G-251 acting loony tunes!!

[jhowelb]

With a new router build complete and all the electronics tested and after running several projects the machine was happily drilling anchor holes when the Z axis motor began buzzing rather than turning.

The Z axis driver now produces the same noise on any of the three motors and either of the other two drivers will spin any of the motors. I think this isolates the driver as the culprit but I can't for the life of me divine the cause nor the cure.

Can anyone make a suggestion?

[jhowelb]

The silence is deafening, not even an echo!

[CoAMarcus]

jhowelb,

Sorry for not getting back to you, but you posted at 3:30 yesterday which is when we are very busy around here because of shipping deadlines. Please send the drive back with the "Stepper Return Form" located on our website filled out. We will take a look at the drive and let you know what we find.

Marcus

[jhowelb]

Thank you.

[jhowelb]

Exactly what does "Current sense resistors were blow open which shorted the motor leads." mean? I can not avoid future problems unless I can understand the perceived problem.

[Mariss Freimanis]

Well, that's backwards.:-) The motor windings were shorted on terminals 7 and 8 or terminal 7 was shorted GND. The resulting short-circuit took out the top bridge MOSFET (drain to source <0.4 Ohms). This resulted in an unconstrained current through the bottom MOSFET and the 0.056 Ohm current sense resistor servicing that bridge. The resistor promply burned open. Once burned open, the lack of a ground path on the 2 bottom MOSFETs resulted in gate oxide rupture (drain to source = 5 Ohms). In all, 3 MOSFETs, one current sense resistor and two IR2104 half-bridge gate drivers were destroyed.

The G250 / G251 is unprotected against any shorts on its 4 motor outputs. Just like the G201 and G210, any short-circuit in any combination will destroy the drive. Mis-phased motor windings will destroy the drive.

The G540 protects the 4 G250 drives it contains by having a short-circuit protection circuit on its main board. It detects a short-circuit and acts quickly (3uS) to shut off all 4 drives before damage can occur (>100uS).

Mariss

[jhowelb]

As stated in post #1, all drives tested and secured and placed in secure closed box beyond SNAFU.

Cables are multifilament so not likely to break and were tested for internal shorts and found to be intact. The suspect motor cable (Z) was subsequently attached to X and Y drives which spun the motor merrily.


I am now flummoxed! Absent a failure of some component in the drive there seems no place for me to turn. (Is there such a thing as a stepper with intermittent short or open?)

I will install the replacement drive and use it till one of them fails then replace them with some 203V's I have on hand. The project I wanted to use them for will, in all probability, never happen in the face of the economy going South.

[see@see]

Mariss
Hope you do not have bad news for me here.
First off I have 3 g202s and I have them running great.
I am running 4 wire bipolar motors and the drives perform fantastic.
I purchased 2 g251s awhile back from you to retrofit a small cnc wood lathe.
I set one up today on my bench with one of the lathe steppers which are powermax 8 wire ,parallel 3 amps and series 1.5 amps.
I have them to what I believe and have read on the pacsi web site as series connection.
I have a C10 Breakout board that I am running off
after making all connections and also having a g202 setup with my bigger motors I started up mach 3.
now i see that the g251 requires a ground connection from the breakout board where as the g202 requires a +5 volts.
I am also using a 42 volt power supply at 18 amps.
I have a set resister on the g251 to not exceed 3 amps.
after all was set I powered up the drives and the small light on the drive lit up as well as the g202.
the g251 is on the y axis and when I hit the jog button in the up position the motor on the g251 moves although not to great.
when I push the button in the Y axis for the opposite direction the motor does nothing and actually the light on the drive goes out.
the g202 on the same setup runs perfect and sounds great.
I have not connected my second g251 drive yet and wont until i know
what my problem is here although I am starting to worry that maybe I have somehow hurt my drive.
can you please tell me what you think my problem is here.
And one thing mariss, I did have this smaller step motor running On the g202s with no problems.
Thanks mariss
Clint

[Mariss Freimanis]

They will have to be sent back for repair. Putting +5V on the G251 SIGNAL GND damages the drives.

Mariss

[see@see]

But Mariss, At no time did I ever put +5 volts to the g251, Only Ground.
I was just comparing the g251 and the g202 above, I was well awear of this long before I connected any wires.