Let's break down what would happen if two completely isolated generators have their hot legs directly connected, and what the implications are

Understanding "Isolated" Systems

The term "isolated" is key here. It means: No Common Ground/Neutral

The neutral (or derived neutral) of each generator is not connected to earth ground, nor are they connected to each other. This is crucial.

No Shared Load

The generators are powering independent loads with no electrical connection between those loads.

Scenario: Hot Leg to Hot Leg Connection

Here's what would occur if you directly connect the hot (live) leg of Generator A to the hot leg of Generator B:1. Voltage Difference is Key

The most important factor is the instantaneous voltage difference between the two hot legs at the moment of connection. Generators are rarely perfectly synchronized. Even if they are "trying" to produce the same voltage, there will almost always be a slight phase angle difference, causing a voltage difference.2.

Current Flow (Potentially Large)

This voltage difference will cause a current to flow between the two generators. The magnitude of this current is determined by:

The Voltage Difference

A larger voltage difference means a larger current.

The Internal Impedance of the Generators

Generators have internal resistance and reactance (impedance). This limits the current flow. Smaller generators have lower impedance, and thus more current.3.

Harmonics, Feedback, and Synchronization

If the generators are inverter generators, the inverters may attempt to synchronize. Inverter generators should never be run in parallel unless specifically made to do so.4.

No Direct Path Back to Source (But Still a Path)

You're right that there's no direct path back to the source in the traditional sense (like a neutral wire). However, the current will flow through the internal windings and impedances of both generators. It's a loop formed by: Hot leg of Generator A Connection between hot legs Hot leg of Generator B Internal windings of Generator B Internal windings of Generator A5.

Potential Consequences



Generator Damage

The circulating current can overheat the generator windings. Depending on the magnitude and duration, this can lead to insulation breakdown and permanent damage. Smaller generators are more vulnerable.

Voltage Instability

The current flow can cause voltage fluctuations in both systems.

Mechanical Stress

The electromagnetic forces within the generators will be affected, potentially leading to mechanical stress.

Arcing at Connection

If the connection is loose or intermittent, you'll get arcing, which can cause further damage and potential fire hazards.

Why No Current Flow Isn't Likely

You asked if there would be no current flow. This is highly unlikely for the following reasons: Perfect Synchronization is Impossible

Even with sophisticated synchronization equipment, it's virtually impossible to get two generators to produce exactly the same voltage at exactly the same phase angle at all times.

Transient Events

Small fluctuations in load or engine speed will cause momentary voltage differences.

Inverter Generators will cause problems

Even if they are both set to the same nominal output frequency, the inverters will not synchronize. Inverter generators will try to adjust and damage themselves in short order.

In Summary

Connecting the hot legs of two isolated generators will result in current flow due to the inevitable voltage difference. The magnitude of the current depends on the voltage difference and the internal impedance of the generators. The result will be detrimental to both generators. Flag for review