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# AC Power Source

#### Why we use 50Hz, 60Hz or 400Hz frequency?

##### Thursday, January 12, 2017

Why the frequency of power supplies in European and Asian countries is 50Hz, while American countries use 60Hz power supplies? What is the basic of the standard? What are the advantages and disadvantages of 50Hz and 60Hz power supply? In addition, why the airport and aircraft use 400Hz frequency?

In fact, there is no big difference between 50Hz and 60Hz, only the generator speed has slightly difference. C ...

#### How can we get 1-phase 240v from 3-phase 11kV transformer?

##### Tuesday, December 6, 2016

In Europe we have a 1-phase 220v/240v power supply to home, which is ONE hot line, unlike America that have TWO hot lines (120v of each) into their homes which is therefore logically and technically a 2-phase power supply, even if they will admit the obvious.

There are two ways we can be feed our 1-phase supply from the pole mounted 3-phase 11kV line. The primary of that transformer can be feed from either one of the 3-phase lines, that would be 6.4kV to Earth, or feed from two of ...

#### The Concept of Harmonic Loads

##### Thursday, November 24, 2016

Harmonic waves are commonly generated by any equipment that utilizes capacitors, think VFD and a multitude of single phase equipment. You will probably have to install power factor correction to get the best from your generators and these capacitors also generate harmonics. Unlike faults, the harmonics generated are not likely to trip the equipment circuit breakers and thus affect the power supply system. It causes ripples in the voltage sinus wave, one effect this produces in practical terms ...

#### Under Frequency Operation of Power System

##### Saturday, October 29, 2016

An established grid operating at a certain frequency (say 60 Hz) would have a certain inertia associated with this particular frequency. Given that it's possible to instantaneously drop the system frequency without losing sync, then, if we operate at a lower frequency, can we get some extra power injected to the system?

The grid standard for power quality dictates the frequency deviations allowable. Keep in mind that some electrical equipment are frequency sensitive. On the other h ...

#### Can I increase the generator output power by increasing its speed?

##### Saturday, October 15, 2016

IF you are connected to STIFF grid, yes. If your generator is connected to a soft grid, it's different.

By definition, if this generator can impact the Hz or V of the grid, it is a soft grid to this generator's control system. For example, two 10MW generators and no grid connection. One generator can "push" the other around up to some point. It is NOT size dependent: you can parallel a 10MW with a 10kW and to the 10kw, it is a stiff grid. To the 10MW, it is a soft grid.

...

#### Instruction of GoHz Frequency Converter Remote Controlled by PLC

##### Sunday, October 9, 2016

While switch to "self-control", all of the output parameters are controlled by the frequency converter, at the moment, all external controls are inoperative;

While switch to "external PLC control", the keyboard of the frequency converter is inoperative, all control commands are transmitted by external PLC, refer to following instru ...

#### Is it possible to connect the bus-tie for all the time?

##### Friday, September 23, 2016

In EHV/HV system where more than 1 -in coming power supplies are received from Two of more Power sources (synchronized). Supposing one source is in one direction of the station where as the other is on the opposite direction of the station. If feeding from one source fails the supply to all the feeders on that particular bus shall get affected and shall stop supplying the load. In such cases the bus tie breaker plays a vital role of feeding the load through the live remaining bus and interrup ...

#### Why different countries have different voltage?

##### Friday, May 20, 2016

Why voltage in some countries is 220V (208V, 230V, 240V) and 110V (100V, 120V) in some countries? Why can't we have the same Voltage and what are the Pros & Cons of using 110 V or 220 V in their Respective regions?

110V or 220V, Each system has its own advantages and disadvantages, so each country before designing a system Engineers sat down agreed on factors and concluded on which system to use taking in account:
Their ...

#### Something about 120v 60Hz US, 240v 50Hz UK

##### Tuesday, February 9, 2016

The people have described the single phase 120/240v system that is used in the USA, Canada, and Mexico, with the center-taped transformer. Japan uses a similar system but the voltage is lower: 100/200v. Most North America appliances work in Japan. Commercial and industrial systems in the USA run on three phase 208Y/120v or 480Y/277v. Canada uses higher voltage, typically 600/347v. These are all 60 Hz frequency.

Most of the rest of the worl ...

#### Why we use 115v 400Hz power supply in aircraft?

##### Saturday, January 30, 2016

Aircraft electrical components operate on many different voltages both AC and DC. However, most of the aircraft systems use 115 volts AC at 400 hertz or 28 volts DC. 26 volts AC is also used in some aircraft for lighting purposes, where the power is generated by a commutator which regulates the output voltage of 28 volts DC. AC power, normally at a phase voltage of 115V, is generated by an alternator, g ...

#### Is US 120v or 240v?

##### Tuesday, January 26, 2016

Someone told me the appliances for United States 240v, are combined with TWO 120v hot wires, a neutral, and a ground wire, like refrigerator? If yes, can it be power by one 240v hot wire (single phase), and neutral, ground wire?

There are very few appliances in the US that are 240v, most are 120V, with only the high current ones such as a dryer, stove/range, and some air conditioners. However it is unwise to assume that all 240v appliances only utilize 240v, many older units utiliz ...

#### Solved the Noise on Tape Recorder Caused by Frequency Converter

##### Friday, January 22, 2016

Case: I am restoring a 1960s analog audio tape recorder for high quality audio use, the tape recorder is a USA model operating on 120VAC at 60Hz, the mains voltage in Singapore where the machine will be operated is 230VAC but 50Hz. Other converters that convert 230VAC/50Hz to 120VAC/60Hz have been unsuitable -- I hear high distortion and square wave noise to break through in to the audio i ...

#### Relationship between grid frequency and load in power system

##### Thursday, December 17, 2015

Higher output power of generator (hundreds of MWs) has bigger impact on the system frequencies than low power generators, because of its massive spin momentum (torque). The active (R) load acts directly on generator speed because it creates strong magnetic field in stator that is perpendicular rotor's spinning magnetic field thus forcing an opposite momentum(torque) which slows down the turbine, this is fixed with a speed governor which controls turbine speed by manipulating its spin momentum ...

#### The purpose of insulated bearing for Motors with VFD

##### Wednesday, December 9, 2015

There are 2 different scenarios that occur. One is a circulating current that can occur, mostly through the fact that the rotor is not perfectly formed (you can think of it as not being perfectly round) which creates a circulating current. Insulating one bearing will stop this circulation. The second scenario occurs when a motor is on a VFD (variable frequency drive) and especially a PWM VFD. This produces a charge on the rotor which wants to discharge, and the easiest path is almost always t ...

#### 50Hz or 60Hz? Keep the same V/Hz ratio

##### Wednesday, October 7, 2015

Failure to balance the V/Hz ratio with 400V/50Hz motors in the US, to accommodate for the widely varying voltage levels in all of the sectional grids across the country results in significant starting torque and HP losses. Variable Frequency Drives (VFDs) capable of full motor voltage/Hz/RPM/FLA levels are the very best option for use of these motor types.

The overall power grid across the US was created over 100 years ago, and though it has of course been expanded across the enti ...

#### LCI Drives vs VSI Drives

##### Sunday, September 13, 2015

An LCI drive is an old and different topology to a VSI AFE drive. The LCI drive has a long history and its advantages and limitations are well understood. It is simple and reliable, but requires careful attention to ac power system issues related to harmonic currents and reactive power. It also demands specially designed motors with low reactance, and must work with harmonic heating and air gap torque harmonics.

LCI drives have low input power factor, 0.5-0.92, especially at lower ...

#### Difference between Resonance and Natural Frequency

##### Saturday, August 29, 2015

If you have an electrical circuit consisting of a capacitor (capacitance C) and an inductive coil (inductance L) and you load the capacitor, you will observe a sin-wave oscillation in this circuit as soon as you remove the supply. Caused by the losses, the amplitude of the oscillation will decrease with every cycle. The frequency of the oscillation is the natural frequency of this circuit and is given by 2*π*f=1/sqrt(L*C).

If you connect a frequency variable supply (exciter) in ...

#### Does motor output constant power at 50Hz and 60Hz?

##### Saturday, August 8, 2015

I require urgently 75 hp motor which should be compactible for both 50Hz/60Hz, I'm very much confused as frequency changes speed will change but I'm wondering how the power rating of the motor remain same in practical power must vary but manufacturer claims power remains constant? Is it possible?

A: It is possible for a motor to deliver the same power output at 50Hz ...

#### Why motor, generator and transformer are designed for 50Hz or 60Hz?

##### Monday, July 27, 2015

In very general terms the silicon-iron magnetic cores of motors, generators, and transformers get smaller as the frequency they operate at gets higher. This of course assuming the energy delivered at the output of both cases is the same. Because of this, when you have 50 Hz core in a motor, generator or transformer, this core will generally bigger and heavier (more silicon-iron). This is because it needs to have more magnetic mass in order to be able to accommodate the extra volume of magneti ...

#### Why isolation transformer is used at the output of online UPS?

##### Saturday, July 25, 2015

An isolation transformer is a transformer used to transfer electrical power from a source of alternating current (AC) power to some equipment or device while isolating the powered device from the power source, usually for safety reasons.

What this means in reality is that a normal application for an isolation transformer is to either keep the load from generating harmful harmonics back onto the distribution bus ...