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Author Topic: WHATS THIS ERROR..??? Clearing a spurious limit hit latch event,  (Read 3722 times)

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Re: WHATS THIS ERROR..??? Clearing a spurious limit hit latch event,
« Reply #10 on: June 25, 2018, 02:40:06 PM »
Hi,
Steve's 100% if you have a VFD....don't use ordinary line filters, they wont work and may cause more problems than they solve.

Most manufacturers specify 'line reactors' on the input side of a VFD, not filters at all. Most manufacturers recommend NO output filtering on the output side UNLESS there
is a big (30m plus) cable run between the VFD and motor. Even then the filters are specialized....ordinary line filters will not do it.

Craig
My wife left with my best friend...
     and I miss him!
Re: WHATS THIS ERROR..??? Clearing a spurious limit hit latch event,
« Reply #11 on: June 26, 2018, 02:25:35 PM »
We use Line Reactors from Automation Direct and have had very good results. 

We filter our VFDs and Servo Drive input power through line reactors.

https://www.automationdirect.com/adc/Shopping/Catalog/Drives/AC_Drive_(VFD)_Spare_Parts_-a-_Accessories/AC_Line_Reactors
Chad Byrd
Re: WHATS THIS ERROR..??? Clearing a spurious limit hit latch event,
« Reply #12 on: June 26, 2018, 03:08:08 PM »
Hi,
in this instance OP is using a phase controlled bridge rectifier for a DC output. In that case line reactors are the exactly wrong choice,
excess line inductance makes it ever harder for SCRs to commutate. Ordinary line filters on input and output result in noise reduction
without designing specialist filters.
My wife left with my best friend...
     and I miss him!
Re: WHATS THIS ERROR..??? Clearing a spurious limit hit latch event,
« Reply #13 on: June 26, 2018, 03:15:11 PM »
Agreed, putting line filters between a SCR phase angle DC drive and a DC motor is not a good idea. Using a shielded cable could still be helpful.
Steve Stallings
www.PMDX.com
For PMDX product support, please use PMDX forum or direct email for quickest response. We do not use this forum as our primary product support site.
Re: WHATS THIS ERROR..??? Clearing a spurious limit hit latch event,
« Reply #14 on: June 26, 2018, 05:03:05 PM »
Hi,
I'm not so sure I agree with you Steve, I regularly put filters between a phase controlled bridge and
its DC load.

The input capacitance is typically less than 1uF and therfore the dV/dt current at AC line frequencies is
pretty modest. The capacitance is useful in reducing HF ringing on the DC output line.

One of my recent projects involved a phase controlled bridge delivering spot weld current, low voltage to be
sure but about 20kA! I fitted filters at the input of the transformer AND the output of the bridge. The inductor
was 95mm sq weld cable wrapped around a laminated core.

Craig
My wife left with my best friend...
     and I miss him!
Re: WHATS THIS ERROR..??? Clearing a spurious limit hit latch event,
« Reply #15 on: June 26, 2018, 05:24:55 PM »
I am confused. You stated that reactors could be a problem for SCRs trying to commutate. Line filters contain reactors (inductors) and would have this same effect. Perhaps it is a matter of the size of the inductor in a "filter" being smaller than a "line reactor"?
Steve Stallings
www.PMDX.com
For PMDX product support, please use PMDX forum or direct email for quickest response. We do not use this forum as our primary product support site.
Re: WHATS THIS ERROR..??? Clearing a spurious limit hit latch event,
« Reply #16 on: June 26, 2018, 06:29:08 PM »
Hi Steve,
exactly, line filters have inductances usually less than 500uH whereas line reactors in usually in excess of 5mH.

Line inductance causes the current to lag voltage, so as the current falls to near zero, the point at which the SCR would
commutate the voltage has already increased from zero. So just at the moment that the SCR has to establish its
reverse block its already under dV/dt stress.

Almost all VFDs have a rectifier/capacitor input which causes line current to be drawn in short duration high current pulses at the
peak of the voltage excursions. It causes current 'distortion' on the line, much to the power companies disadvantage.
Line reactors cause the pulses to be of longer duration and lower peak values with reduced current distortion. In many
cases the power companies will mandate that they be fitted on large installations.

While both line filters and line reactors are for the benefit of the electrical supply they address different technologies.

Craig
My wife left with my best friend...
     and I miss him!
Re: WHATS THIS ERROR..??? Clearing a spurious limit hit latch event,
« Reply #17 on: June 27, 2018, 12:04:22 AM »
shield ,shield ,shield ,both side inverter and motor
if you use pokeys hardware be sure you use the gndi not gnd
i used many controllers types in pokeys the noise problem are solve much faster than other thanks for that gndi
Re: WHATS THIS ERROR..??? Clearing a spurious limit hit latch event,
« Reply #18 on: June 27, 2018, 12:29:22 PM »
Its doing same error, without motor even powered on,...now
Re: WHATS THIS ERROR..??? Clearing a spurious limit hit latch event,
« Reply #19 on: June 27, 2018, 12:33:35 PM »
Its doing same error, without motor even powered on,...now
Whats gndi? I am using pokeys, is that gndi in pokeys or ess? Right now until i get problem figured out i got pokeys unhooked, i use pokeys for jog joystick, ground going to each pokey pin to activate joy stick axis,....but as i said i unhooked it til this issue is sorted out