You're welcome! That's a great question. Here's why companies generally don't run electrical phases in separate conduits (called "phase-separated" installations) and why it's strongly discouraged by electrical codes and best practices

1. Inductive Heating and Power Loss (Major Reason):
Magnetic Fields

When current flows through a conductor, it creates a magnetic field around it. When all conductors of a single phase are run together, their magnetic fields tend to cancel each other out. However, if you separate the phases into different conduits, the magnetic field around each phase conductor is much stronger.

Inductive Heating of Conduit

This strong magnetic field induces circulating currents (eddy currents) in the metallic conduit itself. These eddy currents cause the conduit to heat up significantly. The heat can become so intense that it can damage the insulation of the conductors within, creating a fire hazard.

Increased Impedance & Voltage Drop

The inductive reactance increases dramatically with phase separation. This increases the overall impedance of the circuit, leading to:

Higher voltage drop

The voltage at the load will be lower than the voltage at the source. This can cause equipment to malfunction.

Increased power loss

More energy is dissipated as heat due to the increased impedance. This reduces efficiency and wastes money.

2. Safety Concerns



Conduit Becomes Energized

The induced currents in the conduit can make the conduit itself electrically "hot" or energized. Touching the conduit could result in an electrical shock, even if the conductors inside are properly insulated.

Arc Flash Hazard

A fault condition (like a short circuit) is likely to be more violent in a phase-separated system due to the increased inductance and the energy stored in the magnetic fields. This creates a greater arc flash hazard for anyone working near the equipment.

3. Code Violations (NEC and other electrical codes)



NEC 300.3(B) Conductors of the Same Circuit

The National Electrical Code (NEC) in the United States, which is widely adopted, specifically requires that all circuit conductors, including the neutral (if present), be run in the same raceway, cable, or enclosure. This rule is intended to minimize inductive reactance and prevent overheating. Similar requirements exist in other electrical codes worldwide.

Similar rules exist in Canada (CEC) and other national electrical codes.4. Practical Installation Issues



Synchronization

It's essential to ensure that the current and voltage are synchronized correctly in each phase. With phase separation, this becomes more difficult to manage and verify.

Complexity

Separate conduits for each phase significantly increase the complexity and cost of the installation. You'd need more conduits, more fittings, and more labor to install them.

5. Reduced System Performance



Harmonics

Phase separation can worsen harmonic distortion in the electrical system. Harmonics can cause overheating of equipment, misoperation of electronic devices, and increased energy losses.

Power Factor

The increased inductive reactance from phase separation can lead to a lower power factor, which makes the electrical system less efficient. Utilities may penalize customers with low power factors.

Why Multi-Conductor Cables and Raceways are Preferred

Electrical codes and engineering best practices require all phase conductors (A, B, C, and neutral, if applicable) to be installed together in the same cable, raceway (conduit), or enclosure. This achieves:

Magnetic Field Cancellation

The magnetic fields produced by the different phase conductors largely cancel each other out, reducing inductance and eddy current losses.

Lower Impedance

The overall impedance of the circuit is minimized, resulting in lower voltage drop, lower power loss, and improved system performance.

Improved Safety

The risk of inductive heating, energized conduit, and arc flash hazards is greatly reduced.

Code Compliance

It satisfies the requirements of electrical codes like the NEC, CEC, and others.

Simplified Installation

It's generally more efficient and cost-effective to run all conductors together in a single raceway or cable.

In summary, while it might seem logical at first glance to separate phases into different conduits, the electrical and safety consequences of doing so are significant and unacceptable. It violates electrical codes and leads to a dangerous, inefficient, and unreliable electrical system. Flag for review