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Motor Drive
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All computer drives will fail. This is why they are only warranted for a couple of years. When they fail the data on them is usually still there, but cannot be pulled off the drive for some reason. I will try to explain how to go about recovering data from a hard drive in these situations.

While this is a simplified version of how to recover data from a failed computer disk just to help you understand what is involved. It is NOT a definitive procedure for recovering data.

One of the ways that a hard drive can fail is for Windows to fail to boot, thereby trapping your information in such a way that you cannot get to it. When this happens simply repairing windows will probably make all your data available.

Another way you may lose data is because you deleted something, or formatted a drive that had something you need to recover. Data recovery software can often be used for this purpose, and many things can be recovered. Perhaps a different article someday.

However, this article will concern itself with recovering data when the drive is no longer able to be accessed by the operating system.

Hard drives tend to fail because of one of these reasons:

• The motor dies
• The controller dies
• The firmware becomes corrupted
• The read -write heads become misaligned
• The surface if the disk platters begin to degrade.

Mechanically, hard drives are not a really complicated device. Basically it is a metal case, with a motor mounted into the floor of it. This motor has a spindle on it similar to what your car has on its rear wheels. Instead of wheels and tires, this spindle has some small extremely thin discs, called platters attached. When the drive is turned on, the motor spins the disks. Above, in between, and below the platters there are little arms that travel across the surface of the disks using something called a read-write heads to read and write (get it?) little magnetic spots on the surface of the platter. Oh yeah, there is a magnet in there too.

All of this is controlled by a circuit board attached to the hard drive. This board has a small software program on it (referred to as firmware) that operates the hard drive. If you have an old hard drive, turn it over and look at where the cable connects to the drive. This connection is on the controller for the hard drive. If you touch any of the circuit board with your finger you can kill the drive by shorting the controller out with static electricity. Always handle a hard drive by the case, and take extreme care about static electricity.

When you send a hard drive to have the data recovered, the recovery company will hook it up and see if the hard drive will spin. If it will, then they will reload the firmware to the controller, and see if that works. If it doesn't, they may replace the controller board with a known good part and see if that will work.

Sometimes, especially if the drive has been dropped, the drive case has to be opened, and the read-write heads have to be re-aligned or replaced in order to recover the data stored on the drive. When all else fails, or if the drive will not spin, the drive will be disassembled, a new drive of the same model is also disassembled, and the platters that have the lost data are installed into the new drive housing in order to recover the data.

If the surface of the platters has begun to degrade, the chances of loosing data skyrocket. Always backup your data, and never keep irreplaceable files on a hard drive more than 2 years old.

These complications mean that data recovery is a very expensive procedure to have done, and the results are unpredictable.

Steve is a 35 year veteran in the IT industry, and owns a computer repair service in Houston TX as well as a number of web properties including a free computer repair help website.

What is a Medium Voltage (MV) AC Drive (Frequency Inverter)?

What is a Medium Voltage (MV) AC Drive (Frequency Inverter)?

 

Don't feel bad about being confused by "medium voltage drives" terminology. It's a confusing because it sounds like a technical term, but really it's marketing driven. Actually, there are two terms that can be confusing to anyone new to the field of automated control of electric motors.

Let us start with the word "drive." Also sometimes called an inverter, a drive is essentially a power amplifier that puts out the electric power needed by an electric motor based on the torque and/or speed called for by the controller, which is a digital computer tasked with overall system control. As the industry has shifted in favor of variable-speed drives, the role of the drive has become more important.

Variable-speed motor/drive combinations use a synchronous ac motor with an encoder built in. The encoder signals the motor's speed and phase angle to the drive, which must then match its output frequency to the motor speed and its output phase to produce the required torque.

To get the drive's power efficiently out to the load as mechanical power requires having enough voltage to drive enough current through the motor. The output power is, after all, the product of voltage times current. The ratio of the voltage to the current, on the other hand, defines an impedance for the drive/motor combination.

Copper resistance in the motor coils and power cables, as well as contact resistance in all the connections rob the system of power, however. The higher the circuit impedance compared to these parasitic impedances, the more efficient the overall system will be.

The graph below compares motor/drive impedance to a typical parasitic impedance level of one Ohm. Assuming we want the ratio to be one or two orders of magnitude, the chart shows how the supply voltage needed correlates with output power. Small, fractional horsepower motors (red line) work well from a few tens to a few hundreds of Volts. Larger motors require hundreds of Volts to run efficiently. As horsepower requirements climb, so do the drive voltage requirements.

What really drives people crazy is the term "medium voltage drive." It is a purely marketing term. From zero to 600 V is called "low voltage (LV)." "Medium voltage (MV)" is 600 V and above. There is no "high-voltage (HV)" designation.

Comparing this 600 V cutoff to the chart shows that low-voltage drives provide good efficiency up to several horsepower (10,000 W). Above 10 kW, however, medium voltage drives are needed. Voltages above a few thousand Volts, however, are needed only for the relatively few electric motor applications requiring hundreds of horsepower. Most applications requring that much mechanical output are currently served by internal combustion engines.

About the Author

Engineers and sales of frequency inverters, ac drives in China

Is the Zhumell Eclipse 114 with Motor Drive Reflector Telescope a good one.?

What does the motor drive do? I know it says it helps you find stuff easier. But I do not understand how or what that really means...
Also, what are the eye pieces for? Here is the link for the telescope...

http://www.telescopes.com/telescopes/reflecting-telescopes/zhumelleclipse114withmotordrivetelescope.cfm

Thank you.

No, this is a very poor telescope, and I would not recommend it to anyone. It uses a short focal ratio spherical mirror and a built-in Barlow lens to achieve its focal length; this design is hard to adjust and suffers from serious optical flaws preventing it from magnifying more than about 100x. The tripod and mount are shaky and will be very difficult for a beginner to operate. The motor drive compensates for the Earth's rotation once you've found something, but does not make finding objects any easier.The eyepieces provide different magnifications.

Here are a few web pages with good information on beginner's telescopes:
http://www.gaherty.ca/tme/TME0702_Buying_a_Telescope.pdf
http://www.scopereviews.com/begin.html
http://observers.org/beginner/j.r.f.beginner.html

For more advanced information, read Phil Harrington's Star Ware, 4th edition (Wiley).

You'll get the greatest value for your money with a Newtonian reflector on a Dobsonian mount, such as these:
http://www.telescope.com/control/category/~category_id=dobsonians/~pcategory=telescopes/~VIEW_INDEX=0/~VIEW_SIZE=1000000
http://www.skywatchertelescope.net/swtinc/product.php?class1=1&class2=106

Buy from a store which specializes in telescopes and astronomy, either locally or online; don't buy from department stores, discount stores or eBay as mostly what they sell is junk. Find your local astronomy club and try out different telescopes at one of their star parties:
http://www.skyandtelescope.com/community/organizations

Disabled students concerned about Campus Drive closure
By: Nelly Desmarattes University to close main road as test over the summer The planned summer closure of Campus Drive to most motor vehicles has some disabled students concerned about access to classes and navigating the steep campus hills. The plan “will be a pain for everyone, but it will have a disproportionate impac...

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