I would recommend the GE guide to short circuit calculations. If you google this you should find the link below which has a very helpful document on calculating short circuit.
http://www.geindustrial.com/publibrary/checkout/GET-3550F?TNR=White%20Papers|GET-3550F|generic
The basic things you...
I also agree with David. 3/C +G is a cable that consist of three inculated conductors and a ground in an overall jacketed assembly. 3-1/C +G are three seperate insulated condcutors with a ground. The 3/C cable assembly is tightly constructed so it typically would have a lower AC impedance...
A UPS could be a good solution. However, be warned that you will need to size the UPS to handle the startup current of the motor. Generally UPS units don't handle motor loads very well unless they are overized to compensate for them. Many UPS units have a dynamic bypass that will momentary...
I had a similiar application with a 150 HP two speed fan used on a cooling tower. We took the two speed starter out and replace it with a VFD. We perminentely shorted the apporpriate wires together for the high speed configuration (need to be carful with overload setting coming off the VFD 3...
Another alternative that would probably be more expensive but would likely solve all your power issues is to invest in a UPS (uninterruptible power supply). Many manufacturer's offer solutions in the 30 to 50 kVA range. I would install a surge arrestor on the input to the UPS. I have used the...
MKFPE,
Thanks for the feed back. The material that some of the vendors are proposing is a fabric that passes water but blocks oil. They are proposing a fabric to block the water on the bottom and on the sides to provide a combination of fabric that blocks water with panels that would have...
I am looking for an inexspensive way to provide oil containment around existing transformers. Does anyone have experience using these specialy fabric materials that allow water to pass through but stop oil.
ch2mguy,
I'm glad you were able to solve your problem. I have struggled before with tripping issues on motors. Here are some thoughts for future use
1. If the motor is tripping instantly on start then it could be an inrush issue. Especially if the NEMA code letter on your motor is an "H"...
The current electrical code does not allow the equipment ground wire on a recepticle to be connected to the nearest water pipe (unless the connection is made within 5 feet of where the water pipe enters the building - see NEC code section 250.68C1). This could be a real hazard if the water pipe...
yes I agree with waross. The voltage between two phases will be 480 volts. the diagram that you have looks like an autotransformer connection. I have used autotransformers to increase the voltage form 208 volts to 220 volts to run equipment that has a 220 volt rating and is too sensitive to...
mgtrp and stevenal: I reviewed the zero sequence connections for a wye-wye transformer and I agree that without the primary side grounded there will be no zero sequence current on the secondary. Thanks for clarifying that for me. I have not worked much with wye-wye configurations. On the...
For mgtrp: I would think if the secondary side is solidly grounded (600/347 side) then during a ground on one phase on the secondary you will have a large groud fault current flowing on this phase to ground. The voltage on the other two phases with respect to the neutral point would stay...
Does anyone have any suggestions or experience with moth balling two 12 MVA oil filled transformer? We would like to leave them denergized for a year or so and only renergized in an emergency situation. Not sure if its simply a mater of turning off and placing a slight nitrogen purge on top...
Of course it would be the best to have the whole package listed but I see your point that these are custom systems. If the system is not listed as a package then the local inspector will need to examine the whole skid to ensure the proper seals and wiring methods, etc. have been used to assemble...
As indicated by others you need to think about how the E-stop is wired to the input of the PLC. The PLC processor will scan or read all its inputs and then look at the ladder logic in the PLC. If the input has voltage on it then the PLC when it scans it places a logic 1 in its internal memory...
I would think that the original configuration delta to wye blocks the zero sequence current. If you go with the wye wye configuration I would think that a ground fault on the LV side could be fed from the HV side and vise versa. In addition you may want to consider the affect of a voltage sag...
I vaguely remember a similiar problem with a SLC5/04. I had one that was running a program but like you whenever I tried to down load the program I received the corrupted message yet I knew the processor was running properly. I remeber that it was finally resolved by contacting my local...
There are some good ideas people have suggested. One thing I would encourage you to do is to set up some monitoring of the power at various points in your system. You will need to have meters that can capture power quality information such as voltage sags and surges, harmonic containt of the...
