Transformers are "transit stations" in the power system, responsible for the efficient transmission of electrical energy between different voltage levels. Whether it is industrial production, urban construction, or access to new energy, it is inseparable from it. When purchasing or operating and maintaining, the four parameters of capacity, voltage, loss, and impedance are the most basic and important judgment basis.
Interpretation of transformer parameters
Definition: The maximum apparent power that the transformer can output under long-term stable operating conditions.
Significance: It determines how much electrical load the transformer can carry.
Precautions:
·The capacity unit is kVA, not kW. The actual available power needs to be multiplied by the power factor (generally 0.8~0.95).
·Long-term full load will accelerate the aging of insulation. It is recommended to reserve a margin of about 20%.
Application recommendations: Industrial users should consider peak production, and commercial users should combine comprehensive loads such as air conditioning and lighting.
02 Voltage (kV/V)
Definition: The rated voltage of the transformer design and operation, such as "10±2×2.5%/0.4kV".
Interpretation:
·High voltage side: 10 kV, which is the input voltage.
·Low voltage side: 0.4kV (400 V), used for industrial and civil power distribution.
·Tap gear: ±2×2.5% means that there are 5 gears of voltage regulation, which can be adjusted when the grid voltage fluctuates.
·Operation and maintenance tips: Check the tap switch regularly to ensure that the voltage is within a safe range to avoid damage to the back-end equipment.
There are two types of losses when the transformer is running：
·No-load loss (iron loss): Caused by the magnetization of the iron core and eddy currents, it exists as long as it is energized and has nothing to do with the load.
·Load loss (copper loss): The resistance loss caused by the current passing through the winding varies with the load.
Impact: Loss is directly related to operating electricity bills, and it is also the core index of energy efficiency rating.
Energy-saving recommendations: Give priority to products that meet the first-level energy efficiency standards. Although the initial investment is slightly higher, the long-term savings in electricity bills are considerable.
04 Impedance (short circuit impedance %)
Definition: The equivalent impedance of the transformer in the short-circuit state as a percentage of the rated voltage.
Effect：
·Limit short-circuit current and protect switching equipment and cables.
·Affect voltage stability: the higher the impedance, the greater the voltage fluctuation when the load changes; the lower the impedance, the greater the short-circuit current.
Selection reference:
·Urban distribution network: use 4% to 6% more, taking into account safety and voltage quality.
·Heavy industry: higher impedance can be selected to cope with the start-up impact of large motors.
