We are trying to determine lighting requirement for a small process building. Is there a quick way to help determine wattage requirement per square footage? What about celling height? Thanks!
We have a situation where we have to route MV (4160v) cable in a LV duct Bank. Routing will involve Man Holes where LV and MV will be exiting PVC conduits and entering others as they head to their destination. MV cables are all shielded, with shields grounded on both sides. My question is, when...
I'm planning to add motor loads to an MCC fed from a 4160v swicthgear. For that, I'd like to to run a load flow and short circuit analysis to see if existing system can handle it. Both existing swicthgear and MCC have existing motor loads on them. My question is, if the plant gives me short...
I'm configuring a 4 wire 120/208v panel and have this question. I have a 1581VA load, that I'd like to supply with a 2-pole 208v supply (Vac). I understand that a current of 7.6A would be seen by phases A and C. What does that mean VA wise to each phase? In other words, would each phase's load...
Electrical system study with all loads connected showed we need to modify primary Taps to -5% to maintain voltage. Currently, most of the loads are not connected, and bus voltages at MV level is around 4300v. If Taps are changed now, voltages might get over 4500v, which is high. First, would a...
I'm feeding a 1200A MV breaker directly from the secondary side of a 69K/4.16K transformer. I'm using 6 1/C #500 MCM (2 conductors per phase). Table 250.122 in NEC-2011 indicates a ground size of 3/0 if overcurrent device protecting cables is 1200A. In this case, there is no overcurrent device...
I have a feeder with CO-9 relay I'd like to coordinate with downstream breakers. The time delay element is adjustable, but the instantaneous element (IIT) is the problem. Does anyone know if we can add a timer to the IIT element? How is that done?
I have a switchgear cubical with a ground bus. The case is all grounded through the ground bar. The bar is connected to a local ground, and the 4160v feeder ground. We have multiple power circuits terminating in the switchgear, 120VAC, and 125DC. Do I have to pull a ground cable and terminate it...
I have a 1187W motor space heater rated at 120V. I'm using 12AWG wire. The cable length is 450ft. I found a table indicating resistance for this size cable is 1.588 for 1000 ft, which means 0.7146 ohms for the 450ft. How is voltage drop calculated in this case, knowing that current will not be...
We are feeding a main breaker in a MV switchgear line-up by a secondary side of a transformer. We want to use the same feed to feed an other breaker. In doing that, we would be running a cable from source side of main breaker, to the new breaker, instead of feeding the new breaker directly from...
We have an old medium voltage Allis-Chalmers switchgear system. The breakers are rated for 1200A, and 29KA interrupting rating. The e-tap model shows a 3-phase bus fault value of 40KA. This is all contribution at the bus these breakers are connected to. My question is, when we are considering...
I have a 4160v MCC being fed by a feeder breaker in an other building. The feeder cable is 3 1/C #1000MCM, and is being run underground. The MCC equipment is locally grounded to a local ground in the building. But in addition to this, we have a grounding 4/0 5kv cable running with the 3 1/C...
We have a 4 pole inverter duty motor with a 5:1 speed range and 700 Powerflex VFD. The vendor claims a 29.27 to 1 ratio gear box, will allow us to run the Drum at .24 RPM @ 12 Hz, and 1.2 RPM @ 60 Hz, and running @ 75 Hz would allow us to run at 1.5 RPM with no drop in torque. I'm not sure how...
I have a situation where an other feed needs to be added to a 28 MVA delta-to-Y transformer. The Transformer currently has 2 feeds, with 2 CTs paralleled for differential protection through HU differential relay. each CT is 4000:5A and connected in delta. I need to add a third feed. Do I have to...
Hi there. I have a question regarding bus rating. Does higher actual bus voltage mean current rating should be lowered? For example, if a 4160v bus is rated at 2000A, would that rating decrease if the XFMR feeding the bus is at a higher tap? In other words, should I worry about Amps or MVAs?
