A reliable power source is an important part of any technology infrastructure. In this video, you’ll learn about the basics of power and how to protect against power interruptions using a UPS and power distribution unit.
In this video, we’re going to talk about power. And an important thing to remember is that you should never put yourself in a position where you will be able to in some way come in contact with any type of voltage. You want to be sure that when you’re working with a device, that you are always disconnecting from the power source before ever putting your hands or any part of you near that particular component.
Even when you disconnect from the power source, you should also keep in mind that some devices will store a charge in capacitors. Older CRT monitors, laser printers, and other devices can easily shock you even when they’re not connected to a power source.
Your goal should never be to connect any part of your body to anything that could potentially be energized. For example, you should never connect yourself to the ground wire of an electrical system or anything else that might have some type of voltage go across it. If you respect electricity, you will have no problems keeping yourself and others around you safe as you’re working on these devices.
When you start looking into the electrical specifications and the design of electrical systems, you’ll see a lot of different terms being used. One of those is an ampere. We often refer to this as an amp, and it’s often abbreviated with a capital letter A. This value measures the rate of electrons that are moving past a particular point in a single second.
You’ll often hear electricity compared to a water hose, where electricity flowing through a wire is very similar to water that may be flowing through a water hose. The amount of water that you can fit through a hose will depend on the diameter of that hose, and the diameter would be the number of amps.
We also measure electricity in terms of voltage. This is often abbreviated as volt or the capital letter V. This is describing a pressure of electricity flowing through a particular wire. If we go back to our hose analogy, as we are turning the water on, we are increasing the amount of pressure of that water through the hose. And as we increase the pressure, we are increasing the voltage. For example, you’ll often see electrical systems described as a 120 volt system or a 240 volt system.
And if you need to describe how much power is being used, we would describe that as a number of watts. You’ll often see this abbreviated with a capital W. We can calculate watts by multiplying the number of volts times the number of amps. For example, if you’re connected to a 120 volt power source and you have a device that is using 0.5 amps, you are using a total of 60 watts.
The type of power that we usually get from our wall outlets is Alternating Current, or AC. AC power is relatively easy to distribute over long distances, so it is perfect to use for bringing into a home or an office. You’ll often see Alternating Current abbreviated as AC, and it’s often represented as a wavy line. This wavy line demonstrates the directional change of this power as it’s moving through the wire.
That up-and-down frequency of that wave is different depending on where you happen to live. If you’re in the US or Canada, we commonly see 110 to 120 volts of alternating current, and it’s usually running at a frequency of 60 hertz, or 60 cycles per second. If you’re in Europe, it’s common to see 220 to 240 volts of AC current, and its frequency is 50 hertz.
Our electrical components often use DC power to operate. This is Direct Current, where all of the current is moving in a single direction with a constant amount of voltage. This is often abbreviated with a DC. And the symbol for direct current is this solid line on top with the multiple lines across the bottom.
This is why when we look on the back of our routers, our switches, and our other devices, we often see that we’re plugging into a wall outlet with this alternating current, and we are converting that alternating current to direct current using the power supplies that are in those devices. This conversion may be occurring in power supplies built into the device, or it may be in the power cord that you’re using to connect that device.
And obviously, as an information technology, professional, power is one of the most important components we have. None of these systems would work without this power source. So it’s important to consider how our switches, our routers, and our other devices will continue to operate even if there is an interruption of that power.
One way to protect yourself against a power outage is to use a UPS. This is an Uninterruptible Power Supply. This is usually a device that is connected to our power source. And inside of this device are a number of batteries that provide us with additional power if we lose that main power connection. This can also help if the voltage on our line tends to drop a bit. We refer to that as a brownout. And if the voltage tends to spike or go much higher, we refer to that as a surge. The UPS will even out that particular surge or brownout and provide us with the power we need to remain up and running.
There are a number of different types of uninterruptible power supplies. One of the least expensive are the offline or standby UPS, which is simply waiting for the power to go out before it kicks in. As you can imagine, there’s a small amount of time where there would be no power available to your systems. And often with switches and routers, that small gap of time is enough to cause that device to reboot.
One step up from that is the line-interactive UPS. If you happen to have brownouts and your voltage begins to drop, the line-interactive UPS will begin to increase the amount of power provided to be able to compensate for that drop. But many data centers prefer to run an online or double-conversion UPS where you are always running from battery power and the batteries are constantly being refreshed by the power source. If you lose the power source, it has no effect on the systems that are connected to the UPS because they’ve always been running from that primary battery power.
There are many different types of UPS’s with many types of features. There are some that can automatically shut down your system if the batteries happen to become very low. Some of them have a higher battery capacity than others. The number of outlets on the back of the UPS can vary, and some of them have additional interfaces to plug in phone lines or cable modem connections.
Another useful power component is a PDU. This is a Power Distribution Unit and although it looks like a normal surge suppressor, these are actually relatively intelligent devices that allow us to remotely connect to the device, manage each of those interfaces, and even allow you to power off and power on a device from a remote location.
You can see this one is a rack mountable unit. And we would put that in our rack and connect our routers and switches to these interfaces. There’s also an ethernet connection. We would assign an IP address to this device. Inside is a web server. And that allows us to connect and manage this device from wherever we happen to be.