Understanding how power (electricity) affects computers is a must for every tech. Power might sound easy to understand: a cable that you plug into your computer. But there is far more to it than meets the eye.
In this post, I want to show you that power is more than just a tool to turn on and off your device.
Problems with power can create system instability, crashes, and data loss. In order to solve computer issues, it is important to know the basic principles of electricity and to know the many variations of PC power supplies.
Many techs are in the “just plug it in” camp and never fully understand how power can affect workstations. This can lead to wrong decisions/investments that companies make, based on incorrect troubleshooting by techs in case an error appears on a system.
Electricity basics
Electricity is a flow of negatively charged particles. These particles are called electrons. Particles (electrons) move through matter. You can compare the flow of electricity with the flow of water through pipes.
Electricity companies gather or generate electricity and push this electricity to your house or company. This is done by putting electricity under pressure to move it: exactly the same as how water is transported through its pipes to flow through your water tap.
Just like water (that is in pipes), electricity has also a transportation utility: wires that are waiting for someone to put a plug of a device in the wall socket. After that, the electricity flows at a (more or less) constant rate through the plug and cable into your device. This way the device receives its power.
The pressure of the electrons in the wire is called voltage. Voltage is measured in units, called volts (V). The amount of electrons that move past a certain point on a wire is called the current (also called amperage). This is measured in units called amperes (amps or A).
In order for your device to operate properly, you need the right wattage (watts or W) that this device needs. The correlation between these three terms is simple math: Voltage (V) x Amperes (A) = Wattage (W).
All wires have a slight resistance to the flow of electrons. You can compare this with the flow of water through pipes as well: water pipes also have a slight amount of friction that resists the flow of water. The resistance to the flow of electrons is measured in ohms (Ω).
If you push too many electrons through, the wire will overheat and break. To make sure that this will not happen, all electrical wires have an amperage rating, such as 20 amps. If you want to push 30 amps through a 20-amp wire, the wire will break and the electrons will seek a way to return to the ground. Worst case: through the people that are in direct contact with a person that is directly connected with the line. This is the reason why circuit breakers and ground wires are a must in an electrical network: they provide basic protection from accidental overflow.
Circuit breakers are heat-sensitive or electromagnetically operated electrical switches, rated for a specific amperage. If too much amperage is pushed through, the wiring inside detects the increase in heat or current and automatically opens, stopping the flow of electricity before the wiring overheats and breaks. You can reset the circuit breaker to reestablish the circuit, and electricity flow once more through the wires.
A ground wire provides a path of least resistance for electrons to flow back to the ground in case of an accidental overflow. Important to know: an electrical outlet must have a ground wire to be suitable for a workstation to use. Without a ground wire, the workstation won’t work.
Circuit wires and ground wires are a must in incident prevention related to electricity. Not only at home but also in your company. Especially OT environments with a lot of electrical devices can create dangerous situations if the flow of electricity is not properly managed and prevention measurements like installing circuit wires and ground wires are not (fully) taken.
AC/DC
Electricity has two flavors:
- Alternating current (AC): with AC, the flow of electrons alternates direction back and forth in a circuit.
- Direct current (DC): with DC, electrons flow in one direction around a continuous circuit
Most electronic devices use DC power but all power companies supply AC power. This is done because AC travels over a long distance in a much more efficient way than DC. On the other hand, AC is not stable and electrical devices need a stable flow. This is the reason why all devices use DC:
So how do you make AC power that flows out of your socket compatible with devices (that all use DC power)? This is done by a conversion process. The conversion takes place inside the device itself by the power supply inside the device. The power supply converts high-voltage AC power from your wall socket into low-voltage DC. In the case of a computer, the first step is to get and maintain a good supply of AC power. Secondly, you need a power supply to convert AC into the proper voltage and amperage of DC power for the motherboard of your computer and peripherals. The third step is to provide the system with sufficient cooling because electricity has a byproduct: heat. The more power your system requires, the more heat is generated as a byproduct.
AC supply and computers
Desktop Computers use a special box, the power supply unit (PSU). The PSU converts electricity from your wall socket (AC) into computer power.
There is a catch in AC supply: the United States has standard AC flowing through the lines between 110 and 120V while most of the rest of the world use 220-240V. This is the reason why power supplies have dual-voltage options. This way they are compatible with either standard. However, pay attention that you don’t switch the button to 120V while using an AC outside of the United States with 220-240V: this creates very dangerous situations. The other way around is not much of a problem because you only use half of the AC power. However, in the rest of the world, it leads to a power overload so watch that switch and check the power.
Computers use the IEC-320 plug that has three holes. These holes are called hot, neutral, and ground:
The hot wire carries electrical voltage (like a pipe that delivers the water), the neutral wire carries no voltage but acts as a water drain, completing the circuit by returning electricity to the local source which is in most cases a breaker panel. The ground wire makes it possible for excess electricity to return safely to the ground (for instance in case of a short-circuit condition).
In addition to desktop computers, there are many more computing devices (including laptops). These devices use an AC adapter instead of an internal power supply. An AC adapter converts AC current to DC. It works the same as a power supply. AC adapters are rarely interchangeable so if you plug an AC adapter from the laptop of someone else into your own laptop there is a big chance it is not going to work. In order to get it to work, you need to check the adapter for three things that need to match: voltage, amperage, and polarity. If voltage or amperage output is too low, the device won’t run. If the polarity is reversed, it won’t work either: it’s like putting a battery backward into a flashlight. There is an extra catch: if voltage or amperage (especially voltage) is too high, you might fry your device. So always check the voltage, amperage, and polarity of a replacement AC adapter before plugging it into a device.
Electricity surges and preventing this
Because the power company delivers AC, Voltage from the power company drops well below (sag) and shoots far above (surge or spike) the standard of 220V. Large sags in electricity are also called brownouts. When power cuts out completely you have a blackout.
When different devices are connected to the same power group, a peak can appear as well in case a specific device suddenly eats up a lot of power. This can happen when initial power is suddenly required, for instance when you suddenly switch from working in a text editor to your brand new 3D shooting game that needs a lot of power from your graphical card.
To handle spikes and sags in the supply of AC you can use surge suppressors and uninterruptible power supplies.
Surge suppressors
Sags are not as dangerous as surges or spikes. A strong sag only shuts off or reboots your device. Surges are different though: they can seriously harm your device, destroying components in your device. This is why every device should use a surge suppressor that absorbs the extra voltage from a surge to protect the device:
Make sure to check the joules rating before buying a new suppressor. A joule is a unit of electrical energy. How much energy a surge suppressor can handle before it fails, is described in joules. Most governmental institutions agree that the suppressor should at least have a minimum of 2.000 joules. The more joules, the better the protection. There are suppressors out there of 3.500 joules and more.
No surge suppressor works forever so make sure that your surge suppressor has a test/reset button so that you know for sure that your suppressor is working as intended. If not: replace the suppressor immediately otherwise, it’s just an extension cord.
Uninterruptible Power Supply (UPS)
A UPS protects a device and more importantly: the data in the event of a power sag or power outage. A UPS has a huge battery that provides AC power to your computer, regardless of the power coming from the AC outlet. All UPS’s are measured in both watts and in volt-amps (VA). Volt-amps are the amount of power that the UPS can supply if the device would take power from the UPS in a perfect way. This is never the case: UPS makers don’t know what devices a customer plans to plug in the UPS so the exact watts can’t be told. Different devices have different efficiencies which is the reason why UPS makers go by what they can offer (VAs) instead of what a device will take (watts). The watts value is a guess, and it is never higher than the VAs: VA rating is always higher than watt rating.
In order to decide what UPS is suitable, add up the total wattage of every component in your device and buy a UPS with a higher wattage. To support you in determining the total wattage, you can also go to a major surge suppressor/UPS makers’ Web site and use their power calculator tool. We use APC ourselves in our company and the APC website has a great online calculator that shows us the true wattage we need. It also teaches us about new things that happen around power at the same time.
Also, note that the UPS is just a huge battery with a limited amount of power. This means you have to figure out how long your want the UPS to run when you lose power.
There are two main types of UPS:
- Online: where devices are constantly powered through a UPS’s battery
- Standby: where devices connected to the UPS receive battery power only when the AC goes below ca. 190 – 210 V.
In addition to this, there is also a hybrid UPS that is called line-interactive. This is similar to a standby UPS but has special circuitry to handle moderate AC sags and surges without the need to switch to battery power.
Final Thoughts
This post was inspired based on a situation that occurred not long ago in our own OT (Operational Technology) environment. One of the AOI (All-in-One) workstations in this OT environment reported a hard disk error now and then. At first, we thought that there might be something wrong with the hard disk but after some out-of-the-box thinking, we had a different (far more uncommon) diagnosis: the issue was power-related. Because an electrical welding device was also plugged into the same socket group as the workstation, the workstation sometimes ran into a hard disk error mode after welding started. This happened because the welding device created an electricity peak now and then, taking up all electricity which meant that all other devices directly linked with the same socket group received less electricity: serious sagging happened. Receiving less electricity, affected the workstation because the hard drive did not receive a constant flow of stable power. The solution was simple: plugging in a surge suppressor. This prevented an unnecessary (and unjustified) guarantee claim with the manufacturer. Sometimes the rabbit hole is a bit deeper than you think and power is not always the first thing you think of.
And finally: no surge suppressor can beat the ultimate surge though: the electrical discharge of a lightning strike. Always unplug all your electronics during electrical storms!
Feel free to contact me if you have any questions or if you have any additional advice/tips on this subject. If you want to keep in the loop when I upload a new post, don’t forget to subscribe to receive a notification by e-mail.
