When selecting a servo voltage stabilizer, the cooling method is one of the most important decisions after capacity. Both air cooled and oil cooled designs achieve the same result — stable output voltage — but differ significantly in their construction, performance, and suitability for different environments.
How Each Cooling Method Works
flowchart LR
subgraph AC["🌬️ Air Cooled"]
direction TB
A1["Heat generated
in windings"] --> A2["Fans circulate
cool air"] --> A3["Heat dissipated
through vents"]
end
subgraph OC["🛢️ Oil Cooled"]
direction TB
B1["Heat generated
in windings"] --> B2["Transformer oil
absorbs heat"] --> B3["Oil radiates heat
through tank walls"]
end Air Cooled: Uses fans to circulate ambient air through the enclosure, removing heat from the windings. Simple, lightweight, and compact.
Oil Cooled: The transformer and variac are submerged in mineral/transformer oil inside a sealed tank. Oil absorbs heat from windings and dissipates it through the tank surface. Far more efficient at higher capacities.
Full Comparison Table
| Feature | Air Cooled | Oil Cooled |
|---|---|---|
| Cooling Method | Forced air (fans) | Transformer oil (ONAN) |
| Capacity Range | 1 kVA – 300 kVA | 50 kVA – 2000+ kVA |
| Installation | Indoor only | Indoor or outdoor |
| Maintenance | Fan cleaning, dust removal | Oil level check, periodic oil testing |
| Cost | Lower for small capacities | More economical at high capacities |
| Ambient Temperature | Up to 45°C | Up to 55°C+ |
| Noise Level | Fan noise present | Very quiet (no fans) |
| Weight | Lighter | Heavier (oil mass) |
How to Choose
flowchart TD
Start([Start: What is your load?]) --> Q1{Load above 100 kVA?}
Q1 -->|Yes| Rec1["✅ Oil Cooled
More efficient at scale"]
Q1 -->|No| Q2{Outdoor installation?}
Q2 -->|Yes| Rec2["✅ Oil Cooled
Weather-resistant sealed tank"]
Q2 -->|No| Q3{Ambient temp above 45°C?}
Q3 -->|Yes| Rec3["✅ Oil Cooled
Better thermal performance"]
Q3 -->|No| Q4{Noise-sensitive area?}
Q4 -->|Yes| Rec4["✅ Oil Cooled
No fan noise"]
Q4 -->|No| Rec5["✅ Air Cooled
Lower cost, easier maintenance"] Choose Air Cooled if: load is under 300 kVA, installation is indoors, budget is the primary concern, and quick servicing is required.
Choose Oil Cooled if: load exceeds 100 kVA with continuous duty, installation may be outdoors, ambient temperatures are high, or extremely quiet operation is required.
ServoKai Air & Oil Cooled Stabilizers
ServoKai System manufactures both air cooled servo stabilizers (1 kVA – 300 kVA) and oil cooled servo stabilizers (30 kVA – 2000+ kVA) with full copper winding, CRGO core, and ±1% output accuracy. View our full product range →