Electrical Engineering

A 400 MCM copper conductor with an insulation temperature factor of 90 degrees C is rated at 380 amps.A 500 MCM copper conductor with an insulation temperature factor of 75 degrees C is rated at 380 amps.

These conductors can have either 600 or 1000 volt insulation rating depending on what the system voltage in use is.

Probably; it is a difference of less than 4%. And since the voltage is slightly too low, you won't burn the motor - having too high a voltage is more risky.

Let me start answering this question by clarifying the terminology used by PTCRB. Here are some important definitions taken from PTCRB NAPRD03:

End product:

End Products are defined as devices that

-Utilize a standard interface (USB, PCMCIA, Compact Flash, MMC, RS-232, IEEE-1394.)

-Obtain power from the standard interface or have a provisioned power source

-Include a fully self-contained USIM/SIM socket

-Utilize a self-contained antenna or provide an external antenna connector.

When an End Product is connected to (but not embedded within) a host device (PC, PDA, etc.), no certification of the host device is required. By its design and intended user application, an End Product must be consistent with the terms of its FCC / IC type acceptance (e.g. type of antenna, distance from user, etc.). In all cases, the End Product shall not alter its antenna system in any way from that allowed by the associated Type Acceptance or other regulatory approval.

Integrated Device:

Any device type that embeds a PTCRB-certified module. In order to be considered an integrated device, the PTCRB-certified module must be embedded in full accordance with the module's Initial PTCRB certification.

Module:

Modules are devices that do not directly connect to a host via a standard interface. A module may or may not include its own antenna system. Modules almost always require additional certification when integrated within another device.

For further clarity:

If you are interfacing your custom circuitry/computer to a PTCRB End Device using an industry standard interface, then no further certifications are required.

PTCRB certified modules(aka integrated modules), in my opinion, should be called "pre-certified" because they all have to be certified again on the final platform of the End Product, which costs between $27k-45k according to AT&T.

Where the question is most relevant is regarding some of the modules coming onto the market that claim they are PTCRB certified. The grey area is that they are actually an Integrated Device where the module has been certified and then integrated onto a carrier board that has been PTCRB approved on a specific test platform, and as long as you employ the "module" in the manner in which they were certified then they do not require additional PTCRB certifications. Buyer beware on these modules - if it does not fall into the PTCRB definition of the End product, then your safest assumption is that it will require additional PTCRB certifications(take it from me - I have been burned with this once!).

Some good due diligence to do would be to contact the vendor to verify their PTCRB certification, and how it was certified. Follow it up and contact their test lab to confirm how the device is certified to be used. At a minimum, the most important thing to do is to contact the wireless service provider to see if they will permit the device on their network as they are ultimately the ones with the final say.

Yes, the Japanese system uses magnets that attract, then repell the train.

EDS - ElectroDynamic Suspension (Japan) - "pull, neutral, push" system. Superconducting magnets in the train are pulled forward by track magnets. When the train is over the track magnet the track switches to neutral, then to the opposite polarity. So the magnet behind the train then pushes it forward.

Ohm's law states that "The current is directly proportional to the applied EMF (voltage) and inversely proportional to the resistance in the circuit."

If the voltage across a circuit increases, then the current will increase too. If the ratio of voltage to current is constant for variations in voltage, then the circuit is described as being 'linear' and is obeying Ohm's Law; if the ratio of voltage to current changes (as it would, for example, with tungsten) for variations in voltage, then the circuit is described as being 'non-linear', and is not obeying Ohm's Law. This is because Ohm's Law is not universal, and only applies to certain materials; in fact, most materials and electronic devices do not obey Ohm's Law.

Welll, it's actually a lot like the difference between a mile-per-hour and cars,

or between an inch and people.

-- "Watt" is a unit of measure that describes the rate at which energy is used,

or produced, or moved from one place to another.

-- "Sunlight" is a small portion of the stupendous amount of energy that the sun

produces and pours out in every direction at a humongous rate.

It is a silicon-controlled rectifier, converting AC to DC for use in drawworks, mud pumps, etc.:

silicon-controlled-rectifier

http://sourceforge.net/projects/javacalltracer

It is a very lightweight tool and you can control what you want to generate and see in the sequence diagram.

Here is a brief description from the MaintainJ homepage:

MaintainJ, an Eclipse plug-in, generates runtime sequence and class diagrams for a given use case, helping the users to quickly understand a complex Java or J2EE application.

MaintainJ logs runtime method execution sequence to a file and uses that trace file to render sequence and class diagrams. MaintainJ Instrumentation Wizard instruments a Java/J2EE application and MaintainJ UML Editor renders sequence and class diagram from the trace file.

The following features make MaintainJ a unique and useful tool for Java developers.

a) Generated Diagrams - Runtime sequence and class diagrams for a given use case are generated on demand in a few minutes; no need to prepare and update UML diagrams.

b) Source Untouched - The application code is not changed in anyway; application is rebuilt using AspectJ compiler to capture the method execution sequence at runtime.

c) Collapsible Calls - Method calls in sequence diagram are collapsible. One can easily explore a complex sequence diagram by collapsing and expanding calls as necessary.

d) Focused Diagrams - Only application classes in specified packages are shown in diagrams. All repeat calls occurring in a loop and recursive calls are removed from sequence diagrams.

e) Runtime Diagrams - All classes shown in the diagrams are concrete runtime classes.

f) Eclipse Integration - Double clicking a call or class opens matching method or class in Eclipse.

g) Outline Views - Outline views in both diagrams make navigating a complex diagram easier.

h) Print or Export - Diagrams can be printed or exported as JPEG images.

jTracert will allow you to generate sequence diagrams directly from your application runtime!

jTracert is implemented as a small javaagent, consisting from only one jar with no dependencies. In order to profile your application with jTracert, just add the following option to VM options: -javaagent:jTracert.jar

So your full command line will look like below: java -javaagent:jTracert.jar -jar yourApplicationJar.jar

Please note, that you're not limited to J2SE applications. Add this parameter to your J2EE App server options, and profile your J2EE application. It's also possible to profile applets, and almost all other types of java applications. This is a benefit of implementing jTracert in pure Java.

Note: as of 30 Mar 2010 jTracert has been replaced by jSonde (which is also free). See http://www.jsonde.com

Reverse java works with both any standalone Java application or a Web based J2EE application.

• If you are referring to a megohm meter, it is a test of the insulation properties of such things as electric wiring, motor windings and high power antenna mounts.

  We use a "megger" or "meg out" electrical wiring and equipment to see if it is shorted to ground in any way.

  The megger uses much higher voltages to check resistance than a normal Volt-ohm meter.

  Ideally, you want infinity resistance but I've installed 460 volt motors with 750 meg ohms resistance to ground and had no problem.

• On the whole megger testing is non destructive. What happens is a DC voltage is applied to the device or winding under test. It is an insulation test to see is the insulation has been injured in any way to cause a short circuit when normal power is applied to it.

  On my megger there are 3 ranges 300V, 750V, and 1000 volts. Applying the proper voltage is essential to not damaging the device you are testing.

  Working voltages up to 240 volts should use the 300 range.

  Working voltages up to 600 volts use the 750 volt range and working voltages above 600 use the 1000 volt range.

  As you can see if you used the 1000 volt range on a device that had a working voltage of say 24 volts you could damage the insulation just by testing it. So meggering a device is non destructive if you use the tester as its instructions tell you to.

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As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.

Before you do any work yourself,

on electrical circuits, equipment or appliances,

always use a test meter to ensure the circuit is, in fact, de-energized.

IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB

SAFELY AND COMPETENTLY

REFER THIS WORK TO QUALIFIED PROFESSIONALS.