There is a possibility the motor manufacturer used less insulation on the neutral end windings, which may result in premature failure if operated continuously in this manner. It may also be less resistant to surges (lighting, capacitor switching, etc.). It is advised to confirm with the...
I don't know why you guys are so strong on the UPS recommendation. They require battery replacement or complete replacement every few years. In an industrial environment where preventive maintenance is always "tested", the UPS will likely run to failure resulting in more contactor chatter when...
If you can't easily get an independent 120V source, a constant voltage transformer (ferroresonant; such as from SOLA) will work well for this application. They are big and lossy, but reliable and maintenance free.
I have searched a long time for a hermetically sealed relay capable of 5-10A DC break ratings at 135VDC for use in hazardous locations. I recently found some hydrogen filled DC contactors from Tyco and Gigavac with astronomical current and voltage ratings for their small size. We plan to...
It is difficult to quantify the advantages of copper over aluminum. I have seen many aluminum rotor cage failures attibuted to periodic start/stops. Aluminum fatigues faster than copper, and also expands more than copper due to temperature fluctuations.
I have seen copper rotor cages fail due...
How about Electro-switch? They build 12 pole switches up to 400A (600VAC), and 6 pole up to 800A (600VAC).
http://www.electroswitch.com/electroswitchesandrelays/default.htm#
What type of cables are you presently experiencing failures with? Cross linked polyethylene notorious for water ingress? Are these shielded cables?
There should not be any issues using cable rated for underground conduit or direct bury service if it was not mechanically damaged during...
Thanks for the information. The leads were correct, but I would like to purchase a 3 channel scope for future verification. Any recommendations? I found a 4 channel handheld unit, but am not familiar with the manufacturer. Also, how much/fast does the rotor need to turn? On motors this...
What would be the consequence of inadvertently rolling lead 1 and 4 for example on a 6 lead, wye connected induction motor assuming 1, 2, 3 were the phase leads and 4, 5, 6 were the neutral point.
The new configuration would be 4, 2, 3 phase leads and 1, 5, 6 neutral. This is probably a simple...
What specifically are you tasked with?
In my experience in a similar facility, running at reduced rates always resulted in reduced efficiency. The reason is the plant is designed for peak efficiency at peak load. The base plant operations must still be run, regardless of actual output. If...
I have seen this type of connection fail after just a few years, but it was an outdoor application exposed to cooling tower drift. The AL had corroded, and pitted away where the CU was in contact. Additionally, the AL oxides swelled in between the connection, forcing the lug away from the pad...
In the USA, what are the regulatory standards to reference when applying hazardous location requirements to automotive vehicles, for example?
NFPA 505 is as close as I can find, but this applies only to special purpose industrial trucks and specifically not automotive vehicles.
Intuitively...
MIL-HDBK-217F
Is this a protective or control relay? 217F covers control relays. The IEEE Gold Book may also be useful.
http://www.sre.org/pubs/Mil-Hdbk-217F(2).pdf
My technology issue is that it facilitates escalating resource consumption by allowing the population to rise above natural equilibrium. The further over the balance point it gets, the greater the consequence for any small inturruption in services.
I'm not anti-technology, but I am against...
josephv,
You are basically missing the point of many posts above. The only thing technology does is increase the rate at which humans consume energy; either through increased mortality, increased population, increased productivity, or increased leisure activities. Simply saying technology is...
A few posts up, you state that instantaneous is set for 3kA @ 0.1s. Is this how you justify not using fuses? If so, this presumption is incorrect. Power circuit breakers aren't even fast enough to clamp current - contactors are much slower.
You state that available fault current is 17kA and that max contactor interrupting current is 4.8kA, but that you don't need fuses? I disagree. The only medium voltage motor starters that don't have fuses are circuit breakers in NEMA world. All contactors have fuses or some other short...
