Blog

The Simple rule which normally dominates the selection of vector group of a transformer is the network where it is to be installed. Normally there are three networks: Generation, Transmission and Distribution. The inherent advantage of the D connection is prevention of zero sequence and harmonics to enter in the network.

Now starting from the Generation. The generators are connected in the Y. Now from the Generators the Unit Transformers are used to transmit the power. The prefera ...

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 ...

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: ...

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 ...

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 ...

You already know from your engineering that higher voltages results to less operational losses for the same amount of power delivered. The bulk capacity of 3000MW has a great influence on the investment costs obviously, that determines the voltage level and the required number of parallel circuit. The need for higher voltage DC levels has become more feasible for bulk power projects (such as this one) especially when the transmission line is more than 1000 km long. So on the economics, invest ...

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 ...

To cater the single phase loads from the 3-Phase inverters, all inverter designers will use the system neutral which is used for the load distribution as well will be used as reference in order to develop the sinusoidal output phase waveform. So, every manufacturer uses different techniques depending upon the technology. But, whatever may be the technology the manufacturer uses, he has to take the neutral (which is the return path for the single pha ...

Case: I have a VFD installed at my plant to run a 500 hp motor. Recently we had an incident of motor tripping on Ground Fault. The motor's insulation resistance was tested & the results showed that winding was grounded. After repair, the motor was again connected to the VFD & started but the VFD tripped the motor on "Inverter Ground Current". I checked the insulation resistance of motor & cable but the values were in Mega Ohms. I even checked the VFD physically to ensure that the ...

It's been nearly 30 years since my first encounter with harmonics due to switching mode power supplies. A 75 KVA transformer with almost no measurable load using a conventional clamp on ammeter was so hot I couldn't touch it for more than a couple of seconds without getting burned. Thermoscanning showed up cherry red. Switching the transformer to a 112.5 KVA known to be reliable helped some. The source of much of the harmonics was a large photocopy machine. Ever science it has become increasi ...

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 ...

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 ...

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 ...

Assume a pure inductive load connected across an AC power supply, we will see that, the power wave has double frequency that of the voltage wave that produced it. In other words we can see that, by the time voltage wave completes one half cycle, the power wave would have completed one complete cycle. By definition, this power is called the reactive power.

We can see that, this power (reactive) consumed by the inductor is zero in any half cycle of voltage wave. Physically speaking, ...

In hundreds MW plant we are using static excitation system, but it require more maintenance than brushless. Why not we are going for brushless system? What is the reason behind this?

As far as I know, the increased maintenance requirement is associated with the slip rings and brushes. It is not so easy to replace a static excitation system with a brushless system, as you'd have to change things in the machine rotor and shaft (remove the connections to the brushes and slip rings, ad ...

Induction motors operate on the principle of current induction in the rotor which must rotate at a speed less than synchronous speed for induction to occur. This is referred to as slip speed and should not be confused with pole slipping.

Why induction motors have no pole slipping and why other motors have pole slipping? I will attempt to answer this for you but first let's define poles and synchronous speed in regards to electric motor operation.

Poles in an electric m ...

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. ...

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 ...

For Metro DC traction power systems, the commonly adopted nominal voltages are 750V DC and 1500V DC. The DC substations are normally fed from a High Voltage (HV) 11 kV or 33 kV 3-phase AC network in the UK. To convert the 3-phase AC voltage to DC voltage, a modern DC substation employs a 3-winding transformer (delta-delta-star) to feed a 12-pulse rectifier (consisting of 2 x 6-pulse diode bridges, the outputs of which are connected in either parallel or series to form a 12-pulse rectifier). N ...

Many people think that UPS is a magic box that solves all the electrical problems. UPS systems have capacities varying from few hundreds of VAs to massive kVAs. The only thing that is worth noting in a UPS system is that, it can be viewed as a source as well as a load. Depending upon the configuration, the grounding needs to be planned. If the UPS system is transformer based, and operating only in inverter mode (Frequency converter mode), then it is called as separately derived source and out ...