Jump to content


Photo

Simostart Siemens Mv


  • Please log in to reply
10 replies to this topic

#1 trimar130

trimar130

    Junior Member

  • Full Member
  • PipPip
  • 5 posts

Posted 07 January 2008 - 07:28 AM

Dear All,

I'm new member in this forum, I'm Tri and currently working for BOC gases Indonesia in Jakarta

Does anyone here (esp to Mark) have experience about Simostart Siemens softstarter MV??

1) I've been succeed commissioning the sofstarter 250A FLA in November last year, and then the motor compressor 139A running for a week then stop. Setting softstarter: curve 1 (standard), current limit, initial voltage, stall time and max start time being set.

2) Unfortunately, when I need to re-start the sofstarter last week it could not work. which were fault message:

SET CURVE TO 0

when i set to curve 0, the fault message is different:

SCR SHORT OR WRONG CONN

3) I had test the fiber optic lead using microcontroller test; red lead and green light are okey
4) After replaced firing board, the fault message is different which is UNBALANCE. seeing that I2 is quite far from I1 and I3

Does anyone here have eperience to test the SCR and fiber optic cable?

Mark, I try to reach you via Skype but could not. do you have any yahoo messager?

Tri
+62-21-4601793





#2 marke

marke

    Posting Freak

  • Moderator
  • PipPipPipPipPipPip
  • 2,604 posts
  • Gender:Male
  • Location:Christchurch, New Zealand

Posted 07 January 2008 - 07:06 PM

Hello trimar130

Welcome to the forum.

Sorry I missed your attempted calls, we operate on a different time zone down here so you need to remember that.

The Simostart is not a soft starter that I am familiar with, but it is just a soft starter and if there is anything major, it should be easy to find.

The first and obvious question to ask, is have you been in contact with the local agents for support?

The messages that you got suggest that there may be an SCR issue.
This is easy to check, but you must be very careful and make sure that voltage is removed!!

If you take the covers off the three arm assemblies, you can get at the heatsinks. There will be two of more series SCR pairs per phase where each section is made up of two reverse parallel connected SCRs. These will have a voltage rating of between 3300 and 4500 volts. In order to control a high voltage, a number of these reverse parallel connected pairs are connected in series.
If an SCR has failed, it will almost definitely go short circuit and you can test each pair with a multimeter to see if there is a short circuited SCR. Check from one heatsink to the other for each pair.

Also check the bypass contactor input to output on each phase to check that this has not gone short circuit. I have experienced problems with vacuum contactors remaining closed.

If the SCRs check out OK, I would run the soft starter in test mode with a low voltage input, (400V or so) and a set of 100W+ lamps on the output. Use 230 V lamps if you use 400V input and connect the lamps in a star configuration. You should now see all lamps illuminate evenly when you call for a start. If one lamp is dull or slow, it will suggest that SCRs on that phase are not being controlled correctly. If one set jump to full brightness, then there may be a problem with that phase.
The instruction manual should tell you how to set the starter up for test mode.
If the lamps all work OK, then try with a small 400 volt motor, say 5 - 10KW and if that is all OK, you should be able to go back to the MV set up and run OK.

The advantage of using the low voltage test, is that you can safely see what is happening.

Best regards,

#3 jraef

jraef

    Posting Freak

  • Moderator
  • PipPipPipPipPipPip
  • 683 posts
  • Gender:Male
  • Location:USA, California

Posted 08 January 2008 - 12:11 AM

The Simostart MV was not actually manufactured by Siemens, it was brand labeled from Solcon out of Israel. Siemens discontinued the relationship with Solcon in 2003, partly (I heard) because of the problems they had with that digital controller. When I worked for Motortronics years ago we started off in the MV market by buying just the front end controller from Solcon. We had a lot of trouble with it being unstable as well, so we developed our own. In some parts of the world now, Siemens is marketing the 81000 Series Sikostart MV, which uses the front-end controller developed by Motortronics. You definitely have the Solcon version though.

The display reading of "Set Curve to 0" was a way of indirectly telling you that your settings are inadequate for a successful start. Curve 0 is the most basic starting set it has, no feedback, open loop voltage ramp. The reason they did that is because some of the other feedback and systems can mask a problem. If it can't start with that curve then there is a problem, which is what you are seeing when you then try again and get the "Wiring Error" indication. Although they say in the manual that it indicates something is wired wrong, that would only be valid at the initial commissioning. If it is happening after the unit has been running successfully, it is also what you get when you have shorted SCRs.

Possible causes:
One of the problems with the Solcon design was that they did not use a Line Isolation Vacuum Contactor ahead of the SCRs as a standard feature and failed to inform users that it needed one, probably in an effort to make it appear cheaper. Without one, spikes and surges from utility grids will often damage the dV/dt snubbers that are protecting the SCRs, then it's only a matter of time before the SCRs themselves become shorted. Once you replace the SCRs (and that will not be easy), I would recommend adding a line starter ahead of it if you don't already have one.

Another possible cause on compressor applications is a sticking relief valve. For instance, you commissioned the starter for an unloaded start with the valve open to vent to atmosphere until the motor was up to speed, but now the valve is failing to open and your starter attempted to start the compressor into a closed head, which is virtually a locked rotor. The fuses would not be fast enough to protect the SCRs from dI/dt damage.

If you don't have a manual, you can download one from here:
http://solcon.com.mx...es/HRVSDN-I.pdf
"He's not dead, he's just pinin' for the fjords!"

#4 trimar130

trimar130

    Junior Member

  • Full Member
  • PipPip
  • 5 posts

Posted 08 January 2008 - 04:33 AM

thanks for mark and jraef for the fast response,
a lot of new thing here as per reccommendation from both of you

How does if any UNBALANCE fault message occured? Is it possible caused by SCR firing system?
We've also found that phase S (I2) is lower/ not balance with phase R(I1) and T(I3).
Or is it possible being caused by the power transformer unbalance and drop when we starting the motor?

since beginning of commisioning I'm being supported by siemens local, but no good result yet
tomorrow there will be another guy from Siemens Singapore also will bring spare parts with him

About the motor and compressor, I've checked the motor (megger, microohm, and surge) the result is okey.
And compressor inlet valve and venting valve already tested and okey also.

will update you if any progress.

Regards,
Tri


#5 jraef

jraef

    Posting Freak

  • Moderator
  • PipPipPipPipPipPip
  • 683 posts
  • Gender:Male
  • Location:USA, California

Posted 09 January 2008 - 01:07 AM

QUOTE
How does if any UNBALANCE fault message occured? Is it possible caused by SCR firing system?
We've also found that phase S (I2) is lower/ not balance with phase R(I1) and T(I3).
Or is it possible being caused by the power transformer unbalance and drop when we starting the motor?


Unbalance is another thing that may be the result of a shorted SCR on a MV soft starter.

To understand better, let me explain how shorted SCR detection works. SCRs have a voltage drop across them when functioning normally, roughly 1-1/2V. In Low Voltage soft starters where you have 1 SCR in each 1/2 phase, it is relatively simple to detect if one of them is shorted, you simply monitor the voltage drop across the stack (inverse parallel pair) and if it is less than 1V, it must be shorted. But Medium Voltage soft starters need to be built differently. In order to attain the voltage rating necessary, SCRs are put together in series strings on each 1/2 phase, so for a 3300V starter you will have 2 or 3 SCRs in series with each other, but you also have a single snubber network across the entire string. As a result, you cannot really tell if one of the SCRs is shorted, only if ALL of them are shorted. So even though the soft starter says it has "shorted SCR detection", it cannot really tell if only one or a few SCRs are shorted. The designers know that, so they build in other protection features to pick up on the EFFECTS of having only 1 or a few shorted SCRs, such as "Unbalance", "Wiring Error" etc. Chances are very high that this is what you will find.

It is however conceivable that you have a problem in your supply power. Not as likely, but it is possible that under starting stress, your transformer (or one of the connections) is dropping voltage on one phase.
"He's not dead, he's just pinin' for the fjords!"

#6 trimar130

trimar130

    Junior Member

  • Full Member
  • PipPip
  • 5 posts

Posted 11 January 2008 - 01:38 AM

I have checked the power transformer, and the result was good.
Start the softstarter and compressor with 30%-inital voltage then trip at 8s with fault message unbalance. on the display microcontroller saw that R: 400A, S: 270A, T: 380A. unbalance setting is 20%.

When we tested sofstarter with small fan 18.5kW, 380V, we monitored the phase R,S, and T. All of three phases were balance.

Then we increase the inital voltage to 40%, and re-start the compressor with others paramater setting were same. "Long Start Time" happen in 23s because we limit the time at 22s.

We confused wacko.gif why setting 30%-inital voltage the fault was unbalance; and with setting 40%-initial voltage the unbalance was passed. Could anyone explained about this?

What is the meaning by acceleration time???
does it the time that ALLOW sofstarter from initial to full voltage (pasive).....or does it the time which softarter GIVE ORDER to make the system from initial to full voltage (active)??

Tri
+62-(0)-813-10322324


#7 jraef

jraef

    Posting Freak

  • Moderator
  • PipPipPipPipPipPip
  • 683 posts
  • Gender:Male
  • Location:USA, California

Posted 11 January 2008 - 04:08 AM

That is one of the problems we (when I worked for Motortronics) didn't like about the Solcon digital controller. It is an "interrupt driven" system with the microprocessor doing the direct firing control of the SCRs and because of scan time, has trouble with stability at low firing angles (specifically 30% and down). It would lose control of the feedback signals and the firing pattern of the SCRs would become erratic. Most of the time there is no point in having a firing angle that low anyway but occasionally it would crop up, as it has for you.

But do you really need it to be that low? Most of the time, an initial voltage below 50% is not going to do any useful work and just serves to warm up the motor needlessly, especially on something like a compressor. If the higher level works for you, leave it at that. The initial torque (voltage) level should not be any lower than will make the rotor begin to move.

The "Acceleration Time" is a feature meant to protect your motor from a stall during soft starting. The time limit should be coordinated with your motor's thermal damage curve and any starts-per-hour limitations you may have. It is the total "Starting Time" from when you give it a Start command to where it detects that the motor has reached full speed. It detects full speed by a combination of the voltage firing angle being 100% and the motor current having gone above 100% and back down again. If the motor current never drops even though the voltage is fully on, AND the timer has expired, it trips.
"He's not dead, he's just pinin' for the fjords!"

#8 trimar130

trimar130

    Junior Member

  • Full Member
  • PipPip
  • 5 posts

Posted 11 January 2008 - 11:33 AM


That is one of the problems we (when I worked for Motortronics) didn't like about the Solcon digital controller. It is an "interrupt driven" system with the microprocessor doing the direct firing control of the SCRs and because of scan time, has trouble with stability at low firing angles (specifically 30% and down). It would lose control of the feedback signals and the firing pattern of the SCRs would become erratic. Most of the time there is no point in having a firing angle that low anyway but occasionally it would crop up, as it has for you.

<Tri> You said that this unbalance was happen due to micro controller and lose of feed back signal. Didn't you?
and when it is true, what is the mitigation to prevent this occassion re-happen again in the future?

Today we already succeed start and running the compressor, setting as follow:
initial v: 40%
max start time: 24s.
while compressor started the ampere of phase R: 440, S: 440 and T: 440.

After a half hour we stopped the compressor and then re-started to ensure the setting is correct.

Unfortunately the unbalance was occured. R:440, S: 370 and T:460.

Regards,
Tri

#9 marke

marke

    Posting Freak

  • Moderator
  • PipPipPipPipPipPip
  • 2,604 posts
  • Gender:Male
  • Location:Christchurch, New Zealand

Posted 11 January 2008 - 08:15 PM

Hello Tri

In some designs, there are issues if you have a start voltage less than 50%. This is not the case in all designs, but in reality, it should not be an issue because you will almost always need to have greater than 50% voltage to start a machine anyway.
As you reduce the start voltage, you reduce the start torque by the voltage reduction squared. So at 50% start voltage, the start torque is reduced to 25% of the full voltage start torque.
If the start torque is too low, the motor will not be able to accelerate the load to full speed and you will overheat the rotor.
When you use a voltage ramp starter, it is important to set the start voltage high enough so that the motor begins to spin up freely the moment that the power is applied. If the motor is straining to turn the load and not accelerating freely, the the start voltage is too low.

In this case, you are quoting a start time of 24 seconds. That seems much to long to me. If you increase the start voltage, you will shorten that time and probably will not increase the maximum start current. I would expect the start time to be closer to 10 - 12 seconds than 24.

Have a try at 50% voltage or even possibly 60%.

Best regards,

#10 trimar130

trimar130

    Junior Member

  • Full Member
  • PipPip
  • 5 posts

Posted 12 January 2008 - 03:20 AM

thanks marke,

Please see my first email, which is point no:

1) I've been succeed commissioning the sofstarter 250A FLA in November last year, and then the motor compressor 139A running for a week then stop. Setting softstarter: curve 1 (standard), current limit, initial voltage, stall time and max start time being set.

==> at that time the initial voltage setting was 55%. Current limit 310% and max start time 26s (we are being limited by power transformer capacity and its protection)
While we re-started using curve 0 at that setting, the incoming electricity (PLN) trip due to ground fault and un-balance on the phase S.

Say that setting initial v=55% was succeed, and also setting inital v=40% was succeed.

What my problem now is the UNBALANCE that not always occured. With the same setting, sometimes it was happen and sometimes it was not. When it was occured, always more than 20% higher than setting. And twice I trip the PLN supply electricity due to its protection graound fault.
Please note that we already checked the motor and power transformer, both are okey.

Is there any Solcon's Guy here?? Please kindly to help me about the microcontroller issue by Jraef.

Regards,
Tri



#11 marke

marke

    Posting Freak

  • Moderator
  • PipPipPipPipPipPip
  • 2,604 posts
  • Gender:Male
  • Location:Christchurch, New Zealand

Posted 12 January 2008 - 11:37 PM

Hello Tri

It sounds like you are getting an erratic behaviour which is not predictable.
Unfortunately, this is probably due to the algorithms used in the design of the software and there is litle that you and the end user can do about this.
As previously mentioned, there can be issues with some soft starters when the start voltage is too low. Increasing the start voltage will commonly overcome these problems. There are also some soft starters that are affected by the supply impedance. If the supply impedance is high, then the action of the SCRs can introduce distortion on the supply voltage and this in turn can cause the micro software to become confused and the SCRs can be incorrectly controlled. This can also be improved sometimes, by increasing the start voltage setting.

Unfortunately, the only thing that I can suggest is to try a higher start voltage setting and see if the problem goes away, and/or put pressure on the supplier to sort the problem out.

It is possible to design units that do not have this problem, but it is difficult/impossible to fix a bad design in the field.

Best regards,




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users