Thank you Waross and Che...
My confusion is clear...that additional √3 factor not to be applied for calculating voltage drop, as current is calculated considering 58% of nameplate rating.
Other than that I agree that conductor needs to be derated based on grouping of cables, however, conductor...
Che,
My question is we are measuring voltage line to line, so, considering 3Phase system, factor of √3 should be applicable.
so, when calculating voltage drop formula should be √3x58%xIxR.
This is where I am confused.
Thanks for detailed response Che !
However, I am still having doubt.
1) The cable from MCC to motor and from Motor back to MCC, both are in series with motor winding before formation of delta in MCC.
Considering this, why voltage drop should get half? Instead 58% current of nameplate delta...
Thanks Waross
Yes, I have considered 58% current of nameplate current for cable sizing.
However, I am confused about voltage drop formula in delta...as delta is formed inside MCC.
Whereas, voltage drop is being measured inside delta winding.
Hi,
I am trying to size cables from Star Delta Starter to Motor
During Star connection,
Load Current in Cable from SWGR – Motor Term. U1, V1, W1 = 1/3 (33%) of actual FLC
Load Current in Cable from SWGR – Motor Term. U2, V2, W2 = 1/3 (33%) of actual FLC
Starting Current in Cable from SWGR –...
Hi,
We are experiencing peculiar problem at site, which is causing our process plant to trip.
Our plant has 2.3kV MCC where motor feeders uses the GE Limitamp Contactor (CR193V), which were retrofitted with Vacuum bottle in past. During retrofitting, Contactor Economizing Module (CEM) were...
7anoter4,
NEC ampacity as per Table 310.16 for XHHW-2 (90oC) conductor, ampacity is 260Amp @30oC, whereas IEC ampacity of 235Amp is comparable only if one no. rack with 9no. multicore cables.
However, in case of multiple nos. of racks, derating factor further worsens.
Example, for 6 Nos. racks...
7anoter4,
Thank you for your explanation. However, I would like to correct some figures in above.
As per NEC Table 310.16, for XHHW-2 (90oC) conductor, ampacity is 260Amp @30oC. Are your referring to 90oC or 75oC ampacity ? I understand that 75oC ampacity needs to be used only for checking...
7anoter4,
Yes, you are right, I should have said XHHW-2 cable.
But, do you mean to say if TC type cable is used and cables are kept touching to each other, there is no need to derate the cable ampacity ?
Waross,
In case of multiple conductors in raceway, derating is applied as per below NEC...
Hi Guys,
I have following query regarding NEC code requirements for cable ampacity derating.
We have following situation for calculation of motor cable sizes for cables leaving from one of the MCC in Substation.
Cable Laying Condition: Uncovered Cable Tray
Nos. of Power Cables in tray...
