What are the standard sizes of transformers?
Transformer sizes are standardised across the industry to promote compatibility, interchangeability and easy replacement in electrical systems, and colleagues to facilitate production by manufacturers and selection by users.
1.Distribution transformer ratings:
– 480 volt to 120/208 volt transformers: 15, 30, 45, 75, 112.5, 225, 300 and 500 kVA.
– Single-phase 277 or 480 volt transformers: 5, 7.5, 10, 15, 25, 37.5, 50, 75, and 100 kVA.
2.Transformer types and ratings:
– Enclosed transformers: ratings generally range from 50VA to 25kVA.
– Ventilated single-phase transformers: ratings are usually slightly higher, usually from 25 to 100 kVA.
– Enclosed three-phase transformers: ratings typically range from 3-75 kVA.
– Vented three-phase transformers: ratings are considerably higher than encapsulated three-phase transformers, sometimes exceeding 1,000 kVA.
– Enclosed non-ventilated transformers: the relevant ratings are usually 25-500 kVA.
When selecting a transformer, in addition to its size and power rating, it is important to consider the transformer’s efficiency, temperature rise, noise level, installation environment and other application-specific requirements. Proper selection of a transformer is critical to ensuring the reliability and efficiency of your power system.
What are standard LV transformer sizes?
Low-voltage transformers are mainly used for residential and commercial purposes to reduce the risk of electrocution and short-circuiting to users. They play a vital role in ensuring safety and preventing potential hazards associated with high voltage electricity. According to ANSI Standard C84.1-1989, operating voltages are divided into five categories to facilitate the selection of the right transformer for the application:
– Low voltage: less than 600V
– Medium voltage: 600V to 69kV
– High voltage: 69kV to 230kV
– Extra high voltage: 230kV to 1100kV
– Extra high voltage: 1100kV
Transformers can be divided into the above five types according to their operating voltage, for example, step-up transformers with an operating voltage of 12.8kV to 128kV belong to high-voltage transformers, and step-down transformers with an operating voltage of 230V to 14V belong to low-voltage transformers.
The mains voltage and frequency of different countries are different, for example, the mains voltage of the United States and other national standards is 120V and the frequency is 60Hz, while the mains voltage of the United Kingdom, the Netherlands, Germany and other European countries is generally 230V and the frequency is 50Hz.
What is the capacity of a dry type transformer?
The capacity of dry-type transformers is measured in kilovolt-amperes (kVA) and varies greatly depending on their specific use and design. However, dry-type transformers are generally available in the range of 30 kVA to 40,000 kVA.
Standard dry-type transformer capacities are:
Small Transformers: 30 kVA to 500 kVA, typically used for residential, commercial and industrial applications with lower power requirements.
Medium transformers: 500 kVA to 5,000 kVA, for large commercial and industrial buildings, data centres and manufacturing facilities.
Large transformers: 5,000 kVA to 40,000 kVA for high-power industrial applications, substations and power transmission systems.
The capacity of a dry-type transformer depends on a number of factors, and calculating the capacity of a dry-type transformer involves determining its ability to handle the electrical load it will be subjected to. The primary unit of measurement for transformer capacity is the kilovolt-ampere (kVA), which represents the product of the transformer’s primary voltage and current.
The basic formula for calculating the capacity of a dry-type transformer is:
kVA = (P x 1000) / V
Which:
– kVA is the transformer capacity in kVA
– P is the transformer’s load power, in watts (W)
– V is the transformer primary voltage in volts (V).
Example calculation
Assuming a dry-type transformer with a primary voltage of 480 V and a load power requirement of 10 kW, to determine its capacity in kVA, we can use the following formula:
kVA = (10,000 W x 1000) / 480 V = 20.83 kVA
The transformer therefore has a capacity of 20.83 kVA, which indicates that it is capable of handling a load of 10 kW at 480V.
In addition to the basic formula, other factors that may affect the transformer’s capacity must be considered:
– Core size: The size of the core, made of oriented or silicon steel, determines the transformer’s ability to handle magnetic flux and ultimately its power handling capacity.
– Winding design: The number of turns and wire gauge of a transformer’s windings affect its voltage regulation, efficiency and total capacity.
– Cooling method: The method of cooling, such as natural air cooling, forced air cooling or oil immersion cooling, plays a vital role in dissipating heat and determining the permissible load capacity of the transformer.
