Application issue regarding the external power capacity for the new factory site

Depending on the nature of the workshop, the demand factor varies significantly between continuous and intermittent production. You can look for workshops of the same type as a reference. The calculated power, when converted to apparent power, is the transformer capacity you need to declare. Of course, don’t forget to reserve capacity and take future factors into account as well.

First of all, thank you for your answer. But I still have some questions and hope you can answer them. Generally, factory equipment operates on a continuous basis; the capacity Pe of such equipment is obtained by adding up the values indicated on the nameplate, with an assumed total of 6208 kW. The calculated total active power is P30 = Kd × Pe = 0.9 × 6208 = 5588. Here, Kd is assumed to be 0.9; this coefficient takes into account the fact that not all devices in the same group operate simultaneously, and those that do operate may not all be under full load. The apparent power S30 is then calculated as S30 = P30 / cosφ = 5588 / 0.85 = 6573 kVA. Generally speaking, this value of 6573 kVA can be used when applying for external power supply capacity. But if there is a large compressor unit, should the capacity required of the other compressor when it takes over be considered? Or in the case of abnormal conditions where two or more large units are operating simultaneously, whether such a calculated capacity is still sufficient. Suppose there is a 2000 kW large compressor that needs to be taken out of service; for a certain period of time, there will thus be a higher capacity available. Is it necessary to take this capacity resulting from the compressor being taken out of service into account? Is it to consider the capacity required for machine shutdown based on calculations?

In the formula S30 = P30/cosφ, consideration must be given to the economic operation of transformers; they are not operated at full load. Therefore, a coefficient, such as 0.8, needs to be divided into the calculation. In the special circumstances you mentioned, it depends on whether your equipment is in cold standby or hot standby mode. When in hot standby mode, the capacity also needs to be taken into account; don’t forget to consider electricity usage during peak, off-peak, and valley periods. 2000KW equipment will use high-voltage motors

This post was last edited by chadengsheng on 2017-9-23 at 11:15. The examples I gave earlier were obtained by simply adding up all the powers; in such cases, I believe it’s not necessary to take into account the transformer coefficient. If the transformer coefficient is considered, it’s because the transformer doesn’t operate at full load, but rather at around 80% of its capacity. It might even be smaller. A 2000kw motor is definitely a high-voltage motor. Because all the above formulas only discuss the capacity required for the equipment to operate under normal conditions. However, the capacity required in case a shutdown is necessary due to equipment failures has not been taken into account; or perhaps the calculated capacity may be sufficient, but no further assessment has been conducted. So, in my opinion, it is still necessary to take into account the capacity required during the shutdown process, after all, there will be a period of time when the equipment continues to operate simultaneously. In other words, when testing the equipment after maintenance, it is also necessary to consider the capacity of the system to accommodate devices with the highest power levels operating simultaneously. It’s a bit different from your view. I agree with you that hot standby definitely needs to be taken into consideration, but for cold standby devices, I think the capacity of the device with the highest power output should also be factored in (when applying for external lines)

If you are considering the need to turn on the backup equipment in case of an emergency and are worried that the transformer’s capacity may not be sufficient, then estimate the probability of such backup operation being required, as transformers can handle short-term overloads