Hi,
For cable insulation resistance calculation, the equation goes:
IR = K * log (D/d) [megaOhm-1000ft]
where D = diameter of insulated conductor
and d = diameter of copper inductor
ICEA has some K numbers for PVC and rubber. But how is K calculated? It's nowhere explained. I've come...
Hi,
I have a cooler powered by a small motor. The cooler motor is adjustable 0-60V (the higher voltage, the colder the cooler gets). Since a soft start is preferred, I use a typical Variac to slowly turn the voltage up in the lab.
However, I'd like to set up a simple input/output system...
Hi,
This is kind of a "spin-off" thread from the other one that I posted before.
http://www.eng-tips.com/viewthread.cfm?qid=188842&page=3
I have a 2kW Sterling cooler load that needs a backup system, and the performance drops off sharply outside 60Hz +/- 0.5Hz.
Besides UPS, "Itsmoked"...
For a diesel backup generator, what's the typical output frequency variation? I've read specs that say 60Hz +/- 5%. Is it typcially off by that much?
In my application, the load is very sensitive to frequency variation. The performance starts dropping when it's outside of 60Hz +/- 0.5Hz...
I'm looking for a cheap current limiting device that will cap the current at 25mA from the 120V wall plug. I read that a PTC thermistor would do what I'm looking for.
Has anyone dealt with thermistors? I guess I just need to look for one that allows normal operating current at 25mA, and...
Hi,
What kind of device should I look for if I want to control the voltage source feeding a gauge based on temperature readings?
What I'm trying to do is to ensure the internal temp of the gauge doesn't get too hot. So I want to have some kind of temp sensor to read the internal gauge temp...
I was just told by someone that you can send both AC and DC voltages down the same cable at the same time (to a Wye motor winding). There's a sensor gauge that requires DC voltage and has a lead connected to the Wye neutral. The guy's reasoning is that the motor only sees the AC components...
Could someone explain what a choke does? I read from one site that it converts AC to DC and another that it filters AC frequency. I thought AC to DC was done through a rectifier. I'm a bit confused.
Hi,
I know that higher dielectric constant (relative permittivity) yields higher capacitance. So I always assumed that the higher dielectric constant, the better insulation material it is...therefore, higher voltage breakdown.
But I just came across some references showing that voltage...
Hi,
I'm working on a long term testing (26 weeks) on cable insulation. The readings that I've taken are capacitance, AC/DC resistance, and dissipation factor at constant 75 deg C.
As expected, the AC insulation resistance for different samples has either stayed the same or dropped after 26...
Hi,
Could anyone tell me where I can look up standards for subsea cables regarding whether a ground wire is required? If so, can we rid of the ground wire by conduiting the cable?
Thanks.
Hi,
I'm not in power engineering and am having a little trouble putting the fundamentals in the big picture.
1. How does a power cable's insulation (rubber) thickness affect the capacitance and inductance of the cable?
ex: if insulation thickness goes up, L goes up and C goes down?
2...
I'm considering going to grad school in Mechanical Engineering. But I realized that some schools offer Master of Engineering besides Master of Science. What's the difference? Does M.Eng have less prestige than the other? I've never seen any job posts looking for Master of Eng., it's always...
This is a stupid question, but how are cable ratings established? Is it based on the thickness of insulation or cable gauge size?
Does a 4kV rated cable mean 4kV peak voltage? So can it actually take on 8kV of peak to peak voltage?
thanks
if we spliced AWG#1 and AWG#2 in one cable reel, what is the acceptance criteria for the current leakage since both AWG size have different acceptance criteria? which of the criteria would apply? AWG#1 or AWG#2? and also the same thing goes for resistance test, what is the criterion for that...
I'm going to be doing a hipot breakdown on some wires with rubber insulation in an oven chamber. The chamber has a hole on top and bottom where I can connect the AC output and ground. The oven is going to be set at 550F while breaking down. If I wrap a portion of the insulated wire with metal...
Hello,
I was looking up max. current for different copper AWG sizes, and I found different amperages every time. Why is that? Is there any standard for this case? Would appreciate any advice.
Thanks
Does any one know what is the IEEE standard for partial discharge testing on power cables?
And is there any other way to look up IEEE standards without subscribing to the IEEE website?
Thanks
Hello,
I encountered a voltage increase during the DC hi-pot test for our ESP (electrical submersible pump) power cable. Normally when doing a DC test at 10kV for 1 min, it'd stay there and pass the test...or drop back down to fail. However, in this instance, when testing this 4kV rated...
How do you calculate zero sequence resistance and reactance for an Electrical Submersible Pump (ESP) power cable?
As someone indicated, to calculate for zero sequence resistance, I'd have to include the resistance of one of the phases, plus three times the resistance of the cable outer shield...
