Introduction to Commonly Used Transformers
Add time: 2025-07-31
There are many types of transformers—so, what are some commonly used ones? In this article, Zike Transformer Factory will introduce them to you.
1. Common types of transformers:
Dry-type transformers are widely used in applications such as local lighting, high-rise buildings, airports, and CNC machinery equipment at ports. Cooling methods include natural air cooling (AN) and forced air cooling (AF).
Oil-immersed transformers are critical equipment in power distribution systems for industrial, mining enterprises, and residential buildings. They step down the network voltage from 10(6)kV or 35kV to the 230/400V bus voltage used by end-users.
Box-type substations, also known as prefabricated substations, are compact indoor and outdoor electrical distribution systems. They integrate high-voltage switchgear, distribution transformers, and low-voltage distribution units into a single, factory-made unit arranged according to a specific wiring configuration. Emerging as a cutting-edge alternative to traditional civil-engineered substations, box-type substations come in three main types: American-style, European-style, and integrated designs.
2. Characteristic parameters of commonly used transformers:
Rated Capacity: Refers to the output power of a transformer under operating conditions, expressed as apparent power. It is denoted by SN and measured in units such as kVA or VA. For instance, as shown in the figure, SN is 630 kVA. Common transformer capacities include 160 kVA, 200 kVA, 250 kVA, 315 kVA, 400 kVA, 500 kVA, 630 kVA, 800 kVA, 1000 kVA, 1250 kVA, 1600 kVA, 2000 kVA, and more.
Rated voltage refers to the optimal voltage value between the output terminals of a single-phase or three-phase transformer. It is denoted by UN, with units of kV or V. The primary rated voltage is represented as UN1, while the secondary rated voltage is denoted as UN2. For example, as shown in the figure, UN1 = 10 kV and UN2 = 0.4 kV.
Rated current refers to the current flowing through the primary and secondary winding terminals under rated capacity and permissible temperature rise conditions, denoted by IN, with units of kA or A. The primary winding current is represented as IN1, while the secondary winding current is represented as IN2. For example, as shown in the figure, IN1 = 36.36 A and IN2 = 909.33 A.
Rated frequency: The operating frequency specified during transformer design, denoted as fN and measured in Hertz (Hz). In China, the rated frequency is standardized at 50 Hz.
No-load loss, no-load current
No-load loss, also known as iron loss, primarily consists of hysteresis loss and eddy current loss in the core. It is generally believed that the no-load loss of a transformer remains constant regardless of the load size.
Load Loss
Load loss, also known as copper loss, depends on factors such as the material of the windings. The magnitude of load loss during operation varies in direct proportion to changes in the load.
Impedance Voltage (%)
Short-circuit the secondary winding of the transformer, then gradually increase the voltage applied to the primary winding. When the short-circuit current in the secondary winding reaches its rated value, the voltage being applied to the primary side at that moment is measured. This voltage is typically expressed as a percentage of the transformer’s rated voltage. For example, in the figure, Ud = 5.98%.
Connection Group Designation
Based on the phase relationship between the primary and secondary windings of a transformer, the windings can be connected in various configurations, known as the "winding connection group." To distinguish between different connection groups, the clock representation method is commonly used. For example, Dyn11 indicates that the primary winding is connected in a delta configuration, while the secondary winding is connected in a star configuration with a neutral point—and the group number corresponds to 11 o'clock (representing a phase difference of 330°).
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