Why some countries are using 50Hz power supply, while others use 60Hz? What are the advantages and disadvantages of 50Hz and 60Hz power? Do they have effect on the load power?
In fact, the difference between 50 Hz and 60 Hz is not so great, there are no substantive issues. However, the rotational speed of the generator is slightly different. Select 50Hz or 60Hz, in a country, there always is the same except Japan. One thing should be concerned is, why using 50Hz or 60Hz, but not higher or lower frequency.
In the electrical system, the frequency is a very important element which should not be determined arbitrarily.
People sum up the theorem as, periodically changing the direction of current is called alternating current (AC). Generating a periodically varying of time is called frequency, which is measured in hertz (in commemorate the contribution of Hertz). Alternating current frequency is 50 or 60 Hertz, the direction of the current change 50 or 60 cycles per second, the number of changes per second is 100 or 120 cycles.
The frequency is determined by generators, motors and transformers such as construction, materials and so on.
50 Hz bipolar generator synchronous speed is 3000rpm, and if the frequency is doubled to 100 Hz, the synchronous speed will be 6000rpm. This high speed will brought many problems to the generator, especially the line speed of the rotor surface can be too high, which will greatly increase the capacity limit. In addition, from the use of perspective, the frequency is too high, so that the reactance increases, electromagnetic loss, exacerbated the amount of wasted effort. For example, three-phase motor current will be greatly reduced, output power and torque also declined significantly, there is no benefit. In addition, if a lower frequency such as 30 Hz, transformer efficiency is low, it will be detrimental to the AC transformer and transmission.
In case of the same voltage, what is the difference between 50Hz and 60Hz on the transmission power and the rectification efficiency?
Do not use 100Hz or 120Hz is because the frequency is too high, on the one hand, transportation will be difficult; on the other hand, the generator and the motor speed are too high. If you need to put 50Hz into 60Hz production line, AC motor speed decreases but temperature increases, long time working will cause inevitably damage.
If you want to convert 50Hz power supply directly to 60Hz power line, the main consideration of the electromagnetic properties of electromagnetic devices, such as motors, transformers, followed by power frequency related to the sampling signal. For the former, research methods can be found in the electromagnetic expression of these two devices, respectively input 50Hz and 60Hz power supply, you can find some issues.
For asynchronous motor, when supplying 50Hz power to 60Hz motors, speed reduction is affirmative, the voltage should be decreased by 1/6 of the motor nameplate. At this time, the motor can be long-running, and the torque, constant current, power reduced 1/6. If the voltage is not reduced, it will cause the motor magnetic saturation, no-load current and no-load loss increases a lot.
For inductors, the inductance decreases 1/6. For 60Hz dedicated contactors, convert into 50Hz, it will be easily mistaken for tripping. But this is generally working for both 50 Hz and 60 Hz.
Conversion between 50Hz and 60Hz can be achieved by frequency converter. There are many mature frequency converters on market, i.e. GoHz.
Single phase frequency converter main circuit has a frequency conversion circuit for AC-DC-AC, mainly by rectifying, filtering and converting components.
Rectify part apply single phase rectifier bridge rectifier module, realize AC/DC converting;
Filtering part using filter capacitor to stabilize the DC voltage;
Converting part applied PWM system to achieve DC/AC conversion.
Frequency converter control circuit is used to adjust the frequency and amplitude of the output signal of the power supply system, in order to achieve variable voltage and variable frequency. To ensure safe and reliable of the system, generally it provides over-voltage protection circuit detection, isolation optocoupler driver circuit, and auxiliary power conversion circuit etc.
If only to supply the small power load instrument, you can try the following ways:
First, after the rectifier regulator 220V AC into 110V DC, by means of a switch (MOS, IGBT high voltage) series with the load, and then 60Hz signal driving the switch, you can approximate the actual power supply.
Second, the sampling frequency meter partially broken, external 60Hz signal is supplied, because some meter chip itself without base oscillation circuit, instead of using the mains frequency, such circuits can be allowed to work through the applied frequency compatibility.