Dry-type transformers are widely used in power systems, industrial manufacturing, commercial buildings, and other fields due to their safety, environmental friendliness, and maintenance-free advantages. However, many users often do not fully understand the parameters on the nameplate when selecting and using dry-type transformers, leading to improper selection or reduced operating efficiency. This article will provide a detailed interpretation of the key parameters on the nameplate of dry-type transformers to help you choose and use them correctly, ensuring efficient and stable operation of the equipment.
Detailed Interpretation of Dry-Type Transformer Nameplate Parameters
The nameplate of a dry-type transformer typically includes the following core parameters, each of which has a direct impact on the performance and application scenarios of the transformer:
Rated Capacity (kVA)
Definition: The apparent power that the transformer can output stably over the long term at rated voltage and frequency.
Common Specifications: 30kVA, 50kVA, 100kVA, 200kVA, 500kVA, 1000kVA, etc.
Selection Suggestions: Choose based on load demand to avoid overloading or wasting capacity. For example, commercial buildings may select 100kVA to 500kVA, while large factories may require more than 1000kVA.
Rated Voltage (kV)
Definition: The nominal voltage of the transformer's input (high-voltage side) and output (low-voltage side).
Common Specifications:
High-Voltage Side: 10kV, 35kV (commonly used in China)
Low-Voltage Side: 0.4kV (400V, suitable for most low-voltage distribution systems)
Selection Notes: It must match the grid voltage to prevent equipment damage due to voltage mismatch.
Rated Current (A)
Definition: The input and output current of the transformer at rated capacity.
Calculation Formulas:
High-Voltage Side Current (A) = Rated Capacity (kVA) / (√3 × High-Voltage Side Voltage (kV))
Low-Voltage Side Current (A) = Rated Capacity (kVA) / (√3 × Low-Voltage Side Voltage (kV))
Application Significance: Used to select matching circuit breakers, cables, and other equipment.
Frequency (Hz)
Definition: The grid frequency for which the transformer is designed. The domestic standard is 50Hz.
Note: If used in foreign countries (e.g., 60Hz regions), special customization is required.
Insulation Class
Definition: The temperature resistance capability of the transformer's insulating materials. Common classes include:
F Class (155℃)
H Class (180℃)
Impact: The higher the insulation class, the stronger the transformer's high-temperature resistance, making it suitable for high-temperature environments.
Cooling Method
Common Types:
AN (Natural Air Cooling)
AF (Forced Air Cooling)
Application Scenarios:
AN is suitable for small-capacity transformers or environments with good heat dissipation conditions.
AF is suitable for large-capacity transformers or enclosed spaces, requiring the installation of fans to assist with heat dissipation.
Short-Circuit Impedance (%)
Definition: The percentage of impedance of the transformer under short-circuit conditions, reflecting its short-circuit resistance capability.
Typical Values: 4% to 6% (distribution transformers), 6% to 10% (large-capacity transformers).
Selection Impact: Excessive short-circuit impedance may cause voltage fluctuations, while too low impedance may increase the risk of short-circuit current.
Connection Group
Definition: Reflects the connection method of the high and low voltage windings of the transformer (e.g., Dyn11, Yyn0).
Common Types:
Dyn11 (suitable for strong harmonic resistance and unbalanced three-phase loads)
Yyn0 (suitable for general distribution)
Selection Suggestions: Dyn11 is recommended for commercial buildings, while industrial loads should be selected based on actual conditions.
Protection Class (IP)
Definition: The dust and water resistance capability of the transformer, such as IP20 (dustproof but not waterproof) and IP54 (dustproof and splash-proof).
Applicable Environments:
Indoor Dry Environments: IP20
Humid or Dusty Environments: IP54 or higher
Noise Level (dB)
Definition: The operating noise of the transformer at rated load.
Standard: Generally, the noise level of dry-type transformers is ≤65dB, and low-noise models can be ≤55dB.
Application Scenarios: In places with high noise requirements such as hospitals and schools, low-noise models should be selected.
How to Choose the Right Dry-Type Transformer Based on Nameplate Parameters?
1. Determine Load Requirements
Calculate the total load power (kW) and consider future expansion needs. Select a transformer with a slightly larger capacity (e.g., if the load is 80kVA, choose a 100kVA transformer).
Pay attention to the load type (e.g., motors, LED lights, frequency converters). In environments with high harmonics, select models with strong harmonic resistance (e.g., Dyn11 connection group).
2. Match Grid Parameters
Confirm the input voltage (e.g., 10kV) and output voltage (e.g., 400V) to avoid voltage mismatch.
Check the frequency (50Hz in China, 60Hz in some countries).
3. Consider Environmental Factors
In high-temperature environments, select models with H-class insulation or forced air cooling (AF).
In humid or dusty environments, choose models with a higher protection class (e.g., IP54).
4. Focus on Energy Efficiency Standards
Domestic dry-type transformers are classified into three energy efficiency levels: Level 1 (highest), Level 2, and Level 3. Prefer Level 1 energy efficiency to reduce operating costs.
Advantages and Application Scenarios of Dry-Type Transformers
1. Advantages
Safety and Environmental Friendliness: Oil-free, no fire risk, suitable for high-rise buildings, subways, and other places.
Maintenance-Free: No need to regularly replace insulating oil, reducing maintenance costs.
Energy-Saving and Efficient: Low losses due to the use of high-quality silicon steel sheets and copper windings.
2. Typical Applications
Commercial Buildings: Shopping malls, office buildings, hotels (100kVA to 800kVA).
Industrial Fields: Factories, mines, petrochemicals (500kVA to 2500kVA).
New Energy: Photovoltaic power stations, wind power generation (with step-up transformers).
The nameplate parameters of dry-type transformers directly affect their performance and service life. Correctly understanding and selecting the appropriate parameters is crucial. Through the interpretation provided in this article, it is hoped that you can more clearly grasp the key points of selecting dry-type transformers to ensure the efficient and stable operation of the power system.
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