What is the difference between the cell capacity and rated capacity of charger?

The rated capacity of the transformer is the maximum output that can be continuously output during the specified normal service life, such as 30 years. The actual output capacity is the voltage at the time of load (inductive load, the voltage at load is less than the rated no-load voltage), and the product of the rated current and the corresponding coefficient.

Conceptual interpretation

The rated capacity is the usual value of the apparent power under the main tap. The capacity specified on the transformer nameplate is the rated capacity. It means that the tap changer is located at the main tap and is the product of the rated no-load voltage, rated current and the corresponding phase factor. For three-phase transformers, rated capacity = rated no-load line voltage × rated line current, rated capacity is generally expressed in kVA or MVA. The rated capacity is the continuous output of the maximum capacity during the specified normal service life, such as 30 years. The actual output capacity is the voltage at the time of load (inductive load, the voltage at load is less than the rated no-load voltage), and the product of the rated current and the corresponding coefficient.

For the unloaded voltage regulating transformer, the rated capacity can be output at the -5% tap position, and the output capacity is reduced when the tap position is below -5%.

For on-load tap-changers, the general manufacturer has specified that the rated capacity can still be output at the -10% tap position, and the rated capacity is reduced when the tap position is below -10%. All of the above are for constant flux regulation, power transformers or distribution transformers. For a variable-transformer piezoelectric furnace transformer or a rectifier transformer, the rated capacity refers to the maximum output capacity, and the output capacity at most tap positions is less than the rated capacity.

The actual situation

In actual operation, the transformer also has a load capacity, and the additional load capacity is by no means the load capacity of the transformer. Load capacity refers to the actual capacity value that the transformer can output only for a certain time interval that is confirmed. This capacity value is determined by the operating conditions of the transformer within the identified time interval, or by whether it damages its normal service life, whether it increases the natural aging of its insulation, and whether it compromises the safe operation of the transformer. The load capacity can exceed the rated capacity, but the load capacity has an upper limit, that is, the hot spot temperature of the winding cannot exceed 140 °C. When the temperature exceeds 140 °C, the oil near the hot spot temperature of the winding is decomposed into gas, which affects safe operation, and the hot spot temperature of the winding does not exceed At 140 ° C, when the oil temperature exceeds 120 ° C, the field strength of the oil will be affected by the combined action of heat and electricity. When the winding hot spot temperature exceeds 98 °C, it will affect the service life of the transformer.

Due to the need for first aid, the actual load capacity of the transformer can exceed the rated capacity, but to ensure that the hot spot temperature of the winding cannot exceed 140 °C, the service life at the sacrifice should be compensated by the increased life when operating below the rated capacity. When the first-aid operation exceeds the brand-name capacity, the load loss is much higher than the rated load loss. The output voltage under load is much lower than the rated no-load voltage and the efficiency is also poor.

The rated capacity of the autotransformer is the pass capacity, and the true structural capacity is much smaller than the rated capacity. Only part of the output capacity of the autotransformer is the capacity of the electromagnetic induction in the past, and part of the output capacity is directly passed.

The rated capacity of a three-winding transformer is generally expressed as a percentage of the rated capacity of each winding. For example, 100%/100%/100% means that each winding can reach the rated capacity, and 100%/100%/60% means that the low-voltage winding only Can reach 60% of rated capacity.

The low-voltage windings of the autotransformer generally do not reach the rated capacity. For example, when expressed in 100%/100%/50%, the low-voltage winding can only reach 50% of the rated capacity.

In addition, when a transformer has several cooling methods, the rated capacity refers to the maximum capacity, and the output capacity is changed when the cooling mode is changed.

When a transformer has three different cooling conditions, such as forced oil circulating air cooling, oil immersed air cooling, oil immersed natural cooling, three different cooling conditions, the rated capacity corresponding to each cooling method is expressed as a percentage. When, it is 100%/80%/60%. When forced oil circulation air-cooling, it can output 100% of rated capacity. When the cooling pump is shipped, it can output 80% of rated capacity under oil-immersed air-cooling. When the pump is shut down, the output capacity should be reduced by 20%. When cooling pump and cooling fan When they are out of service, they can not only output 60% of rated capacity for oil immersion from cold, that is, when the pump and fan are out of service, the output capacity is reduced by 40% of rated capacity.

The corresponding output capacity under different cooling conditions is related to the structure of the cooling device. Some structures of the cooler can only be operated under forced oil circulation and air cooling. When the pump is deactivated, the output capacity should be reduced to zero in a short time. The capacity of three different cooling modes of 100%/80%/60% refers to the radiator type cooling device plus the pump and the fan.

Transformers operating in three different cooling conditions can have three rated capacities, but performance parameters are based on the maximum rated capacity. The rated capacity of each cooling method is based on the temperature rise not exceeding the specified limit.

Battery capacity is one of the important performance indicators to measure battery performance. It indicates the amount of electricity discharged by the battery under certain conditions (discharge rate, temperature, termination voltage, etc.) (Discharging test can be performed with JS-150D), that is, the capacity of the battery, usually Ampere·hour is the unit (abbreviated as A·H, 1A·h=3600C).

The battery capacity is divided into actual capacity, theoretical capacity and rated capacity according to different conditions. The calculation formula of battery capacity C is C=∫t0It1dt (integration of current I from t0 to t1), and the battery is divided into positive and negative poles.

The battery capacity is divided into actual capacity, theoretical capacity and rated capacity according to different conditions.

The minimum capacity to be discharged at a certain discharge rate at 25 ° C to the termination voltage is the capacity of the specified battery at the time of design and production. This is called the rated capacity of a certain discharge rate RH.

Square lithium ion battery

Square lithium ion battery

The battery capacity is generally calculated in AH (ampere-hours), and the other is calculated in CELL (unit plate) several watts (W). (W/CELL)

1. Ah (ampere hour) calculation, discharge current (constant current) I × discharge time (hour) T. For example, if the 7AH battery has a continuous discharge current of 0.35A, the time can be continuous for 20 hours.

2. The charging time is based on 15 hours, and the charging current is 1/10 of the battery capacity. Fast charging will reduce battery life.

Battery capacity refers to the amount of battery storage. The unit of battery capacity is “mAh”, and the Chinese name is mAh (when measuring a large-capacity battery such as lead storage battery, for the sake of convenience, it is generally indicated by “Ah”, the Chinese name is Anshi, 1Ah=1000mAh). If the rated capacity of the battery is 1300mAh, that is, the current of 130mA discharges the battery, the battery can work for 10 hours (1300mAh/130mA=10h); if the discharge current is 1300mA, the power supply time is only about 1 hour (actual working time) There are some differences due to individual differences in the actual capacity of the battery). This is an analysis under ideal conditions. The current when the digital device is actually working cannot always be constant at a certain value. (In the case of a digital camera, the operating current will be large due to the opening or closing of components such as the LCD display and flash. Change), so the battery can only provide a certain value for the power supply time of a device, and this value can only be estimated through practical experience.

Usually we say that the battery capacity is in ampere-hours, which is based on a certain battery that has been determined.

For example, we say the battery capacity of this mobile phone; the battery capacity of this battery car is different for different batteries. For the battery voltage has been determined, without considering the actual voltage, it is only necessary to say that the battery capacity can be represented.

However, for batteries of different voltages, we can't simply use Anshi to represent the capacity, such as a 12V20AH battery, a 15V20AH battery, even 20AH, supply the same power load, the equipment can work normally, but the duration is Not the same, so the standard capacity should be in work.

For another example, a device can support 12V and 24V. It can be powered by a 12V (20AH) battery and can provide one hour. Then two series will become 24V (20AH). The time will be doubled, so the capacity should be considered as the work contained in the battery at this time, and it should not be considered simply.

W (work) = P (power) * T (time) = I (current) * U (voltage) * T (time)

This discussion of battery capacity has practical significance, and must be realistic. Otherwise there may be a saying that a mobile phone battery is larger than the battery capacity of a battery car, which is obviously unscientific.