i am repeating my question, 3 phase,415 volt,1000kva generator, maximum how much current / load can be connect

Answer 1

This is a 3Ø system, so kVA = kV x amps x √3.
1000 kVA ÷ .415 kV ÷ √3 = 1393 amps

I am repeating your original question below, and then will provide additional comments:

"I want to buy a generator for our company i want to know how to calculate current for 1000kva capacity generator. and also want to know control and protection are required for the same generator please explain"

If you are still trying to size the generator for your existing facility, you can use your historical electric bills to determine the actual "demand" of the building(s). Look at the bills for a kW or kVA value. (Not kWh or kVAh)

The "demand" represents the highest rate of consumption over the course of the month. It is generally the average rate over a 15 or 30 minute interval. If the demand is in kVA you're all set. That is the peak load of your facility and a generator of that size or slightly larger could serve your entire facility.

If the utility bills demand in kW, you need to first convert to kVA by assuming a power factor. (Drop me an e-mail and I can explain that part in greater detail).

One consideration when sizing a generator is the inrush of large motors or welders. Induction motors typically have a starting inrush of more than five times their running load. If you had one really large motor, the starting inrush might be too much for the 1000 kVA generator to handle without damage. For example a 500 kVA motor might look like 2500+ kVA of load for the first few seconds when it is started. This large inrush is so brief that it is not seen in the demand values measured by the utility.

Assuming this is a "back-up" generator, you need to use a transfer switch to isolate the equipment from the electric utility when the generator is in operation. The alternative is to work with the electric utility to design a relay protection scheme to safely operate your generator in parallel with the utility's distribution system.

The reason for the transfer switch is to disconnect your load from the electric utility. If the utility power goes out, and you power up the generator without a transfer switch, you will backfeed through the utility transformer and energize the distribution lines at high voltage. Your company could be found liable in the event someone is injured or killed by the backfed circuit. In addition, your generator will be trying to serve all the other customers in the neighborhood.

Based on the details and wording of your questions, I believe the safe and reliable installation of a 1000 kVA generator is beyond your capability. I recommend you contact a licensed electrician who has significant experience with medium to large sized commercial or industrial customers. You and your supervisors will be much happier with the installation.

Answer 2

OK - You have elaborated - At that voltage you will have about 2400 Amperes.

I = P/E You have a generator putting out about 1 million watts. Divide that by the voltage and you get the usable amperes at rated voltage.

Drop that to 380 3 phase Y would transformer. With loss through this you will have about 2352 amps. But the voltage has dropped from 415 to 380 so the amperes will go up. You will have about 2500 amps available at the output side of the transformer. Remember this is TOTAL amperes across all 3 legs of the windings.

Remember that The Power is ALWAYS equal to the VOltage X the Amperage. If one goes up the other goes down. That will NOT change.

Transformers are 98% efficient so you must calculate the initial loss through the primary transformet before you calculate the oiwer available for your main buss.

If you have 1000 KVA before the transformer you will have 980 KVA at the out side. At 380 V, 3 phase you will have 2578 Amps.

980,000VA/380V = 2578.94A

OK So far? For safety you have to derate the system by 20% to prevent overload and burnout of the Generator or transformer.

you have 2000 amps at 380 volts.
That is on your main buss in the master control panel.
You have a master breaker there feeling smaller buss lines. On each of these is one breaker per machine OR you can take sub feeder lines to sub panels throughout the factory. From these sub panels you can distribute 3 phase for motors and secondary panels for 110 or 200 single phase for lighting and hand tools.

This is so complex and I want to tell you so much. How about I go there and do it.

Answer 3

Generator 1000 Kva

Answer 4

The rated current is:
(remember 1000 kVA means 1000*1000 VA, so:)
i = 1000*1000/( sq(3)*415)= 1391.2 A

Answer 5

Your rated current is 1393 A. So for better life of trans. you should give a load around 95% 1393A max. As beyond that transformer will get overheat so life will be reduced for that you have to provide better cooling near trans. Transformers are designed to operate at full load but manufacturers specs may vary.

Answer 6

I recommend you split the load among the three phases - e.g. connect one third of the circuit breakers (by amperage) to each phase. Be sure to connect each as phase - neutral, not phase-phase. You CAN connect all to one phase, but this is going to lead to problems, e.g. excessive neutral current, which may have side effects.