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Guys, Thank you all very much for the responses. Although no definite answer has been determined, the information that you provided was very interesting. I guess that variety truly is the spice of life. Regards, Raisinbran

Gentlemen, Maybe this question has been raised before. What are the reasons for the differences in voltage levels between the US and Europe - 4.16 kV (US) vs. 3.3 kV (Euro.) and 7.2kV (US) vs. 6.6 kV (Euro.)? Does it have anything to do with the 50 Hz. vs. 60 Hz. frequency differences...

Gentlemen, Our coal mining company is setting up training facilities to train our mine electricians on how to safely troubleshoot our equipment. The supply voltages to this equipment would be either 480 volts (3 phase) or 950 volts (3 phase). When being used underground, our equipment is...

Gentlemen, There should be a relationship between short circuit MVA at any point in a distribution system and the voltage drop that occurs when a motor is started at that same point in the system. Is there a straight forward relationship between the two or does the voltage drop also depend...

We have an installation where we may want to run two AC three phase generators from one common driver. The generators will then be connected in parallel electrically. Since they are both driven from a common driver, they are also in parallel mechanically. I have heard that there may be some...

First - I hope that everyone is enjoyng the Holiday Season and spending some relaxing time with family and friends. We manufacture gearing and couplings to coupler diesel engines to three phase generators. The generator size is 2- 2.5 MW. The generators are 60 Hz, and the output voltage...

This is for a mining application where the ground fault current is limited to 0.5 amperes. It trips at 200 ma. This type of a system is used quite often, but it appears to violate some of the equations used for sizing NGR that I have seen. This is on a 480 volt system, but the same is true...

If I wanted to install a resistance grounded system (480 volt or 4160 volt), I know that there is a theoretical maximum resistance that is recommended. If I remember correctly, it is based on the system charging current. Can anyone help me with this issue? Regards, Raisinbran

Thanks to all for your valuable input. I am sure that I will have more questions, but I now have an excellent starting point. Regards, Dave

ScottyUK My fault. I am not familiar with all of the various equipment terminology, and I used the words "recloser" and "synchronizer" inter-changeably. Synchronizer is the correct word. To prevent the problem that I am concerned about, what are accepted values for phase angle difference and...

I am looking for possible causes of damage to the gears/bearings in a speed-change gearcase that couples a large diesel engine (2000 kW) to a 2700 kVA generator. This system is connected to other generators and the utility thru a set of circuit breakers. One theory is that the gen-set circuit...

Capacitors "blowing up" is typically a sign of over-voltage. Possibly, you worked yourself into a resonant condition? Just a thought, Raisinbran

This may not be practical in your situation, but noise reduction is one of the benefits of using water cooled motors. We use them quite often in the underground mining industry. If you have a process nearby that requires water, maybe it is something you can look at. If you cannot use water...

Jfpe, It sounds like you have effectively given the neutral current existing in the system another path to flow. I would suspect that the neutral current in the source transformer became higher when the neutral in your isolation this transformer was disconnected. If it is truly an isolation...

Gentlemen, My background is Electrical Engineering, so excuse me if I don't use the correct terminology. We use several helical gearboxes at our plant. They are parallel shaft, single reduction units. Each shaft is approx. 6 inches in diameter. Input shaft speed is 1800 RPM. Each shaft is...

Edison 123, I would be tempted to leave the bearings as is. In a solidly coupled configuration, you want the axial shaft growth to be opposite of the driven machine, in your case - out the back end of the motor. This way, the motor shaft can do what it has to do and not interfere with any other...

rbyrne15, These terminals are used for a modified primary injection test. An example would be 100:5:5 ratio - (primary:secondary:test). A small test current is injected into the 5 ampere test winding. A replica current is generated in the 5 ampere CT secondary winding which is then fed to the...

Hello All, My background is electrical engineering, so I apologize if I do not understand the proper terminology. We have had a gearing failure and there is some dispute as to what has caused the failure. The gears are straight spur gears and reduce the speed from 1800 rpm to around 500 rpm in...

SparksZA, We use a variety of water-cooled motors in the underground coal mining industry, primarily to take advantage of the power density as UKPete mentioned. The water jackets that we use are essentially "added on" to the motor housing, so cooling water getting into the motor is generally...

We have a situation where it would be advantageous to run a higher voltage power line (34.5 kV)underneath of a lower voltage (4.16 kV)power line. Both lines are on poles, but serve only our needs - mining. Assuming that we maintain adequate clearances, are there any rules/standards to prevent...