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| Thread ID: 87744 | 2008-03-02 12:38:00 | 3 phase power | motorbyclist (188) | PC World Chat |
| Post ID | Timestamp | Content | User | ||
| 645669 | 2008-03-03 09:54:00 | When you say "Engineer", do you mean Mechanical or Electrical? PJ | Poppa John (284) | ||
| 645670 | 2008-03-03 09:57:00 | I dont think it is an earth spike problem. In your fuse board the Neutral & Earth bars will be hard linked with a brass strip. The main neutral & the main earth (down to the earth spike) would be on the same neutral stud. So there should be NO potential difference between the earth & the neutral. The neutral is the earth & the earth is the neutral. The neutral will be bigger than the earth wire anyway & so will carry any fault current better than the earth. They go to the same point on the supply transformer anyway. PJ ah thanks When you say "Engineer", do you mean Mechanical or Electrical? PJ electrical i assume.... might ask the boss (dad) |
motorbyclist (188) | ||
| 645671 | 2008-03-03 10:01:00 | If the m/c nameplate says 400v then 390 is not a problem. PJ Assuming that the 390 does not become less when the m/c is working. There is a point where the voltage will be so low that controls will not operate. For instance, a contactor/relay coil will "Let Go" because of low voltage. I belive, when I worked in Auckland, that the Power Board was allowed a Low Voltage of no more than 10%. PJ |
Poppa John (284) | ||
| 645672 | 2008-03-03 10:07:00 | Another thought comes to mind. Dirty power supply. We had a problem where the newer computer controlled packaging m/cs would malfunction. Short story. We put a computer type voltmeter across the lines. It found "Spikes" so large & vicious that got thro the factory 11kv/400v transformer. That is what was causing our problems. These spikes were coming from new equipment at a nearby factory. The AEPB sorted that out. Turned out that we wernt the only ones being affected. PJ |
Poppa John (284) | ||
| 645673 | 2008-03-03 10:16:00 | we don't know if any nearby businesses have the same problem, but doubt it as not many of them have the sort of machinery we use. the machine is question is an older italian cnc cutting laser. we have a newer german one in the next building but that doesn't seem to have any problems, but it has alot of gear between it and the mains to make sure of that. the failing laser doesn't.... it has been worst between 8am and 4:30pm, which is why i have been suspecting the power supply i don't know about input transformer, but looking inside the most prominent parts are the HUGE capacitors and step-up transformers (up to 36KV i am led to believe) it had been giving occasional trouble in the past, but since last monday it's been un-usable. apparently a truck downed some nearby power lines during the previous weekend - so another reason to suspect the power late last year when it gave trouble we had a monitor put on, and nothing was found to be wrong with the supply, and then it went ok. the engineers looking at it now are still unsure of the root of our problem. they were looking at feedback through the earth (probably part of our problem), possibly damaged capacitors, wiring, corrupted software data.... asfaik still no joy most common failures relate to the table motor/controllers failing for whatever reasons, but it seems to only happen while the laser beam is on - ie, drawing a serious amount of power. poking around with a multimeter and looking at the wiring diagrams, a voltage output sent to the table determines the engine speed, but the motors seem to be getting out of step with the computers and causing it all to emergency shut off. occasionally the whole system will just drop it's program and sit there waiting for intructions, but that's pretty rare. unfortunately the error codes our diagnostic cards give us mean nothing as we don't have any manuals for them :( all we can do is reset the table axis (plural) that fail and start again Your paragrahp 6... You recently had a truck/power pole problem. The m/c problem seems to happen when you are using"Serious Power". To me that suggests low voltage when under Serious Power, (are you trying to get a quart out of a pint pot? so to speak?). What has the Power Board done recently? PJ |
Poppa John (284) | ||
| 645674 | 2008-03-03 10:31:00 | bugger all, that's what i'll ask at work |
motorbyclist (188) | ||
| 645675 | 2008-03-03 20:05:00 | PJ is on to it but remember your Voltage Readings should be taken under Full Load . You may need someone with the right monitoring gear to check this as the fault appears to be intermittent . But, going right back to basics, check if any electrical connections appear to have ever been hot . An intermittently high resistance (including loose) joint can cause this sort of problem but signs of heat or arcing can be the giveaway |
B.M. (505) | ||
| 645676 | 2008-03-03 21:07:00 | I'm no expert on HV power/Italian CNC laser mills, but have you tried ringing the power company? They may be having problems of their own. Also, with the timeframe taken into consideration, it sounds like the truck downing the lines reduced the capacity of the power grid in the area, and the machine playing up is the result of a slight brownout. But I'm no expert. | ubergeek85 (131) | ||
| 645677 | 2008-03-04 01:25:00 | I'm no expert on HV power/Italian CNC laser mills, but have you tried ringing the power company? They may be having problems of their own. Also, with the timeframe taken into consideration, it sounds like the truck downing the lines reduced the capacity of the power grid in the area, and the machine playing up is the result of a slight brownout. But I'm no expert. This is my feeling as well. PJ |
Poppa John (284) | ||
| 645678 | 2008-03-04 04:55:00 | The network company (sorry PJ, Power Boards all disappeared in 1994-1998) are allowed 230v +/- 6% at the main switchboard. 390v is well within the range allowed. | godfather (25) | ||
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