Shunt Regulators


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    Default Shunt Regulators

    Hey guys, I have an MX4660, and was told by leadshine that I should be using a shunt regulator. I am still waiting to hear back from them, but I was curious if any of you are currently using one? If so, what size/manufacture are you using? I am not familiar with shunts, I get their purpose but as for sizing one properly I am at a bit of a loss. Any suggestions or recommendations would be appreciated.

    Thanks,
    Ryan

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    Registered CitizenOfDreams's Avatar
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    Default Re: Shunt Regulators

    What size motors are you using and what is the supply voltage? Judging by the word "benchtop" in the forum's title, I suspect you could get by without a shunt regulator.



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    Default Re: Shunt Regulators

    Steppers are 906 and 570oz, power supply is 50 volts. Apparently when using an E-stop, there is some voltage/current being back fed? This has been known to kill drivers within the mx4660. They recommended a shunt regulator and a couple caps to prevent this.



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    Default Re: Shunt Regulators

    I run those same steppers on my G0704. I have run them with the MX3660? I did blow out a driver once (actually the SMD fuse). I always suspected it was due to me unplugging the drive before the power had dissipated.
    I haven't ever used shunts nor did anyone specify it. Not saying they don't. I was one of the first running that drive.


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    Default Re: Shunt Regulators

    Quote Originally Posted by janz99 View Post
    Steppers are 906 and 570oz, power supply is 50 volts. Apparently when using an E-stop, there is some voltage/current being back fed? This has been known to kill drivers within the mx4660. They recommended a shunt regulator and a couple caps to prevent this.
    The manual for the MX3660 shows a direct connection with no shunt regulator. They simply recommend using a power supply of 54V or less to account for back EMF from stepper deceleration.



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    Default Re: Shunt Regulators

    Which is exactly how I have it powered.
    Does it show differently on the 4660? They are the same units basically just an extra drive.


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    Default Re: Shunt Regulators

    This was Leadshines response when I had inquired about it: I sent him the link to the power supply that I had ordered.

    High-Torque Stepper Motor, Stepper Motor, Driver, Stepper Motor kit, DC Servo Motor, DC Servo Motor kit, Stepper Motor Power Supply, CNC Router, Spindle, and other Components. Stepper Motor | Stepper Motor Driver | CNC Router | Laser Machine | 3D Prin

    "I recommend you to use a shunt regulate ,since the cap is not good for reducing back-emf value ."



    EDIT: I just found this documentation posted on this forum from Leadshine. Go to the second page of this thread:

    MX4660 Power questions

    On page 8 of this documentation it gives you a few shunt regulators that should be used.

    Last edited by janz99; 08-05-2016 at 04:44 PM.


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    Default Re: Shunt Regulators

    so interestingly, their math is wrong.

    when calculating the additional energy dumped into a capacitor already charged to 48 volts, you must use the difference of squares to calculate the voltage its going to head to. so if 2 joules will charge your cap to 50 volts, if its already at 50, then it will charge it to about 67 volts.

    it would not surprise me if many have blown their drive because they had the E stop wired to disconnect the stepper driver from the power supply.



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    Default Re: Shunt Regulators

    Quote Originally Posted by Eldon_Joh View Post
    so interestingly, their math is wrong.
    it would not surprise me if many have blown their drive because they had the E stop wired to disconnect the stepper driver from the power supply.
    Strangely enough, I have seen people wiring their steppers through circuit breakers. Once I saw a really bizarre configuration where ONE of the stepper windings was wired through a breaker.



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    Default Re: Shunt Regulators

    By the way, what would be the "correct" way to E-stop a machine? Let's say we have a computer, a breakout board, a 48V power supply, 3 drives and 3 steppers.



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    Default Re: Shunt Regulators

    I believe with the 3660/4660 they have a specific e-stop output that you hook it up to. For machines without this, I'm not entirety sure what the correct way would be.



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    Default Re: Shunt Regulators

    An e stop that is wired such that it signals the computer controller to stop motion is in my opinion not a true emergency stop. I say this because it relies on software to stop the machine. A true e stop is independent and should stop all motion including the spindle.

    Having said the above, it is possible that the breakout board in the mx controller has a feature to disable the drivers, but even this is not what I would consider an e stop.

    The simplest e stop just cuts the incoming line voltage to the driver power supply, breakout board, and the spindle.

    You should never simply cut the power at a point between the power supply and driver, or between the driver and the stepper.



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