When considering fault current levels, line to line faults are considered, not line to ground faults.
If system upgrades increase the level of available line to line fault currents, then reducing line to ground fault currents does nothing to help.
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...
