A transformer changes alternating current (AC) voltage from one level to another for power companies, appliances and chargers. But the size of a transformer has little to do with the voltage, and everything to do with the amount of electricity it provides. Electricians and technicians refer to the equipment a transformer powers as its load, be it machinery, appliances or electronic components. The load can be measured in amps, watts or volt/amps. To calculate load, you must understand certain electrical terms and formulas.

- Skill level:
- Easy

### Other People Are Reading

### Things you need

- Pen or pencil
- Notepad

Show More

## Instructions

- 1
Inventory all the equipment the transformer powers. Make a list of the components, lights, appliances or machinery that the transformer will operate. Add the amount of current, watts or volt/amps that each draws. There should be a tag or label on all equipment telling the amount of current or power it draws.

- 2
Convert the power to equivalent values. Arrange the values into two columns on the list. Label the first "current" and the second "watts" or "volt/amps." Use the formula power equals volts times amps, or (P=IE) t, make conversions.

- 3
Add up the total current in amps for the first column and the watts or volt/amps in the second column. The sums equal the transformer load expressed in the three terms.

#### Tips and warnings

- The prefix "milli" means thousandths and "kilo" means thousands. For example, 50 milliamps equals .05 amps, 10kW means 10,000 watts and 5 kVA means 5,000 volt/amps.
- Volt/amps and watts actually mean the same thing because wattage equals volts times amps.
- Don't add watts to kilowatts without converting to equivalent values. For example, 10kW plus 100 watts equals 10.1kW or 10,100 watts.
- Don't add amps to watts. Make the conversions first, and only add amps to amps and watts to watts.