low voltage transformer
The following is a detailed guide on the **Low Voltage Transformer**, covering definitions, types, applications, prices, and key points for selection:
I. Core Definitions and Voltage Ranges
A **low voltage transformer** refers to a transformer with a secondary output voltage ≤ 1000V. Common voltage levels include:
- **Single-phase**: 120V, 230V, 240V (such as 120V/240V household electricity in the United States)
- **Three-phase**: 208V, 400V, 480V (such as converting 480V to 208V in industry)
**Note**: It is different from high voltage transformers (secondary ≥ 1kV, such as a distribution transformer converting 10kV to 400V).
II. Main Types and Characteristics
1. Classification by the Number of Phases
| Type | Application Scenarios | Common Voltage Combinations | Price Range (US Market) |
| Single-phase | Homes, shops, small equipment (such as lighting, air conditioners) | 240V ↔ 120V, 230V ↔ 110V | $50 – $500 |
| Three-phase | Industrial equipment, factory power distribution | 480V ↔ 208V, 380V ↔ 220V | $150 – $2,000 |
2. Classification by Cooling Method
| Type | Characteristics | Typical Applications | Price |
| Dry-type Transformer | Oil-free, fireproof, low noise, suitable for indoor use | Commercial buildings, data centers, medical equipment | $80 – $1,500 |
| Oil-immersed Transformer | Good heat dissipation by oil cooling, resistant to high voltage, suitable for outdoor use | Outdoor power distribution, industrial heavy equipment | $500 – $3,000 |
3. Special Function Types
- **Isolation Transformer**:
- Characteristics: Electrical isolation between the primary and secondary sides, preventing electric shock and resisting interference (such as for medical equipment, laboratories).
- Price: $200 – $1,000 (single-phase); $500 – $2,500 (three-phase).
- **Autotransformer**:
- Characteristics: Small in size, low in cost, only requiring a single winding (suitable for fine voltage adjustment, such as 220V ↔ 240V).
- Price: $30 – $300 (small power single-phase).
- **Toroidal Transformer**:
- Characteristics: High efficiency (90%+), low noise, suitable for precision electronic equipment (such as audio systems, power supplies).
- Price: $100 – $800 (100VA – 10kVA).
III. Application Scenarios and Recommended Models
| Scenario | Recommended Type | Typical Voltage | Examples of US Brands | Price |
| Home Power Supply (converting 240V to 120V) | Single-phase dry-type/Autotransformer | 240V ↔ 120V | Wankong D, Eaton | $50 – $200 |
| Commercial Lighting (converting 120V to 24V low-voltage lights) | Single-phase dry-type (step-down) | 120V ↔ 24V | Wankong, Leviton | $20 – $100 |
| Industrial Equipment (converting 480V to 208V) | Three-phase dry-type | 480V ↔ 208Y/120V | ABB, Schneider | $300 – $1,500 |
| Outdoor Security (powering 12V cameras) | Single-phase miniature transformer | 120V ↔ 12V | Wankong | $10 – $50 |
IV. Key Selection Factors
1. **Voltage Matching**:
- Commonly used in the United States are **120V/240V single-phase** and **208Y/120V three-phase** (pay attention to phase balance).
2. **Capacity Calculation**:
- Formula: `Transformer Capacity (kVA) = Total Load Power (kW) ÷ Power Factor` (generally taken as 0.8).
- Example: An 8kW load requires at least a **10 kVA** transformer.
3. **Protection Level**:
- Indoor: IP20 (dustproof); Outdoor: IP65 (waterproof and dustproof, such as streetlight transformers).
4. **Certification Standards**:
- In the United States: **UL 1561** (dry-type), **UL 1096** (oil-immersed), **NEC Article 450** (installation specifications).
- Internationally: CE (IEC 61558), GB 19212 (China).
V. Installation and Maintenance
- **Installation Precautions**:
- Dry-type transformers require good ventilation, and oil-immersed transformers need to be kept away from fire sources and equipped with oil leakage protection.
- According to US regulations: The transformer should be at least ≥ 1.8 meters away from combustibles (outdoor), or use a fireproof casing (indoor).
- **Maintenance Cycles**:
- Dry-type: Check the windings and fans every year and clean the dust;
- Oil-immersed: Change the oil every 2–3 years and check the withstand voltage value of the insulating oil.
VI. Price Summary and Purchase Suggestions
- **Budget Range**:
- Small power for household use (<1kVA): **$10 – $200**;
- Industrial-grade 10kVA three-phase: **$300 – $2,000**.
- **Cost-effective Brands**:
- Domestic brands in the US: Wankong electrical
- International brands: Mean Well (switching power supply transformers), Tamura (toroidal transformers).
- **Purchase Channels**:
- E-commerce: Wankong electrical (industrial-grade);
- Local: Electrical wholesalers (such as Graybar), which provide installation services.
Tips**: Low voltage transformers should avoid overload. Exceeding the rated capacity for a long time will shorten their lifespan. If used for inductive loads (such as motors), a transformer with a capacity **1.2–1.5 times** should be selected.
It should be noted that "Wankong electrical" may need to be further verified according to the actual situation, and you can confirm and correct it as needed.
