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ELECTRICAL PROPERTIES
1. Material: 6063-T6
2. Resistance (μΩ/ft): 16
3. Resistance across Splice (μΩ): 11
4. Resistance of 24ft length With Splice (μΩ): 197
5. Copper Equivalent (MCM): 1250
6. Continuous Current Rating (50°C Rise) (amp): 1260
7. One-Second Rating (50°C Rise) (amp): 68,500
8. Conductivity: 53%
9. Electrical Resistance @ 20°C (μΩ/in²/ft): 15.37
10. Electrical Resistance @ 20°C (Ω/CM/ft): 19.57
SYSTEM BALANCE
Superior Bus is a power distribution system using single conductor insulated power cables and support blocks to maintain power cable spacing. Each phase consists of one or more cables connected in parallel. The assembly is enclosed in a ventilated aluminum or steel enclosure for support, protection and is designed for intra-phase balance. Most phasing arrangements provide inter-phase balance of currents due to the load impedance, but only a few of these combinations provide a minimal intra-phase current unbalance. Superior Bus is a fully engineered system utilizing phase arrangements which reduce the amount of parallel conductor unbalance to a minimum.
SHORT CIRCUIT CAPACITY
A Superior Bus system must be able to withstand the forces created by short circuit currents. Under short circuit conditions, these forces are transmitted from power cables to the cable supports. The support blocks and enclosures in our Superior Bus are designed to withstand the mechanical forces that are transmitted from the power cables to these power cable support elements.
The major concern regarding short circuits is the dangerous mechanical forces that can result. However, it is still an electrical problem in determining its magnitude and prevention. Short circuit currents are made up of a symmetrical AC component and a rapidly decreasing DC component. The high voltage breaker interrupts the symmetrical current to protect the electrical system.
A Superior Bus system has the mechanical strength to withstand the maximum short circuit forces developed in any given application. Since Superior Bus is typically used as main feeders from a generating unit or power substation to load centers, switchgears and high voltage machineries, the available short circuit of the system will be that of the generator supply through the transformers. In an electrical installation where the Superior Bus is a feeder of a large motor, the available short circuit current contribution of the motor has to be considered.
For most applications and design considerations, a three-phase short circuit current will result in the maximum mechanical forces. The short circuit current data is available directly from the utility companies if the cable bus is feed directly to the utility company service, However, when the cable bus is connected to the secondary of a transformer, the formula below is used to calculate the three-phase fault current:.
I = (KVA x 1000 x 100)/ (1.73 x E x z)
I = RMS Symmetrical Fault Current
KVA = Transformer Rating
E = Secondary Voltage of Transformers
z = Impedance of transformer in Percent
Where motor contributions are considered the fault current due to the motor feedback will be a function of the voltage and is usually expressed as multiples of the motor full load current. NEMA standards are available which list these factors.
PARALLEL CONDUCTORS
Parallel conductors (more than one per phase) can be used to an advantage in a Superior Bus system where large conductor sizes are encountered, the capacity per circular mil of conductor decreases as the circular mil of conductor increases. Smaller conductors running parallel are more flexible during installation and have greater current carrying capability than fewer, larger conductors
VOLTAGE DROP
In the design of an electrical system, the voltage drop in the power feeders as well as the entire power system should be considered. Voltage drops of 3 to 4% for power feeders and 5% or less for the entire power system are within the acceptable limits. Superior Bus is designed to attain a low-voltage drop.
AMPACITY COMPARISONS
Based on the NEC & ICEA Tables at 90°C in 40°C Ambient, the following table illustrates the greater current carrying capacity of Superior Bus as compared to other methods:
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