Electrical appliances are usually very sensitive to voltage fluctuations. And as you know, voltage fluctuation in city electricity is almost a daily thing. Factories producing electrical appliances usually use a power supply to solve this problem.
Usually, the work of a power supply in such devices is to prevent destructive power fluctuations for the device. But when the electricity in the city is cut off, the power source does not work.
If you use your computer a lot, you have probably experienced a power outage while working with your computer, and if you are a lucky person, your computer may still be working properly. Of course, in most cases, at least the computer motherboard is damaged. If the CPU is not burned, it must be said that you are still a relatively lucky person.
Nowadays, with motherboards that are not very expensive, you can use various inexpensive methods to protect the computer motherboard from power supply (city electricity) problems. But no method like using UPS and Uninterruptible Power Supplies or an uninterruptible power supply can protect your expensive equipment from power problems. When you have an expensive server or computer, the importance of having a UPS increases.
UPS has special circuits to filter the unwanted fluctuations of the input power and control its voltage. And to solve the problem of power outage or excessive voltage drop (voltage drop is harmful for many equipments or causes them to stop working temporarily), it uses a battery, which is called backup power supply.
Types of UPS
In the general concept, there are two types and forms: online (UPS Online) – offline (Line Interactive UPS) and each of these two can be sinusoidal, quasi-sinusoidal, square, etc.
Online UPS
First, it converts the city electricity or the input from AC to DC, and then it converts DC to AC, and in this process, the output is completely isolated from the input, and this is the best case of a UPS. But the inverter is always in the circuit and performs the conversion operation. In these models, the switching time between battery usage (back up mode) and city electricity usage (normal mode) is zero milliseconds.
Offline UPS
In offline models, the inverter or converter is used only when the input power is cut off or out of a certain range, in other words, the UPS bypasses the city power when connected to the output and only performs the stabilizer operation. And the transfer time is usually between 1 and 3 milliseconds.
*** Note: Computer systems do not notice a power cut for less than 4 milliseconds.
Simulated Sin Wave
Pseudo-sinusoidal systems This waveform is created in pseudo-sinusoidal UPSs during a power outage, and the DC waveform is a step that the UPS tries to simulate the city’s electrical waveform.
But how to choose a good UPS?
In answer to this question, it must be said that it depends on your ability to pay and for what purpose you use UPS. The energy consumption of what you are protecting is another factor that plays an important role in purchasing a UPS. The unit by which the capacity of the UPS or the amount of energy it gives you is expressed in ampere-hours. For example, a 50 amp-hour UPS can power your device with 2 amps for 25 hours or 5 amps for 10 hours. Note that the amount of current consumed is determined by the consumption of the device, so the feeding time for a specific UPS depends on the consumption of your device.
Obviously, if the critical time you need a power source is short, you can use a UPS with less ampere-hours and therefore cheaper. Of course, there is a limitation in this field, which is that the rated current of your UPS must be greater than the total power of your devices (in amps). 400w is calculated and at the end add 200w to the total number to be sure.)
Another point that you should pay attention to is that you should never use an electrical protector (such as a refrigerator or computer protector) at the output of a UPS, you should not use these protectors for the same device at the same time because it will damage the device and even Your safety opinion can also be dangerous.
Usually, the price of UPS has a wide range so that even those with less financial ability can buy it. Of course, it is natural that a higher price will bring you more quality and facilities.
