Does anyone now if there is any Standard, that required equipment grounding connection testing (resistance measurement) from equipment to the ground grid? Or a visual inspection is enough? I dont find any requirements in NFPa70. Not sure if resistance measurement from equipment (motor...
In NEMA 01 is specified that "For machines rated 601 V and higher, accessory leads shall terminate in a terminal box or boxes separate from the machine terminal housing. What about lower than 600V? Is a terminal box required by NEMA for space heater leads? Is there a table with space heater size...
Hope I understand the question.
1. I will not consider the conduit as a ground for the panel. The new panel has to have it own ground in my opinion. However article 344.60 says RMC shall be permitted as an equipment grounding conductor.
2. Each conduit has to be grounded. From this point of...
I start commissioning test for some switchgear 2 years ago. I did not finish commissioning, and due to company low budget, I had to stop this work for 2 years. Are those test that have been performed still valid? Or those test should be repeated again? Is any Standard that describe this? I will...
As you all understood, I am interested in finding the best method on the market to evaluate expected life expectancy of cables. As I red into some papers on the internet, and also in a EPRI report, usualy they recommend tan delta that will give a average information about insulation (can't made...
What testing method for MV cable insulation do you thing is more reliable? A tan delta that gives a general quality of insulation for entire cable plus a pd test? Or tan delta plus VLF hipot test? I am looking to find the best way to do cable insulation testing, and I need a method that can tell...
Usualy the no load current can get to 30% of nominal current. So 90A seams a little high; First step is to check the bearing health. One cause that can get to a higher current is if you just put vaseline to you bearings; in this case at the beginning the current will be a little high but if you...
Isolation class - F. According to manufacturer, this motor can work to a temperature of 100C. The air flux is cooling down only external frame. Protection- IP55 according to IEC Publication 34-5 (but I don't think that counts). Also according to manufacturer, this motors can work with 108% from...
A motor of 45 kW from a ventilation unit, (nominal current 82A) due to a bigger load, function actually at 95A-measured current. The motor is cool down by a big air volume of 15C degrease. What are the odds that this motor to be burn? All the cold air can compensate the overcurrent effect? I...
13.5A each. The instalation is design to work with one pump in stand-by and only one pump running and we usualy do this way, but 2 weeks ago, bouth pumps where on, and I observe this diference between currents. Probably the current is bigger when bouth pumps are running due to a bigger pressure...
In one instalation of two identical centrifugal pumps that feed the same collector, I observe that if bouth pumps are running the current is around 13.5A, but if only one is running and the other one is in stand-by, the current is 11.8A. The nominal current of motor is 12.5A. Can someone explain...
Supose I test a thermal relay (bimetalic) using current injection-2*setting current(Is) and the tripping time is not correct. Let say is bigger. What will be the write action?
1. Adjust the setting current of thermal relay at a smaller value-Iss and inject again 2*setting current(Is). The...
First of all, you shoud install a current recorder (if you have one) on all three phase, and let it there until the breaker trip. You will find out the exactly current values (maybe there is a peak value, cause by a load starting, transformer, or motor, or something else) and you will be with...
Is there any prescription that say from what voltage or current thermographic scan is relevant? If not, from yours experience can you give some values?
Thank you!
