much voltage?

    Yeah... no. Hang on... That's mixing things up reg.

    Yes, you set the driver to the current rating of the motor (so looking at the motor current rating is right) but the OP was asking about voltage, and looking for speed. No one said anything about "overstepping" the current rating of the motor.

    The drive will regulate the voltage going to the motor in order to provide the correct current flow in the motor coil. Putting 80 volts into a 1 ohm 3 amp coil is exactly what you want to do for a faster step to the next position, but only for a fraction of a second. And the driver will do exactly that, if it has an 80 volt power supply feeding it (and is rated for that supply, of course) but then it will stop down the voltage quickly as the coil current reaches it's rated maximum (which it will do faster with the higher initial voltage) and will NOT saturate the motor. So increasing the voltage gets you more speed, as does moving to lower inductance motors, because those things get the coil to the rated voltage faster.

    Voltage = speed. Current = torque.

    Too slow? Reduce microstepping, Raise voltage (not more than the /driver/ rating), Move to lower inductance motors.
    Missing steps at low speed? Raise current setting on driver (not more than the /motor/ rating)
    Stalling at midrage speeds? Lower current, More microstepping / better driver, Add a vibration damper.

    To that standard list, I would add:
    Missing steps after the machine has been on for a while? Add heatsinks to the motors. (someone will give me crap about this, but I've seen it work too many times), Automatic drive disable after job end.
    Missing steps only when raising the Z axis? Add a spring / gas strut or pulley and weight for "anti-gravity", Increase current, Move to higher inductance motors.

    Correct me if I'm wrong, but that list would probably answer 3/4 of the questions on here, wouldn't it? Other than the "I'm new, what should I buy for this machine that I haven't told you anything about" questions.
    James hosts the single best wiki page about steppers for CNC hobbyists on the net:
    http://www.piclist.com/techref/io/steppers.htm Disagree? Tell him what's missing! ,o)

  7. #7
    Registered
    Join Date
    Jun 2012
    Posts
    115

    Re: Too much voltage?

    Yes James. I don't disagree with any of that. But beyond a point extra voltage gives diminishing returns and just produces more heating in the driver. The first thing is to ensure that you are not pushing worthless current into the motor. How that works is not obvious, so I was explaining what that was about.


    Current = torque is only true until you hit saturation at which point it changes to current = heat, with zero increase in torque.

    Driving steppers is a complex subject and can not be covered properly in a few lines.

    Since you seem to have a quite a bit of knowledge, maybe you can help me understand the odd waveforms I'm getting from some STMicro driver chips:

    http://www.cnczone.com/forums/steppe...1-drivers.html

  8. #8
    Member
    Join Date
    Jun 2010
    Posts
    3923

    Re: Too much voltage?

    But beyond a point extra voltage gives diminishing returns and just produces more heating in the driver.
    Don't worry about it. Let the driver worry.
    DO make sure the driver is rated for whatever voltage you have. Got 60 VDC and the driver is rated for 80 V? Fine. Other way around? Dead driver.
    Then set the current limit on the driver for the rated current for the motor - or maybe a bit less.
    Enable 'current reduction when motor idle' if available.
    If the driver you have is antique and does not mention these features, buy a new driver. Seriously.

    Cheers
    Roger

  9. #9
    Registered
    Join Date
    Jan 2018
    Posts
    12

    Re: Too much voltage?

    Where does one find 60v power supplies? I have not found a decent price from a reliable source.

  10. #10
    Member
    Join Date
    Jun 2010
    Posts
    3923

    Re: Too much voltage?

    If you are trying to buy a switched-mode 60 VDC power supply for the drivers on your CNC,
    DON'T
    It won't work.

    Buy a 40-42 VAC output transformer (a big one), a high-current diode bridge, and a large capacitor rated at 80 VDC or higher (or several of them). This combo should give about 60 VDc - unloaded it will be a shade higher than this.

    To explain: SMPS units may produce a fairly stable output voltage at high current, but most of them will also have a lot of noise on the output - RF interference type of stuff. This RFI will play merry hell with your drivers (if they are modern ones). Modern drivers are designed to work with very simple transformer/bridge/cap power supplies, and the doco will normally tell you this.

    Cheers
    Roger

  11. #11

    Re: Too much voltage?

    Quote Originally Posted by ShallowPass View Post
    Where does one find 60v power supplies? I have not found a decent price from a reliable source.

    I've had good luck with these guys https://www.automationtechnologiesin...ower-supplies/
    Jim Dawson
    Sandy, Oregon, USA

  12. #12
    Member
    Join Date
    Jun 2010
    Posts
    3923

    Re: Too much voltage?

    Jim is right! They would do.
    (Note the comments in the specs - clean unswitched power.)

    Cheers
    Roger

Page 1 of 2 12

Similar Threads

  1. Low Voltage vs High Voltage Stepper motors?
    By Brian_M in forum Stepper Motors / Drives
    Replies: 28
    Last Post: 06-21-2017, 07:29 PM
  2. Precix 9100 Controller - VI voltage issue Voltage range only 6.5 to 10Volts
    By wdysf150 in forum Controller & Computer Solutions
    Replies: 1
    Last Post: 09-08-2014, 07:50 PM
  3. Chopper drive max voltage vs max voltage of Nema23
    By K_G_B in forum Stepper Motors / Drives
    Replies: 7
    Last Post: 07-11-2014, 04:17 AM
  4. High voltage power supply, low voltage perihperals
    By feechl in forum General CNC Machine Related Electronics
    Replies: 2
    Last Post: 01-07-2014, 02:12 AM
  5. Help..Stuck at relay ext dc voltage missing but dc voltage OK ?
    By Dirky in forum Bridgeport / Hardinge Mills
    Replies: 24
    Last Post: 11-27-2007, 02:33 PM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •