Categories

AC Power Source

Frequency (50Hz, 60Hz) in Generators

Wednesday, January 14, 2015

The excitation system requires a very small fraction of the total power being generated. If we could simply increase the excitation (a very small amount of power) and increase the generator's real power output, the world's energy problems would be solved, because we would have a perpetual motion machine.

In the case of a generator connected to a large grid, the generator will inject any desired amount of power into the grid if its prime-mover is fed the desired power (plus a small ...

Monday, January 12, 2015

Distributed generation generally means more than one power source feeding the same loads including sources at multiple locations but it can also mean stand alone or isolated generation at the point of use. Typical for this definition are generator and UPS at mission critical sites such as data centers and laboratories. These can operate in complete isolation, in parallel with the utility grid, in parallel as part of a local grid. Power can also be transferred between the utility grid and loca ...

Smart Grid Utilities

Saturday, January 10, 2015

This is my 39th year working for or calling on electric utilities. I have not seen any ulterior motives. Many of my utilities have electively chosen not to add smart meters due to cost, and due to competition.

The excitement of smart grid, seems to be driven more by media and the "sexiness" of the idea that everything from generation of all kinds to loads in a home can be matched w/o human intervention. Practically speaking utility engineers have been "automating for decades, cons ...

Difference between transient recovery voltage and restriking voltage

Sunday, January 4, 2015

Transient recovery voltage generally occurs because of current chopping phenomena before natural current zero. In case of low current there may be a chance of current Chopping i.e. ARC INTERRUPTION before natural current zero, so whatever the stored magnetic energy i.e. 1/2 Li^2 present in the circuit is converted in to electrostatic energy i.e. 1/2 CV^2. So generated transient recovery voltage = (L/C)^1/2 X i

Now because of transient recovery voltage dielectric strength of dielect ...

Voltage Frequency Levels of Power System

Saturday, January 3, 2015

The voltage levels, particularly at the high-voltage and extra-high-voltage levels, have long been standardized in different industrialized countries. The North-American system is 60 Hz, while the European system is 50 Hz. Each other country in the world (as far as I know) follows one or the other frequency standard. Japan is the only country I know of that has both 50 Hz and 60 Hz systems.

Then, once you've picked your "system ...

How to be a good sales for an engineer in power supply industry?

Thursday, January 1, 2015

An engineer may think sales is difficult because he doesn't have the skill set or it doesn't align with his natural strengths. Been there done than for me also. However, I'm able to use my technical skills to help my company get orders. I sell but not in the way most people would think. Realize that many times you don't have to SELL to obtain an order. Hopefully you have a natural interest, better yet a passion, for the electric power industry, and you're not in it just because you see a high ...

What happens if plug an 110V appliance in 220V socket?

Wednesday, December 31, 2014

It depends upon the nature of the appliance but generally speaking if the voltage is too high it draws too much current and burns out, if the voltage is too low it draws too little current and/or does not perform to its rating. The mathematical reference is Ohm's Law and the Power Triangle.

If you plug an 110V appliance in 220V outlet (same as 120v to 230v, 240v) you can only hope that some protection device disconnects the power to the appliance.
Otherwise: ...

Why we use 3 phase power supply, not 4/5/6 phase

Wednesday, December 31, 2014

Single-phase motors have unambiguous rotation (with a capacitor start), and with a center tap neutral, a single-phase system can be balanced.

I'm not sure regarding the economics of multi-phase systems. It seems to me that for each phase added, the total power capacity is increased by one line-ground voltage times one line current so there is no natural less-costly number of phases. There have been "economic" arguments for six-phase systems decades ago, but the reason for six-phas ...

What is Power Factor and How to improve it?

Tuesday, December 30, 2014

Power Factor is defined as the ratio of the active power to total power. When the load has linear behavior (motor for instance) the current is sinusoidal and power factor equals the cosine of the angle between current and voltage. Voltage (or current depending on the circuit) injection is used in nonlinear circuits in order to increase Power Factor.

In case of nonlinear loads, generally associated with power supplies and rectifiers used to feed computers and battery chargers, the i ...

Why generator voltage is 11kV 50Hz or 13.8kV 60Hz?

Tuesday, December 30, 2014

The real reason behind the choice of 11, 22, 33, 66 and 132kV levels is not clear from the responses to date and it may have passes into history unknown. Most likely, it was a decision arising from a standards committee and it may be an optimum transformation ratio chosen to minimize total losses. Someone still alive may yet know the reason. Then again, it may have a legacy resembling that of the standard rail gauge.

These numbers were chosen arbitrarily in the past and have actual ...

GoHz Frequency Converter 50Hz 60Hz Settings

Saturday, December 27, 2014

Following texts are the video transcription of GoHz frequency converter parameter setting.

First, we see the frequency converter panel of parameter settings, there are total 10 parameter sets, count from M0 to M9, each parameter set store the values of voltage, frequency and running time. Press the UP/DOWN buttons to select which parameter s ...

Using a 3 phase inverter power back to AC source

Saturday, December 27, 2014

Wound rotor motor is not the best option for SAG mills because the slip rings always are a problem even with liquid resistors. Best option is synchronous motor in combination with variable frequency drive. However if you already have the wound rotor motor the ERS operation is simple.

Instead of dissipating the rotor power in a resistor we can use it to power a 3 phase inverter that returns the power to the AC power source. The line commutated i ...

Why voltages in 110V, 220V, 440V...?

Friday, December 26, 2014

Why Transmission, distribution and utilization voltages are in multiples of 11, as in 110V, 220V, 440V, 1.1kV, 3.3kV, 6.6kV, 11kV, 22kV, 33kV, 66kV, 110kV, 132kV & 220kV?

It is true only with respect to AC power supplies. The first known man-made source of electricity is a cell, which is DC in nature. But, after realizing the disadvantages of the DC electric equipment, AC Electricity generating machines were invented. When these AC Machines w ...

GoHz Frequency Converter Operation Guide

Wednesday, December 24, 2014

GoHz frequency converter is a great solution for converting 50Hz to 60Hz among different countries, also can convert 60Hz to 50Hz, in additional of frequency adjusting, the output voltage is changeable from 0-300 volts for single phase power supply, 0-520 volts for three phase power supply. This article shows the basic operation guidelines of GoHz static frequency converter, you can easy set up a converter by following this guide. ...

Operating 50Hz transformer on 60Hz supply

Wednesday, December 24, 2014

You can run the 50Hz transformer on a 60Hz supply. Now since the frequency has changed the only variable thing in the existing transformer that can change (assuming simple one input and one output) is the flux density. In its simple form we are operating the transformer (60Hz/50Hz = 1.2) at 20% lower flux density.

If the things were reversed the flux density would be 20% higher and may saturate depending on design. You can even run the transformer at 400Hz providing that the volta ...

Why Three Phase AC System was created?

Saturday, December 20, 2014

There is a widely spread error that it was introduced by Nicola Tesla. Nicola Tesla was mostly interested in 2-phase system that is usually referred as "poly-phase" system in the USA. He also created 2 phase induction motor. You can find a picture of that design from Internet. (I should mention, the first induction motor was invented and built by Ferraries from Italy, it was single-phase one and had slipping of 0,5!!! As result, efficiency was very low).

The 3-phase system was deve ...

Convert AC to DC power

Wednesday, December 17, 2014

For the Logic Power supply I want to convert AC 120/240V to 24/15/5/3.3 VDC. I am wondering what is the best topology to do this. Currently I am using a power transformer to convert down to 24vac rectify and tap off of that. Is there a way to reduce/remove the power transformer? Should I change to a flyback style of converter? I need about 5-10 Watts DC power total.

If you do not care about power factor (means no need of power factor correction), then indeed a possible solution is ...