Electrical generator

In areas where the power frequency is 60 Hz (United States), generators rotate at 1800 rpm or another even multiple of 60. Fibre channel (FC) interfaces are left to discussions of server drives. This produces power at 50 Hz, which is the frequency used in the UK. However, as of 2005, performance of SATA and PATA disks is comparable. These diesel engines are run in the UK on red diesel and rotate at 1500 rpm. In order for EIDE's performance to increase (while keeping the cost of the associated electronics low), it was realized that the only way to do this was to move from "parallel" interfaces to "serial" interfaces, the result of which is the SATA interface. Stationary generators used in the US are used in size up to 2800 kW. The increase in SCSI performance came at a price — its interfaces were more expensive.

It's powered by a 6.7 litre turbocharged Perkins Phaser 1000 Series engine, and consumes approximately 27 litres of fuel an hour, on a 400 litre tank. While EIDE was introduced, though, SCSI manufacturers continued to improve SCSI's performance. The mid-size stationary engine-generator pictured here is a 100 kVA set which produces 415 V at around 100 A per phase. These drives were known as EIDE. Trailer-mounted generators can be towed to disaster areas where grid power has been temporarily disrupted. IDE manufacturers attempted to close this speed gap by introducing Logical Block Addressing (LBA). Small and medium generators are especially popular in third world countries to supplement grid power, which is often unreliable. IDE drives were slower because they did not have as big a cache as the SCSI drives, and they could not write directly to RAM.

Hospitals, communications service installations, sewerage pumping stations and many other important facilities are equipped with standby power generators. Eventually, IDE manufacturers wanted the speed of IDE to approach the speed of SCSI drives. Standby power generators are permanently installed and kept ready to supply power to critical loads during temporary interruptions of the utility power supply. This advance was known as "Integrated Drive Electronics" or IDE. for traveling carnivals. When the price of electronics dropped (and because of a demand by consumers) the electronics that had been stored on the controller card was moved to the disk drive itself. Trailer-mounted generators supply power for lighting, amusement rides etc. SCSI (originally named SASI for Shugart (sic) Associates) or Small Computer System Interface was an early competitor with ESDI.

Small generators are sometimes used to supply power tools at construction sites. It allowed for faster communication between the PC and the disk. Engine-generators are often used to supply electrical power in places where utility power is not available and in situations where power is needed only temporarily. ESDI was an interface developed by Maxtor. The smaller units tend to use gasoline (petrol) as a fuel, and the larger ones have various fuel types, including diesel, natural gas and propane (liquid or gas). Most RLL drives also needed to be "compatible" with the controllers that communicated with them. These include small, hand-portable units that can supply several hundred watts of power, hand-cart mounted units, as pictured above, that can supply several thousand watts and stationary or trailer-mounted units that can supply over a million watts. RLL (Run Length Limited) was a way of encoding bits onto the platters that allowed for better density.

Engine-generators are available in a wide range of power ratings. MFM drives required that the electronics on the "controller" be compatible with the electronics on the drive — disks and controllers had to be compatible. Both single-phase and three-phase models are available. As far as PC history is concerned, the major drive families have been MFM, RLL, ESDI, SCSI, IDE and EIDE, and now SATA. The generator voltage (volts), frequency (Hz) and power (watts) ratings are selected to suit the load that will be connected. As of early 2005, the "smallest" desktop hard disk in production has a capacity of 40 gigabytes, while the largest-capacity internal drives are a half terabyte (500 gigabytes), with external drives at or exceeding one terabyte. Engine-generators produce alternating current power that is used as a substitute for the power that might otherwise be purchased from a utility power station. In the latter half of the 1990s, hard drives with capacities of 1 gigabyte and greater became available.

Standby power generating units often include an automatic starting system and a transfer switch to disconnect the load from the utility power source and connect it to the generator. With early personal computers, a drive with a 20 megabyte capacity was considered large. Many units are equipped with a battery and electric starter. The capacity of hard drives has grown exponentially over time. In addition to the engine and generator, engine-generators generally include a fuel tank, an engine speed regulator and a generator voltage regulator. The appearance in the late 1990s of high-speed external interfaces such as USB and FireWire has made external disk systems popular among regular users once again, especially for users who move large amounts of data between two or more locations, and most hard disk makers now make their disks available in external cases. In many contexts, the engine is taken for granted and the combined unit is simply called a generator. External SCSI drives were also popular with older microcomputers such as the Apple II series and the Commodore 64, and were also used extensively in servers, a usage which is still popular today.

This combination is also called an engine-generator set or a genset. Every Mac made between 1986 and 1998 has a SCSI port on the back, making external expansion easy; also, "toaster" Macs did not have easily accessible hard drive bays (or, in the case of the Mac Plus, any hard drive bay at all), so on those models, external SCSI disks were the only reasonable option. An engine-generator is the combination of an electrical generator and an engine mounted together to form a single piece of equipment. While internal drives became the system of choice on PCs, external hard drives remained popular for much longer on the Apple Macintosh and other platforms. A small propellor, wind turbine or impeller is connected to a low-power alternator and rectifier to supply currents of up to 10 A at typical cruising speeds. Hard disk makers started marketing to end users as well as OEMs, and by the mid-1990s, hard disks had become available on retail store shelves. Sailing yachts may use a water or wind powered generator to trickle-charge the batteries. The IBM PC/XT had an internal hard disk, however, and this started a trend toward buying "bare" drives (often by mail order) and installing them directly into a system.

Aircraft have also switched from DC generators to alternators; these are typically powered by a takeoff from an engine. Most microcomputer hard disk drives in the early 1980s were not sold under their manufacturer's names, but by OEMs as part of larger peripherals (such as the Corvus Disk System and the Apple ProFile). A battery would be required in order to use a controllable electromagnetic field instead, and this is unacceptable due to its weight and bulk. In fact, in its factory configuration the original IBM PC (IBM 5150) was not equipped with a hard drive. Nevertheless, the maximum efficiency is only around 60% for the best generators - 40% is more typical - due to the use of permanent magnets. Because of this, hard disks were not commonly used with microcomputers until after 1980, when Seagate Technology introduced the ST-506, the first 5.25-inch hard drive, with a capacity of 5 megabytes. Being powered by the rider, efficiency is at a premium, so these may incorporate rare-earth magnets and be designed and manufactured with great precision. Before the early 1980s, most hard disks had 8-inch (20 cm) or 14-inch (35 cm) platters, required an equipment rack or a large amount of floor space (especially the large removable-media drives, which were often referred to as "washing machines"), and in many cases needed high-amperage or even three-phase power hookups due to the large motors they used.

These tend to be 0.5 A permanent-magnet alternators, supplying 3-6 W at 6 V or 12 V. For many years, hard disks were large, cumbersome devices, more suited to use in the protected environment of a data center or large office than in a harsh industrial environment (due to their delicacy), or small office or home (due to their size and power consumption). Some of the smallest generators commonly found are used to power bicycle lights. Project head designer/lead designer Kenneth Haughton named it after the Winchester 30-30 rifle after the developers called it the "30-30" because of its two 30 MB spindles. Vehicle alternators do not use permanent magnets; they can achieve efficiencies of up to 90% over a wide speed range by control of the field voltage. Almost all modern disk drives now use this technology, and the term "Winchester" became a common description for all hard disks, though generally falling out of use during the 1990s. Commercial vehicles are more likely to use 24 V to give sufficient torque at the starter motor to turn over a large diesel engine. In 1973, IBM introduced the 3340 "Winchester" disk system the first to use a sealed head/disk assembly (HDA).

Rated output will typically be in the range 50-100 A at 12 V, depending on the forecast electrical load within the vehicle - some cars now have electrically powered superchargers and airconditioning, which places a high load on the electrical system. The first disk drive to use removable media was the IBM 1311 drive, which used the IBM 1316 disk pack to store two million characters. These power the electrical systems on the vehicle and recharge the battery after starting. The IBM 1301 Disk Storage Unit, announced in 1961, introduced the usage of a separate head for each data surface. These were not particularly reliable or efficient and have now been replaced by alternators with inbuilt rectifier circuits. A single head was used for access to all the platters, making the average access time very slow. Early motor vehicles tended to use DC generators with regulators. This drive had fifty 24 inch platters, with a total capacity of five million characters.

For this reason, practical generators are not usually designed to operate at maximum power output, but at a lower power output where efficiency is greater. The first hard disk drive was the IBM 350 Disk File, invented by Reynold Johnson and introduced in 1955 with the IBM 305 computer. However, under this condition the power transfer efficiency is only 50%, which means that half the power generated is wasted as heat inside the generator. In 2005 the first cellular telephones to include hard disk drives were introduced by Samsung and Nokia. This theorem states that the maximum power can be obtained from the generator by making the resistance of the load equal to that of the generator. Applications for hard disk drives expanded to include personal video recorders, digital audio players, digital organizers and digital cameras. The maximum power theorem applies to generators as it does to any source of electrical energy. Hard disks are also found in network attached storage (NAS) devices, but for large volumes of data are most efficiently used in a storage area network (SAN).

Note 2: If the generator is an AC type (distinctly not a dynamo), use an AC voltmeter for the voltage measurements. From the original use of a hard drive in a single computer, techniques for guarding against hard disk failure were developed such as the redundant array of independent disks (RAID). For rough calculations, you can omit the measurement of R_GAC and assume that R_GAC and R_GDC are equal. However, for large (several GiB) filesystems, this data rarely occupies more than several MiB, and therefore cannot possibly account for the apparent "loss" of tens of GBs. The above procedure allows you to measure both values. Another side point is that many people mistakenly attribute the discrepancy in reported and advertised capacities to reserved space used for file system and partition accounting information. Note 1: The AC internal resistance of the generator when running is generally slightly higher than its DC resistance when idle. KiB, MiB, GiB) since their definitions are unambiguous.

To determine the generator's V_G and R_G parameters, follow this procedure: -. For this very reason, many utilities that report capacity have begun to use the aforementioned IEC standard binary prefixes (e.g. The equivalent circuit of a generator and load is shown in the diagram to the right. Since utilities provided by the operating system probably define a gigabyte as 2³⁰, or 1073741824, bytes, the reported capacity of the drive will be closer to 186.26 GB (actually, GiB), a difference of well over 7 percent. The generator rotor is turned by a device termed a prime mover, often a Diesel engine, steam turbine, water turbine or gas turbine coupled to the rotor shaft. This uses the proper SI definition of "giga," 10⁹ and can be considered as an approximation of a gibibyte. Also, all common types of electric motors could work as generators. For example, a drive advertised as 200 GB can be expected to store close to 200 x 10⁹, or 200 billion, bytes.

The construction of a dynamo is similar to that of an electric motor, and all common types of dynamos could work as motors. This trend became habit and continued to be applied to the prefixes "mega," "giga," and even "tera." Obviously the discrepancy becomes much more noticeable in reported capacities in the multiple gigabyte range, and users will often notice that the volume capacity reported by their OS is significantly less than that advertised by the hard drive manufacturer. Other types of electrical generator exist, based on other electrical phenomena such as piezoelectricity, and magnetohydrodynamics. The IEC only standardized binary prefixes in 1999, so 2¹⁰ (1024) bytes was called a kilobyte because 1024 is "close enough" to the metric prefix kilo, which is defined as 10³ or 1000. It is somewhat analogous to a water pump, which creates a flow of water but does not create the water itself. This is largely for historical reasons, since when storage capacities started to exceed thousands of bytes, there were no standard binary prefixes. The generator creates an electric current, but does not create electric charge, which is already present in the conductive wire of its windings. Hard drive manufacturers often use the metric definition of the prefixes "giga" and "mega", whilst nearly all operating system utilities report capacities using binary definitions for the prefixes.

Various versions and improvements have been made since then, but the basic concept of a spinning endless loop of wire remains at the heart of all modern dynamos. In the United Kingdom, Cumana, a manufacturer of disk drives for Acorn computers, ceased manufacturing drives in 1995. His design is now known as the Gramme dynamo. There have also been a number of notable mergers in the hard disk industry:. Zénobe Gramme reinvented this design a few years later when designing the first commercial power plants, which operated in Paris in the 1870s. Rodime was also an important manufacturer during the 1980s, but stopped making drives in the early 1990s amid the shakeout and now concentrates on technology licensing; they hold a number of patents related to 3.5-inch form factor hard drives. This meant that some part of the coil was continually passing by the magnets, smoothing out the current. Many other smaller companies (like Kalok, Microscience, LaPine, Areal, Priam and PrairieTek) also did not survive the shakeout, and had disappeared by 1993; Micropolis was able to hold on until 1997, and JTS, a relative latecomer to the scene, lasted only a few years and was gone by 1999.

Antonio Pacinotti, an Italian scientist, fixed this by replacing the spinning coil with a toroidal one, which he created by wrapping an iron ring. Another notable failure was MiniScribe, who went bankrupt in 1990 after it was found that they had "cooked the books" and inflated sales numbers for several years. Both of these designs suffered from a similar problem: they induced "spikes" of current followed by none at all. The first notable casualty of the business in the PC era was Computer Memories International or CMI; after the 1985 incident with the faulty 20MB AT drives, CMI's reputation never recovered, and they exited the hard drive business in 1987. By adding a commutator, Pixii was able to convert the alternating current to direct current. Dozens of former hard drive manufacturers have gone out of business, merged, or closed their hard drive divisions; as capacities and demand for products increased, profits became hard to find, and there were shakeouts in the late 1980s and late 1990s. Furthermore, the north and south poles of the magnet induced currents in opposite directions. Toshiba is a major manufacturer of 2.5-inch and 1.8-inch notebook drives.

Pixii found that the spinning magnet produced a pulse of current in the wire each time a pole passed the coil. Fujitsu continues to make specialist notebook and SCSI drives but exited the mass market in 2001. The spinning magnet was positioned so that its north and south poles passed by a piece of iron wrapped with wire. Most of the world's hard disks are now manufactured by just a handful of large firms: Seagate, Maxtor (now owned by Seagate), Western Digital, Samsung, and Hitachi, the former drive manufacturing division of IBM. It used a permanent magnet which was rotated by a crank. See also: hard disk drive partitioning, master boot record, file system, drive letter assignment, boot sector. The first dynamo based on Faraday's principles was built in 1832 by Hippolyte Pixii, a French instrument maker. ATA drives larger than 8 GiB are always accessed by LBA, due to the 8 GiB limit described above.

The dynamo uses electromagnetic principles to convert mechanical rotation into an alternating electric current. To maintain some degree of compatibility with older computers, LBA mode generally has to be requested explicitly by the host computer. The dynamo was the first electrical generator capable of delivering power for industry, and is still the most important generator in use in the 21st century. ATA drives can either use their native CHS parameters (only on very early drives; hard drives made since the early 1990s use zone bit recording, and thus don't have a set number of sectors per track), use a "translated" CHS profile (similar to what SCSI host adapters provide), or run in ATA LBA mode, as specified by ATA-2. It produced a small direct current. Because PCs use CHS addressing internally, the BIOS code on PC SCSI host adapters does CHS-to-LBA translation, and provides a set of CHS drive parameters that tries to match the total number of LBA blocks as closely as possible. He also built the first electromagnetic generator called the Faraday disc, a type of homopolar generator, using a copper disc rotating between the poles of a horseshoe magnet. SCSI mode page commands can be used to get the physical specifications of the disk, but this is not used to read or write data; this is an artifact of the early days of SCSI, circa 1986, when a disk attached to a SCSI bus could just as well be an ST-506 or ESDI drive attached through a bridge (and therefore having a CHS configuration that was subject to change) as it could be a native SCSI device.

In 1831-1832 Michael Faraday discovered that a potential difference is generated between the ends of an electrical conductor that moves perpendicular to a magnetic field. SCSI drives, however, have always used LBA addressing, which describes the disk as a linear, sequentially-numbered set of blocks. Electrostatic generators are inefficient and are useful only for scientific experiments requiring high voltages. The 8.4 and 128 GiB limits are soft limits: the PC simply ignores the extra capacity and reports a drive of the maximum size it is able to communicate with. The Van de Graaff generator uses either of two mechanisms:. The 2.1, 4.2 and 32 GiB limits are hard limits: fitting a drive larger than the limit results in a PC that refuses to boot, unless the drive includes special jumpers to make it appear as a smaller capacity. The Wimshurst machine used electrostatic induction or "influence". Even after the introduction of LBA, similar limitations reappeared several times over the following years: at 2.1, 4.2, 8.4, 32, and 128 GiB.

Before the connection between magnetism and electricity was discovered, generators used electrostatic principles. When drives larger than 504 MiB began to appear in the mid-1990s, many system BIOSes had problems communicating with them, requiring LBA BIOS upgrades or special driver software to work correctly. . The origin of the CHS limit lies in a combination of the limitations of IBM's BIOS interface (which allowed 1024 cylinders, 256 heads and 64 sectors; sectors were counted from 1, reducing that number to 63, giving an addressing limit of 8064 MiB or 7.8 GiB), and a hardware limitation of the AT's hard disk controller (which allowed up to 65536 cylinders and 256 sectors, but only 16 heads, putting its addressing limit at 2^28 bits or 128 GiB). The process is known as electricity generation. The traditional CHS limit was 1024 cylinders, 16 heads and 63 sectors; on a drive with 512-byte sectors, this comes to 504 MiB (528 megabytes). An electrical generator is a device that produces electrical energy from a mechanical energy source. CHS describes the disk space in terms of its physical dimensions, data-wise; this is the traditional way of accessing a disk on IBM PC compatible hardware, and while it works well for floppies (for which it was originally designed) and small hard disks, it caused problems when disks started to exceed the design limits of the PC's CHS implementation.

Generator Facts. The more recent mode is the LBA (Logical Block Addressing), used by SCSI drives and newer ATA drives (ATA drives power up in CHS mode for historical reasons). Electus Distribution Reference Data Sheet: Impedance Matching Primer (PDF). The older mode is CHS addressing (Cylinder-Head-Sector), used on old ST-506 and ATA drives and internally by the PC BIOS. Patent 447921 -- Alternating Electric Current Generator - Tesla's generator that produces alterations of 15000 per second or more. Addressing modes There are two modes of addressing the data blocks on more recent hard disks. U.S. Most FireWire/IEEE 1394 models are able to daisy-chain in order to continue adding peripherals without requiring additional ports on the computer itself.

Patent 447920 -- Method of Operating Arc-Lamps - Tesla's alternating current generator of high frequency alternations (or pulsations) above the auditory level. FireWire/IEEE 1394 and USB(1.0/2.0) hard disks are external units containing generally ATA or SCSI drives with ports on the back allowing very simple and effective expansion and mobility. U.S. Serial ATA does away with master/slave setups entirely, placing each drive on its own channel (with its own set of I/O ports) instead. (Related to patents numbers US327797, US292077, and GB9013.). This was mostly remedied by the mid-1990s, when ATA's specfication was standardised and the details began to be cleaned up, but still causes problems occasionally (especially with CD-ROM and DVD-ROM drives, and when mixing Ultra DMA and non-UDMA devices). Patent 417794 -- Armature for Electric Machines -Tesla's construction principles of the armature for electrical generators and motors. ATA drives have typically had no problems with interleave or data rate, due to their controller design, but many early models were incompatible with each other and couldn't run in a master/slave setup (two drives on the same cable).

U.S. The SCSI bus speed had no bearing on the drive's internal speed because of buffering between the SCSI bus and the drive's internal data bus; however, many early drives had very small buffers, and thus had to be reformatted to a different interleave (just like ST-506 drives) when used on slow computers, such as early IBM PC compatibles and Apple Macintoshes. Patent 406968 -- Dynamo Electric Machine - Tesla's "Unipolar" machine (i.e., a disk or cylindrical conductor is mounted in between magnetic poles adapted to produce a uniform magnetic field). SCSI originally had just one speed, 5 MHz (for a maximum data rate of 5 megabytes per second), but later this was increased dramatically. U.S. ESDI drives typically also had jumpers to set the number of sectors per track and (in some cases) sector size. Patent 359748 -- Dynamo Electric Machine - Nikola Tesla's construction of the alternating current induction motor / generator. a 15 or 20 megabit drive wouldn't run on a 10 megabit controller).

U.S. ESDI also supported multiple data rates (ESDI drives always used 2,7 RLL, but at 10, 15 or 20 megabits per second), but this was usually negotiated automatically by the drive and controller; most of the time, however, 15 or 20 megabit ESDI drives weren't downward compatible (i.e. Patent 373,584 -- Dynamo-Electric Machine : Edison's improved dynamo which includes an extra coil and ultilizes a field of force. (An RLL-certified drive could run on a MFM controller, but with 1/3 less data capacity and speed.). U.S. In some cases, the drive was overengineered just enough to allow the MFM-certified model to run at the faster data rate; however, this was often unreliable and was not recommended. It is inefficient. Many ST-506 interface drives were only certified by the manufacturer to run at the lower MFM data rate, while other models (usually more expensive versions of the same basic drive) were certified to run at the higher RLL data rate.

This device has large bipolar magnets. Later on, controllers using 2,7 RLL (or just "RLL") encoding increased this by half, to 7.5 megabits per second; it also increased drive capacity by half. The device's nickname was the "long-legged Mary-Ann". The first ST-506 disks used Modified Frequency Modulation (MFM) encoding (which is still used on the common "1.44 MB" (1.4 MiB) 3.5-inch floppy), and ran at a data rate of 5 megabits per second. Patent 222,881 -- Magneto-Electric Machines : Thomas Edison's main continuous current dynamo. Back in the days of the ST-506 interface, the data encoding scheme was also important. U.S. A hard disk is generally accessed over one of a number of bus types, including ATA (IDE, EIDE), Serial ATA, SCSI, SAS, FireWire (aka IEEE 1394), USB, and Fibre Channel.