ACS 800 fault # 4380 - TEMP DIF 3 U

This post is about fault number 4380 TEMP DIF 3 U. Long history short: clean your air filters. Other cause that I can think of is a hot spot on the connections on top of the modules. Good luck!

To give a little bit of context it must be said that underground mine environment has -despite control measures- presence of dust, humidity and fume due to other equipment operations, ventilation system airflow and others. Additionally, mining is a dynamic activity where you can see your quiet working space transformed into an area fully packed with workers and equipment (and their pollution) in just a couple of shifts.

This was how we ended experiencing fault 4380. An increase in pollution in the area where our beloved ACS800 drive works led to a clogged air filter despite we clean them monthly. Temperature got above failure threshold and voilá there was a new failure what to post about. Afterwards we decided to clean air filters quarterly and so far it is giving good results.

                     4380 fault message 

                          Air filter clogged 

ACS 800 F081 EMS STOP FAULT

The F081 fault was showing at the drive panel. It didn't show a regular pattern since it occurred both during movement of skips and when they were stopped at discharge position.

Figure 1. F081 fault.

First day we of course started by checking all emergency push buttons in the drive, PA console, at the LD and LL panels. Nothing wrong here and fault still happening.

Second day we checked drive inverter modules since Drive Windows' fault log showed a START INHIBI fault. This fault is (according to the manual) is linked to the ASTO control board. We check the drive modules and cleaned them up but fault still happening.

Figure 2. SYSTEM START fault

Figure 3. START INHIBI fault.

We finally checked PA.1 fault log again. We noticed that it showed a list of faults that are not really linked each other in the field. Kevin (one of the electrical guys here) then found a diagram that showed most of the components in the fault list. It was the one that shows connections of power sources at the AHC panel. We switched them off and voilà! we got same fault list. New power sources were installed and there was no problem since then. So please consider to change or upgrade your power sources every 4 years.

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Figure 5. New power sources installed.

ABC. 1 GP1 Valve 57 flt

This post is about "ABC.1 GP Valve 57"  fault and how we solved it . 

Fault has been occurring ever since we started operations but it didn't happen often so we didn't do further research until it hit us twice in a week causing my boss to panic and ended giving me the task to find the root cause of the fault.

Figure 1. The very moment when fault occurred.

In this particular case the fault occurred due to operation of the selector switches at the control panel PA.1. This happened because the placement of two switch selectors (clutch mode switch and operation mode switch) in the operator panel were side to side making possible for the operator to make the wrong selection. Usually the attention of the operator is focused on the CCTV monitor or in the HMI panel.

Figure. Usual operator posture

Figure. Original placement of switch selectors in control panel PA.1. Clutch mode and Operation mode switches are in the middle side to side.

Figure. New placement for switch selectors. Now "Clutch Mode switch" and "Operation Mode switch" are as far as they can be. It makes hard for the operator to get the wrong switch.

Additionally, due to the research done, other causes for this fault were found:

* Inductive sensors in valve 57. This is the first thing we inspected since it is linked to the description at the fault. We checked wiring connections and we watched the functioning during hoist operations.

Figure. Inductive sensors at v57 valve in GP.

* Clutch and sprag limit switches. Somehow during investigation somehow moved one of the limit switches at the clutch mechanism and this v57 fault appeared. Then we tried the same with the sprag limit switch and gave us the same result. I wonder that if these limit switches are loose you may have this fault too.

Figure. Manipulation of clutch limit switches.

Figure. Sprag limit switch.

ACS 800 Supply phase error

Here a "quick" fix if you are having this error message. Accumulation of dust and dirt inside modules creates DC bus distortion which makes the ripple value to increase near or above 13% threshold. This situation gets interpreted as a phase loss since in this case ripple increases too.

Supply Phase error message description. Taken from ACS800 Firmware manual System Control Program 7.x (3AFE64670646 REV G), ABB, 2011

So, first step is to check if you are experiencing a phase loss. You can do it by using the voltage meter on the door of the ACS800. If all three phases are ok well then it is time to clean your modules! but... How to know where to start? Easy, check out DC bus behaviour through Drive Windows for every stage (rectifier, inverter) and you will be able to spot where to start. Now it is time to give a call to your supervisor and notify that this make take a little while (1-2 hours in my experience). Before starting with the cleaning activity please remember to deenergize and apply your LOTO procedures.

DC bus before (yellow) and after (red) cleaning.

Some extra considerations:

• Be careful with fibre optic connections to the modules. They may get damaged if you pull the modules without disconnecting them first. It sounds hard to happen but it does.
• Use the metal ramp to remove the modules considering ABB safety instructions. 
• Use support legs of the module to prevent it from falling since its centre of mass is in the upper half of the module.
• Consider to measure DC bus in a regular basis. It helps to see how it changes over time so maintenance activities are scheduled before failure.

Using module's support legs.

ACS 800 encoder error #7301

Here at my job we have an ACS800 multidrive to control speed and torque of the hoist motor. This post is about the error code #7301 "encoder error" and the adventure it was trying to tackle it. This is done with the aim that some of the information here may be of good use to anyone dealing with this error.

First of all, if you are reading this in desperation because the encoder error trips your winder, here I have great news: you can change the error status from FAULT (default setting) to ALARM. It can be done using drive Windows software or through the keypad as well. Doing this will give you the extra time you need to perform troubleshooting without delaying / stopping operations. Off course, to take this decision you first have to evaluate it doesn't compromise safety of operations.

Here are the steps to follow when using Drive Windows:

1. Connect to drive.

2. Open parameters window. Go to parameter 50.

3. Double click on encoder. A little window will pop up where you can choose error status to be FAULT or ALARM. Click on ALARM then click OK and that's it.

Additionally, you may like to visit the following links since they may give you ideas about how to perform troubleshooting. It worked for me.

Link 1: ABB Forum
Link 2: Engineering tips

Now, this is my adventure with encoder error #7301...

This error has been showing up occasionally since the hoist commissioning (once per month as much) but lately it's been occurring more often (1 or 2 times per day) so we decided to allocate some time to check up the reason for this fault to occur.

Error 7301

According to the ACS800 troubleshooting, this error requires to check encoder wiring. Specifically the one attached to the motor's back since its signals go from the encoder to the AHC panel and then to the RTAC module at the drive control cabinet. 

So we did it, Wiring and connections were checked and tightened. We got a couple of days error free but then it started to show up again and -lucky we- it happened at peak hour. We changed the error status from FAULT to ALARM to give us chance to finish the shift and continue with troubleshooting.

Wiring check up at both ends and through cable tray

Next steps were made to determine which element was causing us headaches:

* Change encoder: no results.

* Change of Isolation amplifier card PE1315A at AHC: No results.

* Change of RTAC module: Error free for a week then it started again.

* Change encoder wiring from encoder to junction box: no results. Here we noticed that motor cover was deforming the wiring so we asked our mechanical people to modify it as a preventive measure despite it was not the cause of the fault.

* Change of encoder wiring from junction box to AHC panel: no results.

* Change of encoder wiring from AHC panel to RTAC module at drive: Eureka! We believe this wiring was damaged during installation.

Shaft guide alignment using a decelerometer

I work in an underground gold mine in the north of Darkest Peru. The company has recently commissioned an 800 metres long vertical shaft with the purpose to transport personnel, material and waste. It has four compartments, two for skips and other two for a cage and its counterweight. Since it was a new shaft we thought everything was in good working conditions but it wasn't the case because we found that there were friction between skips and their metallic guides in several locations along the shaft. This was causing rapid wearing of skips' roller guides (We had one roller guide completely worn out after just three days). There even were some places where friction was strong enough to produce sparks.

This situation frightened the mine's management people so experts were hired to look at this problem. Few days later we got the visit of two guys from Tiley Associates who performed a shaft guide alignment test using a decelerometer. The idea of the test is to correlate acceleration measurement vs shaft's depth. Places with high acceleration measurement are an indicator of guide missalignment. The following criteria is used to determine wether the situation is critical or acceptable.

• Critical guide missalignment: acceleration measurement is greater than 0.5g or lower than -0.5g. Requires to take immediate corrective action.
• Bad missalignment: acceleration measurement between -0.5g and -0.25g or between 0.25g and 0.5g. Corrective action should be scheduled during the next planned maintenance.
• Acceleration between -.025g and 0.25g can be taken as acceptable missalignment.

Note 1: This criteria is valid under the consideration that shaft's structural integrity is in good conditions. 

Note 2: g=9.8m/s2.

Our technicians used the information from the Tiley report to improve guide alignment and results started to show immediately: Smooth cage and skips movement, no sparks and a significant reduction of guide rollers wearing. With these results in mind, our company decided that alongside periodical Tiley assessment we should perform an internal assessment more often so any problem can be spotted while it is in its early stages. For that to be done a decelerometer has been bought. In matter of weeks we developed a template in excel that uses raw input data from decelerometer and shows acceleration vs depth which is valuable information when performing shaft inspection.

Raw data from decelerometer is given in the following format:

Station_code    GMS
Sampling_rate   50.000000
Start_date      23.05.2018
Start_time      18:10:35.000
Time:sec   X0HNE,g    Y0HNN,g    Z0HNZ,g
0.0000000000e+00 6.7869942000e-04 6.1697539000e-04 4.8637476000e-04
2.0000000000e-02 6.2969107000e-04 6.0955791000e-04 5.4756897000e-04
4.0000000000e-02 5.9445804000e-04 6.0002115000e-04 5.5737064000e-04
6.0000000000e-02 7.1790610000e-04 5.6717231000e-04 5.1789905000e-04
8.0000000000e-02 7.4996021000e-04 5.8041781000e-04 5.1339558000e-04
1.0000000000e-01 6.1141228000e-04 5.5710573000e-04 5.6372848000e-04
(...)

First 4 rows show information of the station, date, time and sampling rate. From the 5th row we can notice withdrawn data from the station: Time vector and gravity acceleration in X, Y and Z axes.

g vs depth graph

X and Y axes give information about lateral movement of skips along the shaft while Z axes provides vertical acceleration. Speed and position can be obtained by integrating and double integrating acceleration values. Some help and guidance can be found in this Wikihow post.

Knowing alignment conditions beforehand allowed us to do inspections in less time and saved us thousands on rollers replacements so implementing this activity is highly recommended.

Nanosecond pulse generator

Well, where to start... A nanosecond pulse generator is used as part of an experimental space charge measurement equipment developed at the UNSW's High Voltage Laboratory. The required output must provide not only a narrow width (less than 15 ns) but also a magnitude that exceeds 200 V (the goal was 500V). Most of the literature available regarding nanosecond pulse generators is related to biomedical applications, e.g. Sanders et. al, [1] have developed a pulse generator to deliver electric fields to biological loads in order to produce cellular membrane  electropermeabilization. Pulse generators of this type (relatively high magnitude, short duration) are being used in other applications within four major categories [2]: 

• Industrial: food processing, concrete recycling, plasma systems.
• Environmental: ozone generation, waste water treatment.
• Medical: electroporation, plasma medicine.
• Military: laser guns, electromagnetic launchers, radars.

Nanosecond pulse generators are available in the market but they are yet expensive, especially for research and educational activities. The cost of a single pulse generator with the required characteristics can go well beyond 4000 USD. AV Tech pulse, FastPulse technology Incorporated, Yamabishi Corporation, FID GmbH are among the companies specialized in providing this type of equipment. 

Some of the most important topologies are:

1. Diode opening switch (D.O.S): this topology generates a clear and well defined pulse, however the calculation of the components is complex as well as its implementation since it depends on several parameters such as the reverse recovery time of the diode, the MOSFET’s linear behaviour and the spurious triggering in the PCB layout [1].
2. Marx Bank based pulse generators: They are usually big in size and their implementation require spark gaps that may lead to high jitter. There is a variation of the topology called miniaturized Marx Bank which use transistors instead of spark gaps [3].
3. Transmission line based pulse generators: self-matched transmission line Blumlein [4] provides fast rise time and a square shaped pulse [5].

The first topology had been chosen due to its simple circuitry and was successfully implemented by Wu Chao [6] based on the work exposed in [1]. My first task was to make copies of the existing pulse generator but changing the pulse width in order to see if the pulse width has a significant impact on the measurement results. Unfortunately, Wu Chao had already graduated by the time I was doing this project so I had no have chance to bother him with questions. After reading his work, I decided to simulate the circuit using LTSpice, this was crucial for me to understand how this topology works so I think it is worth to share it. It does not have the same components used at the end but it gives a good approximation of the result. The main component is the diode D1 since the pulse width and the selection of C1,C2,L1 and L2 values depends on the reverse recovery time of the diode [1].

Simulation circuit of the pulse generator using LT Spice. Stop time=0.1s.

Simulation result of the pulse generator circuit using LTSpice. The pulse output can be noticed in blue in the bottom panel.

After few weeks, a couple of pulse generator boards were made, they are capable to provide a pulse width of 13 ns (full maximum half width method) with a magnitude of 250 V.

Pulse generator boards. Courtesy of  UNSW's High Voltage Laboratory.

Pulse output. Courtesy of  UNSW's High Voltage Laboratory.

References

[1] J. M. Sanders, A. Kuthi, W. Yu-Hsuan, P. T. Vernier and M. A. Gundersen, “A linear, single-stage,nanosecond pulse generator for delivering intense electric fields to biological loads,” IEEE Transactions on Dielectrics and Electrical Insulation, vol. 16, pp. 1048-1054, 2009.

[2] S. Zabihi, Flexible high voltage pulsed power supply for plasma applications, Brisbane: Queensland University of Technology , 2011. 

[3] M. Inokuchi, M. Akiyama, T. Sakugawa, H. Akiyama and T. Ueno, “Development of Miniature Marx Generator Using BJT,” IEEE Pulsed Power Conference, pp. 57-60, 2009. 

[4] S. Romeo, C. D’Avino, O. Zeni and L. Zeni, “A Blumlein-type, Nanosecond Pulse Generator with Interchangeable Transmission Lines for Bioelectrical Applications,” Transactions onDielectrics and Electrical Insulation, vol. 20, no. 4, pp. 1224-1230, 2013.

[5] G. Peng, Design of a modular high voltage nanosecond pulse generation system, Sydney: The University of New South Wales, 2013.

[6] C. Wu, Space Charge Measurement in Solid Dielectrics, Sydney: UNSW, 2012.