The Role of Isolation Transformers in Power Distribution Cabinets
The role of **isolation transformers** in power distribution cabinets is to ensure the safe and stable operation of the
system through functions such as electrical isolation and voltage transformation. The following are its core functions
and detailed analysis:
I. Core Functions
1. Electrical Isolation and Cutting off the Grounding Loop
- **Principle**: The primary and secondary windings of the isolation transformer **have no electrical connection**. Energy
is only transferred through electromagnetic induction, preventing the grounding fault of the primary side from being conducted
to the secondary side.
- **Functions**:
- Prevent the formation of a loop through grounding when the human body touches the secondary circuit, reducing the risk
of electric shock (such as during the maintenance of power distribution cabinets).
- Avoid interference between devices caused by grounding (such as signal interference of industrial control devices).
2. Voltage Transformation and Matching
- **Fixed Transformation Ratio**: Most isolation transformers have a **1:1 transformation ratio**, which only provides isolation
without voltage reduction; in special scenarios, the transformation ratio can be customized (such as 220V → 110V).
- **Applications**:
- Adapt to loads of different voltage levels (such as imported equipment requiring a 110V power supply).
- Obtain a low-voltage safe power supply (such as a 24V control circuit) from a high-voltage system (such as 380V).
II. Main Functions
1. Safety Protection
- **Electric Shock Prevention**: When the secondary side is not grounded, the human body touching any single phase will not
form a loop (such as in medical equipment and machine tool control circuits).
- **Interference Prevention**: Isolate noises such as harmonics and surges in the power grid to protect precision equipment
(such as PLCs and frequency converters in power distribution cabinets).
2. Fault Isolation
- When a grounding short circuit occurs on the primary side, the isolation transformer can **limit the spread of the fault current
to the secondary side**, avoiding the chain damage of the equipment in the power distribution cabinet.
3. System Redundancy
- Double isolation transformers can form a **redundant power supply system** (such as one mains power supply + one generator
power supply), improving the power supply reliability of the power distribution cabinet.
4. Lightning Protection and Overvoltage Protection
- When used in conjunction with lightning arresters, it can **suppress lightning strikes or switching overvoltages**, protecting the
insulation of the rear-end equipment (especially for outdoor power distribution cabinets).
III. Typical Application Scenarios
| Scenarios | Function Description |
| Industrial Power Distribution Cabinets | Isolate the power supply for power and control, preventing the start and stop of motors from interfering with PLC signals. |
| Medical Places | Provide a "floating ground power supply" for surgical equipment to avoid medical accidents caused by leakage current (in line with IEC 60601 standards).。 |
| Laboratory Equipment | Isolate power grid noise to ensure the accuracy of test data. |
| Flammable and Explosive Places | Eliminate the hidden danger of grounding sparks and be used in conjunction with explosion-proof power distribution |
IV. Differences from Ordinary Transformers
| Characteristics | Isolation Transformers | Ordinary Transformers |
| Winding Connection | No electrical connection between the primary and secondary sides | Direct coupling between the primary and secondary sides through the iron core |
| Transformation Ratio | Mostly 1:1, other transformation ratios are optional | Fixed transformation ratio (such as 10kV/400V) |
| Main Functions | Electrical isolation and anti-interference | Voltage transformation and energy transfer |
| Grounding Method | The secondary side is usually not grounded (floating ground) | The neutral point of the secondary side must be grounded |
V. Selection Key Points
1. **Power Matching**: Select the capacity according to the total power of the load (reserve 20% redundancy).
2. **Insulation Grade**: Give priority to selecting **double insulation** or **reinforced insulation** types in power
distribution cabinets.
3. **Protection Grade**: Select IP54 and above for outdoor power distribution cabinets, and IP20 for indoor ones.
4. **Noise Requirements**: Low-noise models (<40dB) are required for precision places.
VI. Conclusion
The isolation transformer is a "safety barrier" of the power distribution cabinet. Through electrical isolation, anti-interference,
and voltage matching, it ensures the safety of personnel and the stable operation of equipment. It is indispensable, especially
in scenarios with high requirements for safety and electromagnetic compatibility.
