Typical limit on equipment is 5 uAmps, but you can actually fail testing on a unit that has greater leakage current inherent to design. 1)Limit (usually on the order of kilomegohms) to design or build for depends on the UL, ANSI, or Military spec that is usually called out by a customer. 2)Measured value with DC Megohmeter to look for depends on size of the part, and resistivity of the insulation materials. Resistance between isolated windings will be defined as (area of interface) divided by (thickness of insulators) x resistivity of insulator. Resistivity is normally a listed mfgr value.
Engineers that I have worked with state in their specifications that all meggered wires must have a reading of 5 Meg ohms or higher. If the reading is lower that this benchmark start checking splices especially if it is an underground installation. Water usually accumulates in underground conduit systems and when the wires are pulled in there is a certain amount of conductor scraping. This starts the downward spiral from infinity. Check termination points close to the exit point of the conduit. A certain amount of evaporation from the conduit condensates on the terminal points.
A 228 sq mm conductor equates to 450 MCM. A conductor of 450 MCM is not a standard AWG wire size. A standard 400 MCM will carry 380 amps. A standard 500 MCM will carry 430 amps. Difference between 400 and 500 MCM amperage's is 50 amps. Transposing between the two amperage's of 50 amps will be 380 + 25 = 405 or 430 - 25 = 405 amps. This is a very rough calculated answer for the question.
Wire sizing is based on the load that the conductors carry. The breaker is then sized to protect the wire. To get to an amperage the wires are going to have to be paralleled. The calculations are already sized in the electrical code books, CEC and NEC. These are code books used by North America electricians. A 500 MCM conductor with an insulation factor of 90 degrees C is rated at 430 amps. Four 500 MCM conductors paralleled will give you an ampacity of 1720 amps. The breaker will need to have a 500 MCM 4 barrel lug to receive the conductors. The same thing with the load end, it will also need a four barrel 500 MCM lug.
It depends on a lot of factors. Generally speaking, if the insulation is THHN then the rating is 350 amps. If the insulation is THWN then the rating is 310 amps. The ampere rating for wire depends on the temperature of the environment it will be used in, the insulation rating and the number of circuits installed in a conduit. There are also other factors to consider... like voltage drop in long runs.
There is no defined AWG for 350 MCM. The American Wire Gauge stops at 0000 (4/0), and 350 MCM is bigger than this. An approximate conversion would be 6/0, if there were such a thing. Extrapolating out from 4/0, 6/0 is 334.8 MCM, and 7/0 is 422.2 MCM. These wire sizes don't exist of course, and don't exactly match 350 MCM anyway.
Engineers that I have worked with state in their specifications that all meggered wires must have a reading of 5 Meg ohms or higher. If the reading is lower that this benchmark start checking splices especially if it is an underground installation. Water usually accumulates in underground conduit systems and when the wires are pulled in there is a certain amount of conductor scraping. This starts the downward spiral from infinity. Check termination points close to the exit point of the conduit. A certain amount of evaporation from the conduit condensates on the terminal points.
500 mcm
The amp rating of a 500 MCM (thousand circular mil) cable can vary depending on the insulation type and installation conditions. Generally, a rough estimate for a 500 MCM cable with THHN insulation in a typical installation would be around 380-400 amps. However, it is recommended to consult the manufacturer's specifications or a qualified electrician to determine the exact ampacity for a specific application.
The required size of a conduit raceway for a 3-5000 mcm wire is 300 kcmil. It maximizes the limits on the wire fill for raceways.
m = 1000 c = 100 d = 500 MCMD doesn't make sense MCM = 1900 MD = 1500 CM = 900 so it would be MCM + D = 1900 + 500 = 2400, but that would be written MMCD
2.2 lbs per ft
A 750 MCM copper conductor with an insulation factor of 90 degrees C is rated at 500 amps.
A 228 sq mm conductor equates to 450 MCM. A conductor of 450 MCM is not a standard AWG wire size. A standard 400 MCM will carry 380 amps. A standard 500 MCM will carry 430 amps. Difference between 400 and 500 MCM amperage's is 50 amps. Transposing between the two amperage's of 50 amps will be 380 + 25 = 405 or 430 - 25 = 405 amps. This is a very rough calculated answer for the question.
mcm
what is mcm corce
For a 400 Amp service with 500 MCM conductors, the minimum size grounding electrode conductor required would be 3/0 AWG copper or 250 kcmil aluminum based on the NEC Table 250.66.
This is a voltage drop question. A 500 MCM copper or 750 MCM aluminium conductor will limit the voltage drop to 3% or less when supplying 300 amps for 500 feet on a 240 volt system. Paralleling these conductors will allow the rating to be increased to 600 amps.