Lets, talk about frequency, or Hertz (Hz). This is the number of times something happens a second. So, if I hit a drum twice a second then it has a frequency of 2 Hz. With AC power the frequency is the number of times the power goes from zero voltage to positive voltage, then to zero voltage, then to negative voltage, then back to zero where it started, ready to go positive again. (This is called a sine wave). In the US we use 60Hz power 120V, with larger appliances using 240V 60Hz. Other parts of the world use 230V 50Hz power. You can use a transformer to convert between voltages, so a 2:1 step-up transformer can input 120V and output 240V. (Most appliances can use voltages +/– 10 to 15V from there nominal voltage, without damage.) You can NOT easily change the frequency of AC power; the simplest way is to convert it to DC then use a inverter to convert it back to AC with the frequency you need.
Outback Power Inverters (and other inverters) are designed to output one frequency either 50 or 60Hz. The newer Outback FXR models allow the output frequency to be changed via advanced settings, although this is not recommended under most circumstances. The voltage can NOT be changed outside of a small range centered around 120V or 230V depending on the specific model. So, if you have a 230V Outback FXR inverter you can output 230V 50Hz or 240V 60Hz, but not 120V. The voltage AND frequency of your generator MUST match the voltage AND frequency of your inverter. The inverter will reject any power outside of its voltage (+/- 20 to 60V) or frequency (+/- 4 to 6Hz) range.
Generators produce AC power by rotating a magnetic field through coil of wire, the actual speed of the rotation is what dictates the output frequency. In the US most of the smaller generators are two poles. So for a frequency of 60Hz (times per second) they have to run at a RPM of = 60Hz * 60 sec/min * 2/2 poles = 3,600RPM. While 50Hz generators must rotate at 50Hz * 60 sec/min * 2/2 poles = 3,000RPM. Larger diesel generators often have four poles so they can run slower and take advantage of the better operating characteristics of diesel motors therefore the RPM = 60Hz * 60 sec/min * 2/4 poles = 1,800RPM and 1,500 RPM for 50Hz. Inverter generators operate differently and are outside of this discussion.
A large category of AC motors speed in RPM, is just under the voltage’s frequency. As an example, a four pole AC motor powered by 120V 60Hz, will run slower than = 60Hz * 60sec/min * 2/4 poles = 1,800RPM. (The actual speed depends on motor design and load but is normally around 1,550 – 1,350 RPM) A two pole AC motor powered by 230V 50Hz, will run slower than = 50Hz * 60sec/min * 2/2 poles = 3,000RPM.
How appliances tolerate different voltages and frequencies falls into several groups.
- Universal Voltage and Frequency – these often accept voltages from 100 – 250V AC and 50/60Hz frequency. Some example appliances are some computer chargers, cell phone chargers and some other devices that converter the AC power into DC and have a wide voltage range. You should read the power supply tag or sticker for its required voltage and frequency.
- Universal Frequency – these often accept any frequency and sometimes even DC power, however the voltage must be in the correct range. An example is a universal motor, these are used in appliances that spin faster than 3,600RPM for example some blenders, routers, and angle grinders. Other examples are some crockpots or kitchen appliances with heaters in them, some (not all) drill batteries chargers will operate on 50/60 Hz. Some newer inverter refrigerators or air conditioners can operate at 50/60 Hz but check the specific model. You should read the power supply tag or sticker for its required voltage and frequency.
- Subpar performance Frequency – these will run at the incorrect frequency but not at full capacity or will overheat if used for too long, however the voltage must be in the correct range. An example is some 60Hz 240V table saws running on 230V 50Hz, the voltage is within range and is not a problem, however the 20% reduction in frequency causes the table saw motor to spin slower, will reduce the cutting speed and performance. The motor may also heat up quicker. Another example is when someone uses 230V 50Hz power with 1:2 step-down transformer to get 115V 50Hz power for use with a 120V 60Hz kitchen appliance. The kitchen appliance may run but at reduced speed and performance with additional heating. The last example is a 230V 50Hz air compressor powered by 240V 60Hz, in this example the air compressor will be required to spin 20% faster than designed, and will have to draw extra current due to the extra work required, this will cause extra heat to build up and likely fail in time or trip overload protection in the motor.
- Not Frequency Compatible – these require the correct frequency to operate at. An example would be a transformer or motor designed to only operate at 60Hz. Due to the specifics of the motor or transformer if it is operated at 50Hz it will enter core saturation, draw excess current, and overheat or be damaged. Microwaves, air conditioners, and refrigerators should only be operated on the frequency they are designed for.
- Not Voltage Compatible – these devices will not operate or be damaged if they are run at the incorrect voltage. This is most devices and appliances. If you provide 230V to a 120V appliance the appliance will likely be damaged quickly. If you provide 120V to a 230V appliance, it may fair better, but it can still be damaged from under voltage.
It is not always clear what group a specific appliance will fall under; best practice is to use an appliance with the voltage and frequency it is designed for. Be aware you risk damaging your appliance if you test how it functions under different frequencies.
It is normally recommended that most missionaries use appliances, generators and inverters with the voltage and frequency of their country of service.