Although standard power supply methods are normally sufficient for handling most commercial or industrial applications, electrical disturbances can sometimes harm the performance of sensitive equipment or interrupt vital operations. Interferences in power supply can be particularly harmful in computerized systems, which require stable, continuous electrical power to reduce the risk of data loss and distortion of control signals. For these reasons, electronic power supplies manufacturers offer protection from certain unwanted conditions. In this sense, uninterruptible power supply (UPS) units may provide significant benefits to performance stability and cost-efficiency by decreasing industrial system downtime, lowering the rate of equipment malfunction, and reducing the potential for process interruptions. Total power outage from an electrical source is a rarity under most conditions, but even mild power fluctuations and brief breaks in supply current can prove harmful, especially if they occur during a critical processing stage.

Disruptive electrical interference, such as surges, can result from a variety of different causes, including power switching operations, the presence of other electrical equipment in the vicinity of the operating system, and natural phenomena such as lightning and thunderstorms. Understanding the various kinds of electrical interference and their effects on power supply systems can be helpful in developing strategies to safeguard vulnerable industrial processes. One of the most common and unpredictable sources of sudden power spikes is atmospheric lightning, which can severely affect an electricity supply network. A lightning strike into a power line, overhead line, or cable can generate a high-voltage spike that disrupts current transmission. Similarly, switching operations, particularly those in the vicinity of other sensitive electrical equipment, can also produce spikes. Switchgear that operates on heavy current and certain fuses may yield transient spikes even under standard performance conditions.

Major electrical system faults can produce high-amplitude transient spikes ranging up to hundreds or thousands of volts, although they are of brief duration and usually have a short rise time. small ac wall unitOther common sources for spikes in electrical power supply include: The switch starting and stopping of induction motors, like the ones found in driving pumps and fans, can lead to comparable spiking effects. used air conditioner units for saleRandom electrical spikes usually have amplitudes not in excess of 800 volts and with rise times as short as several nanoseconds. window ac unit not cooling enoughDips and Surges Unintended surges in an electrical power supply are most often the result of switching off large electric loads, while electrical dips occur from switching on.

The most important factor in both surges and dips is the size of the load being switched relative to the transformer rating at the power supply source. The duration of a surge or dip can vary from a single half-cycle of the supply waveform to several half-cycles, while the variation from the standard voltage often exceeds 6 percent above or below the optimal range. Large fluctuations in a high-voltage supply network can be caused by system faults or load switching in an industrial power plant, and the frequency and scale of voltage disturbances beyond an initial power supply source depends on the quality of the local electrical distribution network. In some industrial processes, the potential for surges and dips can be a significant concern. Applications that involve high power loads, such as arc furnaces used in steel working or reversing mill motor drives, can produce severe voltage fluctuations. Through transmission along the supply network, these fluctuations can cause performance interference or flickering.

A flicker is a more minor disturbance, usually only a few hertz in strength and characterized by a voltage amplitude with a relatively small deviation from the standard range. Harmonics are another common cause of electrical interference among power supplies. In most alternating current power systems, voltage variations occur along a sine wave frequency, but a non-linear electric load can generate a different frequency for the current waveform. These harmonics changes may cause an increase in system current that can lead to excess heating and component malfunction. Typical sources for harmonics include solid-state semiconductors, current rectifiers, discharge lamps, and variable speed and induction motors. While the harmonic variation will usually be no greater than 2 to 5 percent on most distribution systems, in some cases a higher degree of harmonic fluctuation may occur. The Department of Energy’s provides more information on harmonics measurements.Find the right power adapter and cord for your Mac notebook

Learn which power adapter, cord, and plug comes with your Mac notebook. General informationPower adapters for Apple notebooks are available in 29W, 45W, 60W, and 85W varieties. You should use the appropriate wattage power adapter for your Apple notebook. You can use a compatible higher wattage adapter without issue, but it won't make your computer charge faster or operate differently. Lower wattage adapters will not provide enough power. MagSafe power adapters have three pieces: Connector and adapter, AC cord, and the AC plug or "duckhead." The Apple 29W USB-C power adapter and USB-C Charge Cable is made of two pieces: a charging cable and an adapter with a removable duckhead. Note that AC cords and plugs might be different than the examples above depending on your location. Power adaptersThe tables below show the style of adapter that came with each model MacBook, MacBook Pro, and MacBook Air. If you're not sure which model Mac you have, use these articles.

How to identify MacBook models How to identify MacBook Pro models How to identify your MacBook Air Computers that use the Apple 29W USB-C Power Adapter and USB-C Charge Cable MacBook (Retina, 12-inch, Early 2015) Apple 29W USB-C power adapter and USB-C Charge Cable Computers that use the 85W MagSafe 2 Adapter MacBook Pro (Retina, 15 inch, Mid 2015) MacBook Pro (Retina, 15-inch, Mid 2014) MacBook Pro (Retina, 15-inch, Late 2013) Macbook Pro (Retina, 15-inch, Early 2013) MacBook Pro (Retina, Mid 2012) 85W MagSafe power adapter with MagSafe 2 style connector Computers that use the 60W MagSafe 2 Adapter MacBook Pro (Retina, 13-inch, Early 2015) MacBook Pro (Retina, 13-inch, Mid 2014) MacBook Pro (Retina, 13-inch, Late 2013) MacBook Pro (Retina, 13-inch, Early 2013) MacBook Pro (Retina, 13-inch, Late 2012) 60W MagSafe power adapter with MagSafe 2 style connector Computers that use the 45W MagSafe 2 Adapter

MacBook Air (11-inch, Early 2015) MacBook Air (13-inch, Early 2015) MacBook Air (11-inch, Early 2014) MacBook Air (13-inch, Early 2014) MacBook Air (11-inch, Mid 2013) MacBook Air (13-inch, Mid 2013) MacBook Air (11-inch, Mid 2012) MacBook Air (13-inch, Mid 2012) 45W MagSafe power adapter with MagSafe 2 style connector About the MagSafe to MagSafe 2 ConverterIf you have an older MagSafe adapter, you can still use it with newer Mac computers that have MagSafe 2 ports. To do this you just need a MagSafe to MagSafe 2 Converter (shown below). MagSafe "L" and "T" shaped adapters Computers that use the 60W MagSafe Adapter MacBook Pro (13-inch, Mid 2009) MacBook Pro (15-inch, 2.53GHz, Mid 2009) MacBook (13-inch, Mid 2009) MacBook (13-inch, Early 2009) MacBook (13-inch, Aluminum, Late 2008) MacBook (13-inch, Late 2008) MacBook (13-inch, Early 2008) MacBook (13-inch, Late 2007) MacBook (13-inch, Mid 2007)

MacBook (13-inch, Late 2006) 60W MagSafe power adapter with "T" style connector MacBook Pro (13-inch, Mid 2012) MacBook Pro (13-inch, Late 2011) MacBook Pro (13-inch, Early 2011) MacBook Pro (13-inch, Mid 2010) MacBook (13-inch, Mid 2010) MacBook (13-inch, Late 2009) 60W MagSafe power adapter with "L" style connector Computers that use the 85W MagSafe Adapter MacBook Pro (15-inch Mid 2009) MacBook Pro (17-inch Mid 2009) MacBook Pro (17-inch Early 2009) MacBook Pro (15-inch Late 2008) MacBook Pro (17-inch Late 2008) MacBook Pro (15-inch Early 2008) MacBook Pro (17-inch Early 2008) MacBook Pro (15-inch 2.4/2.2GHz) MacBook Pro (17-inch 2.4GHz) MacBook Pro (15-inch Core 2 Duo) MacBook Pro (17-inch Core 2 Duo) MacBook Pro (15-inch Glossy) 85W MagSafe power adapter with "T" style connector MacBook Pro (15-inch, Mid 2012) MacBook Pro (15-inch, Late 2011) MacBook Pro (17-inch, Late 2011)

MacBook Pro (15-inch, Early 2011) MacBook Pro (17-inch, Early 2011) MacBook Pro (15-inch, Mid 2010) MacBook Pro (17-inch, Mid 2010) 85W MagSafe power adapter with "L" style connector Computers that use the 45W MagSafe Adapter MacBook Air (Mid 2009) MacBook Air (Late 2008) Note: Adapters that shipped with the MacBook Air (Original), MacBook Air (Late 2008), and MacBook Air (Mid 2009) are not recommended for use with MacBook Air (Late 2010) models. When possible, use your computer's original adapter or a newer adapter. 45W MagSafe power adapter with "L" style connector MacBook Air (13-inch, Mid 2011) MacBook Air (11-inch, Mid 2011) MacBook Air (13-inch, Late 2010) MacBook Air (11-inch, Late 2010) Learn moreYou can get extra or replacement adapters with AC cord and plug at the Apple Online Store (links below), an Apple Reseller, or an Apple Store. Apple 60W MagSafe Power Adapter (for MacBook and 13-inch MacBook Pro)