Note that this case applies when the transformer is the same capacity as the alternator.
For a transformer of 1/2 the capacity of the generator I suggest using rated current times two, plus or minus 25%.
For a transformer of 1/3 the capacity of the generator I suggest using rated current times...
Take the rated KVA times 1000.
Divide by the rated secondary voltage to get the rated secondary current.
The rated secondary current must be equal to or greater tha the losd current.
Example:
Transformer Ratings.
10 KVA, 480/120 Volts
10,000 VA / 120 Volts = 83.3 Amps.
The 120 Volt windinhs...
As I understand the rules, fault currents are based on line to line faults, not line to ground or line to neutral faults.
If they are impedance grounding distribution circuits I hope that the services do not include a neutral conductor.
The last time I saw impedance grounding it was on the power...
You may find it educational to read other posts before posting.
A number of your suggestions may be a little off.
One instance;
By far the cheapest, both cost of material and labour, is the open delta auto-transformer boost.
Capacity depends on KVA, not kW.
This connection inherently causes a...
I would size the protection to withstand a very short transient of 25 times full load current and sleep well.
But, that is for a grid tied system.
For an islanded system you may wish to consider the following points:
Your energizations per week or year may be many times what a large grid...
Consider an induction coil or a transformer.
A rising current in an induction coil, a transformer coil or in a motor winding causes a rising magnetic field. That rising magnetic field induces a voltage in the winding that is causing the magnetic field.
In a motor, part of the magnetic field is...
I once set up a demonstration for some students in a vocational school shop.
A three phase induction motor coupled to a DC motor.
I connected a resistor bank in parallel with the AC motor.
I started the AC motor on the normal supply.
Then I ran up the DC motor until it was over-speeding the AC...
A question and a suggestion Jeff.
Can they use the water to spin up the turbine or is there an issue with flow control?
Suggestion; I am wondering if even a small excitation will boot-strap the motor and cause it to start self exciting?
Will the VFD pick up the motor on the fly?
In a synchronous motor the speed is fixed.
The back EMF voltage is controlled by the excitation.
At lower levels of excitation and back EMF voltage, the motor draws reactive power.
As the excitation is raised, the back EMF rises until it equals the supply voltage.
At this level there is no...
Typically, full load = 1760/1800 = 40 RPM slip = 40RPM/1800RPM x 100 = 2.2%
You are on the wrong track considering voltage.
Voltage differences drive reactive current.
Normally, the phase angle of the back EMF decreases as the motor speed increases.
Phase angle difference is what drives the...
Did I get this right:
This is a self supporting span, but the capacity is increased by the addition of cable stays?
I wouldn't want to be tasked with evaluating deterioration and suitability for continued service 40 years or more from now.
Please tell me that I have misunderstood something.
Rental companies supplying the oil industry in Western Canada have both open delta and full wye autotransformers available for rent.
Many petro-chemical plants have 600 Volt systems. Almost all rental generators are 480 Volts.
When a 600 Volt plant needs temporary power, they rent a 480 volt to...
Thank you for the thank you.
Anecdotally when I worked for a contractor in Western Canada, we had a customer with a 480 Volt service.
In Eastern Canada they had a similar plant with a 600 Volt service.
They would frequently sent 600 Volt equipment out west and it was my job to spec and plan the...
Fun with numbers:
Boost 380 Volts to 490 Volts.
What transformer capacity is needed for a 50 Amp load?
Three phase transformer: 50 A x 490 V x 1.73 / 1000 = 42.4 KVA x one transformer
Three single phase transformers: 50 A x 283 V / 1000 = 14.15 KVA x three transformers.
Two auto-transformers...
Read my bLIPs;
Pit falls:
Volts per Hertz.
380 Volts suggests 50 Hz.
60 Hz transformers used on 50 Hz must have the maximum allowable voltage reduced in the ratio of 50Hz/60Hz to avoid magnetic saturation.
With a maximum voltage of 575 Volts you may consider limiting 50 Hz voltage to 489...
