As an update...
Contacted the manufacturer of the transformer that we received the quote from. They are fine with applying a lower kva nameplate value so we can meet the cutoff for the smaller cable. In theory- the unit is still the same, but the impedance pu value will change slightly as the...
In Canadian Electrical Code- does 8-104(4)(b) [8-104(d) reads: With 100% rated circuit breaker, 85% of the rating of the circuit where the ampacity of the conductors is based on Column 2, 3, or 4 of Table 1 or 3] still apply if we're sizing DLO cable based on Table 12E [Allowable ampacities for...
Waross, I agree. This is being fed from a 15kV breaker with a relay. Given code, minimum size conductor ampacity is 261A. Max CB setting is 627A. There'll be some coordination with breaker setting to allow for inrush, however its likely that the CB will need to be set greater than 125% FLA...
Is it common that a transformer could be rerated with a new nameplate to a slightly smaller kVA in order to maintain code requirements for cable sizing?
For instance, a 5MVA transformer primary is a few amps more than the ampacity of a smaller cable. To bump up a size would be a ~$20k cost to...
I do see this....
14-414 Connection to different circuits
(1) Where electrical equipment is supplied by two or more different transformers or other different sources of
voltage, then
(a) a single disconnecting means that will effectively isolate all ungrounded conductors supplying the
equipment...
Is it allowed to use a multi-conductor cable using 2 wires for Circuit A: 208V exhaust fan originating from a contactor in a panel, and also use 2 more wires of the same cable for a 120V line voltage thermostat that goes back to the same contactor control circuit? The thermostat switches the...
Duly noted Waross- I left that point out just to compare apples here.
And yes jraef, I understand you set the overload to the amperage of the motor, while it incorporates the 125%.
I suppose where Eng 2 is trying to make a point is perhaps with rule 14-104 and Table 13. 1c is not explicitly...
Canadian application here, but should not be different than NEC. I'm in the middle of a tussle between two very experienced guys here about conductor sizing on a motor branch circuit fed from a MCP and OL.
Example:
On a 50HP/600V motor- FLA=52A as per code table.
Simple Calcs:
52A*1.25=65A...
Hi Guys,
Looking at specing some switchgear bound for Australia. We have zero specs other than they want a Terasaki breaker. I know this is a fairly open-ended question, but I am looking for direction on possible certification requirements for Australia-bound low voltage switchgear.
Am I...
Artisi- not a diesel, its a nat gas. Likely 1500 because it was built/designed in europe meant for 50Hz system.
iop95- No. Engine is designed and built for most efficient operation at 1500rpm. Yes theres some drivetrain losses but such is life.
Ah interesting.
Our engine is 1500rpm gearbox to a gen spinning 1800rpm.
I received some info about the gearbox and coupling inertia values which is good. Would it be correct in thinking then:
Drivetrain is the following:
engine-coupling-gearbox-coupling-generator
where w is inertia...
We're driving a gen through a gearbox. I have the value of the engine moment and the generator moment. How would I calculate the combined value of moment of inertia for the genset?
Say we have two groups of 2 generators, each group capable of 4000A output. And we connected the load/utility line to the middle of the bus between each group. Can we get away with sizing each generator switchgear bus to 4000A each, and simply have a middle transition cell with 8000A of bussing...
Looking at ratings on some motor protection circuit breakers, they have ratings for say, 277Y/480 or 347Y/600. If we have a low voltage generator with resistance grounded neutral, it's not considered a delta system really, but we also wouldn't consider it a 277Y/480 correct? So in effect, these...
We have a 1500A utility feeder with 1500:5A protection CTs. We are connecting internal generation that will displace the utility power, but not export power to the utility. We will maintain a minimum import, and when we do, we can have as little as 20A incoming from the utility.
For the purpose...
Thanks mls1, that clarifies some things there. Guess I was really wondering if there's any way to detect a ground fault on a solidly grounded system with my present setup.
We have a 4160V to 600V Delta (primary) Wye (secondary) transformer, 1.5MVA.
I had planned to simply ground the neutral on the secondary wye side as the load bank does not require line-neutral load. I understand that this poses a risk for excessive ground fault current to flow.
We have a zero...
I have a 1.5MVA transformer with a 600V secondary. The transformer is a 220 class transformer so 40degC Ambient + 150degC Winding Rise + 30degC Hot Spot = 220degC.
My question is: What temperature ratings do the cables have to be?
If you were to analogously compare a transformer insulation to...
Before anyone says- I've already completed a search on here for info about sheath grounding. Regardless, I still have questions.
Situation: Parallel 480V generators placed 25ft away from switchgear. Some applications have ~400A/phase, some applications have 1800A or 900A/phase in parallel runs...
