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Hello, I have a wind turbine that is overheating on the rotor. The rotor consists of 60 separate electromagnetic coils, all connected in series. There is a separate DC circuit used to excite the coils. I have other machines that don't get hot, and they are using much less current to excite the...

Datasheet of the fan is attached. Rotation of the fan is correct and it doesn't appear to be slipping on the shaft (it's held in place by a grub screw into a keyed shaft). The dust extractor that the fan is blowing air into contains a number of "socks". These are basically a long tube of...

Hi, I have an inline fan that is being used for dust extraction. The fan is 1200mm wide with a 55kW motor (1400rpm). There is a cone/hood on the inlet side of the fan that is around 1m long and is slightly larger than the diameter of the fan (not sure exactly how much larger, around 400mm...

@badservo: I was starting to think the same thing - that this isn't a parity bit at all but some other way that the system is using to communicate with the devices (such as an address word, which indeed the first byte of data is). I will check the settings and come back to you (I am using...

Hey, I have an old software package that runs on MS-DOS. Needless to say it is tricky getting DOS to work on modern machines. So I had the bright idea of making a virtual machine of DOS and running it on a modern computer. This software talks to a number of machines via RS232 (actually it is...

I have very often had problems with the COM and USB ports not being mapped properly to the virtual machine. For example, say you have a USB to RS232 adaptor. When you plug it into your USB port it will map to the main computer, not the virtual machine. You need to configure your virtual...

Hi, Does anybody know the difference between DC surge protectors and AC surge protectors? I am designing a standalone piece of equipment that has some solar panels charging a battery bank, and then some equipment being powered off these batteries. I want to know if I should put DC surge...

Hey, I am trying to work out the cascading on an old Merlin Gerin CM1600 circuit breaker. Basically, the product is so old that there are no cascade tables so I can't find out if the downstream breakers can withstand the fault current. Does anybody know how to calculate this? I normally just...

Hey guys, sorry for being ambiguous (funny how it makes sense to yourself but then you explain it to other people and it doesn't come out clear!) 1) The network provider doesn't allow backfeed of any more than 5kW in this area. The site is grid connected. 2) This is for a very small factory...

Hey guys, Does anyone know about an inverter for a solar system that will supply power to an installation, but if more power is required it gets it from the grid? I am an electrical engineer, but I haven't had a lot to do with solar. Typically what I have seen is things like houses with solar...

Step 1: In the PLC, if the variable changes to the defined value turn on a bit/flag Step 2: When flag is set turn off the bits of code you don't want to run In some PLC's you can deactivate whole programs at a time by setting a bit. Sometimes you can change the PLC state by setting a controller...

Sorry about the late reply to this thread - it took me a while to get the information I was after. The desired evaporator temperature is -17 degrees Celsius. The refrigerant is R404A. While I was snooping around the machine I found an existing pressure switch that may have the answers I am...

Hi, I have been asked to control some refrigeration compressors with VFDs to save power. I've done a lot with VFDs over the years, but this has never come up yet. I've done a fair bit of research and am pretty confident I have everything figured out - I was going to control the compressor...

My father was a motor rewinder, and working with him I have had quite a bit to do with both types. You will find aluminium motors are generally only in smaller frame sizes. I haven't seen one much larger than 3kW. They are usually a bit cheaper and easier to install (because they are lighter)...

Thanks, I will have a look into that. You never know sometimes. After looking more closely I suspect it may be related to a bad installation. Because they had to fit this to an existing board, they have used a huge CT to fit around the busbars, and one of the phases is much closer to the...

Hi, I have an old resistive starter that has been overhauled. We installed 8 new 250A contactors, all with 240VAC coils. When we were testing the starter the main RCD to the board would trip when the third contactor turned on. It should be noted that we did not have the motor connected at this...

Not really a PLC question, but there are no forum categories for SCADA and I know most of you guys will (like myself) do a lot with SCADA... I need to talk to an Enercon wind turbine. The correct way to do this is via an OPC server that communicates using the IEC 61850 standard for talking to...

Hey all, Thanks for the many comments. I think we have identified the source of the problem. Well, maybe the source of the problem, maybe a symptom. When we took a close look at the busbars we could see that there was tracking near the standoffs. The tracking was unusual though - the burn marks...

Hey, Thanks for the comments. I will check out the harmonics on the plant, but I would bet my first born child that it is almost zero. The entire plant only consists of electric motors, and they only have star/delta and autotransformer starters. The plant was fully running at the time the board...

Hi all, I have a bit of an unusual one here, and I was wondering if anybody has come across something like it (or maybe a PFC expert could point me in the right direction). I recently took a look at a power factor correction unit that had pretty much totally blown up. All of the capacitors have...