kVA (kilovolt-ampere) is the unit of apparent power, and kW (kilowatt) is the unit of active power. In addition to apparent power and active power, there is also reactive power. The unit of reactive power is kvar (kilovar). What is the difference between active power, reactive power, and apparent power?
Active power is the power actually consumed by electrical appliances, that is, the conversion of electrical energy into other forms of energy.
Reactive power refers to some equipment that does not really consume electricity, it is only the part of power that temporarily stores electricity.
Apparent power refers to the total power provided by the power supply.
cosφ=P/S
Power factor refers to the ratio of active power to apparent power, generally expressed by cosφ.
For example, a 1000kVA transformer, when the power factor cosφ=0.6, it can output 600kW of active power; but when the power factor cosφ=0.9, it can output 900kW of active power.
The capacity unit of the transformer is kVA (kilovolt-ampere), while the power unit of the electrical equipment is kW (kilowatt). The difference between the two is that the power factor needs to be multiplied when calculating the power kW of the equipment, that is, a transformer with a capacity of 1000kVA. Only when the power factor is 1, it can output 1000kW of power at full load, but it is basically impossible in practical applications.
When designing, it is necessary to leave a certain margin, which is generally calculated according to a 90% coincidence rate, which is more economical and reasonable, that is, 1000×0.9=900kVA. If we compensate the power factor to 0.95 or above through power compensation, then the transformer can output 900×0.95=855kW active power.
The 1000kVA transformer originally supplied power to the 200kW electrical equipment, and now 600kW electrical equipment has been added. The total active power of the electrical equipment has reached 800kW, which still does not exceed the calculated value.
Therefore, the 1000kVA transformer originally supplied power to the 200kW electrical equipment, and now 600kW electrical equipment has been added. As long as we can increase the power factor to the required value, the transformer can fully operate safely for a long time.
