To calculate how long a 27 Watt cooling fan will run on a 30000 mAh power bank

 To calculate how long a 27 Watt cooling fan will run on a 30000 mAh power bank, you can use the following formula:

Time (hours) = Battery Capacity (mAh) / Device Power (mAh)

First, you need to convert the power bank's capacity from mAh to Wh (Watt-hours) because the fan's power is given in Watts.

Battery Capacity (Wh) = Battery Capacity (mAh) / 1000 * Battery Voltage

Assuming the power bank voltage is around 3.7V (common for lithium-ion batteries), you can calculate the Wh as follows:

Battery Capacity (Wh) = 30000 mAh / 1000 * 3.7V = 111 Wh

Now you can calculate the runtime of the fan:

Time (hours) = 111 Wh / 27 Watts ≈ 4.11 hours

So, the power bank will take approximately 4.11 hours to go from 100% to 0% when powering the 27 Watt cooling fan continuously. Keep in mind that this is a theoretical estimate, and actual runtime may vary depending on factors like the efficiency of the power bank and the fan.  

why we use 230v in single phase and 415v in three phase system.

This video explains about the Indian Electrical Voltage standards and also answer the below mentioned questions. 1. Why we use 3 phase system. 2. why we use 415V in 3 phase system. 3.why we use 230v in single phase system. 4. why we use square root 3 in electrical calculation. 5. Different btn line and phase voltage. 6. Indian secondary distribution system voltage.