Shunt Regulators

[janz99]

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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[CitizenOfDreams]

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.

[janz99]

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.

[Fastest1]

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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[109jb]

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.

[Fastest1]

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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[janz99]

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:

http://www.cnczone.com/forums/leadsh...estions-2.html

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

[Eldon_Joh]

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.

[CitizenOfDreams]

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.

[CitizenOfDreams]

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.

[janz99]

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.

[109jb]

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.

[janz99]

I think at this point, I am going to add the shunt regulator just to be on the safe side. I don't see it hindering the performance of the machine, and for $150, it will give me piece of mind. I emailed a few vendors and they have one of the 3 shunts that Leadshine has recommended in the documentation I linked above.

[Al_The_Man]

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.

If you want a true E-stop then the correct way is a small hard wired control relay that has all the necessary stop functions in series or (N)AND'ed in its coil circuit, it is a combination of the selection of circuits on p6 p7 in this link.
The items in the string would, of course be, apart from E-stop P.B.'s, any L.S. or the output of the a Mach charge pump etc, a contact on the control relay would switch any main contactor coil or power supply source that controlled motors.
Everything else stays energized, just any motor driven or any device that can cause injury in the event of a machine failure etc.
The charge pump also holds off any premature energization of the control relay until the P.C. has booted and the Mach Emergency reset.
http://static.schneider-electric.us/...0140CT9201.pdf
The only thing incorrect with the PDF circuits is that now it is a no-no to place the overload on the common or neutral side of the relay coil, if fitted, it should be in the main string.

P.S: A contact on the control relay can also input a E-stop to inform Mach etc, that a external E-stop has taken place.
Al.

[naspc]

@janzz99
Which Shunt regulator did you end up getting?

[naspc]

@janzz99
Which Shunt regulator did you end up getting?

I started some of my research. I ended getting one from advance Motion Controller SRST70.

1. Advance Motion Controller SRST50 $100 + $9.36 shipping
2. Advance Motion Controller SRST70 $100 + $9.36 shipping
3. Called Leadshine talked to Chris Li, he said "either of the 2 (listed above) will do. They can be adjusted"
4. Maxon motor DSR70/30 looks to be $399.98