480 Volt - 3 Phase Motors and Heaters Running on 415 volt - 3 phase Ok?

[JNiehaus - Electrician]

I have a cold weather package I need to setup for 4 1250 kw generators we have on site. These are derated currently to 415 volt, if I tap off the busses to run my 480 volt winter package will this damage the motors or heaters?

I have two pumps and two inline heaters for a total of 45.15 amps protected with a 60 amp circuit breaker on the back of each generator.

Just need to know if 415 is acceptable or if I should bring in a generator to cover the load at the proper voltage.

Thanks,

Justin

 

[itsmoked]

Too many variables for the little info provided to make any statement.

What do you mean "derated"? Someone decided to use the wrong voltage? (not gonna fly)
Or are these 60HZ generators going into 50Hz service? (probably fly)

The heaters don't care about the frequency but they will care about the voltage difference. The power the heaters put out will drop with the square of the voltage change which means a lot less power. Too much less? Depends on what the actual ambient can get down to. Realize that with global weather screwed up it could be a bit colder than any one has seen at the location before. So is it arctic, mild, tropical?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[JNiehaus - Electrician]

The main generators the system is ssetup to heat have been derated from 480 to 415 to provide 162 240 volt plugs to a seacan without needing a transformer. So currently if I run off the bus of another generator it will come in as 415 not the 480 that is called for.

They are all 60 hz.

This is a setup in northern alberta where it can hit -45 Celsius.

 

[davidbeach]

The motors won't like it at all and the heaters will be warmers, not heaters.

 

[JNiehaus - Electrician]

Figured as much just arguing with the bosses that dont want to spend the money

 

[waross]

Your motors will have about 75% of the 480 Volt torque.
Starting the motors may be easy or it may be difficult.
It depends.
The pumps may overload the motors.
It depends.
Your heaters will put out about 75% of rated heat.

Auto-transformers will be a lot cheaper than generators.
You have 5 MegaWatts and you want to power some packages at a little over 4 kW ?

You may use three 240V to 36 V transformers in a wye connected autotransformer configuration.
They will boost your 240 volts up to 276 Volts.
That will give you an output of 478 Volts.
That will be fine for your 460 Volt rated motors (check the nameplates).

Transformer sizing:
The 36 Volt windings must carry the load current of 45.15 Amps.
36 V x 41.15 A = 1494 Volt-Amps, or 1.1494 KVA.
So, you need three 1.5 KVA transformers.
Good luck finding a generator at that price.

You could also use a two transformer auto-transformer boost, but sourcing suitable voltages may be an issue.
The two transformer solution is the "go to" solution for conversions either way between 480 Volts and 600 Volts.
A 480 Volt to 120 Volt is a natural.
Transforming fro 415 Volts to 480 Volts with an open delta requires a non-standard voltage.

Some of the major plants around Fort Mac. are 600 Volts, some are 480 Volts.
During turn-arounds there are a lot of auto-transformers in use.
1. A 600 Volt plant rents 480 Volt equipment for the turn-around.
Auto transformers will drop the 600 Volts to 480 Volts to power the rental equipment.
2. A 600 Volt plant rents 480 Volt generators for temp power for a turn-around.
Auto-transformers will boost the 480 Volts up to 600 Volts.
3. A 600 Volt plant had their own temporary lighting equipment including 600 to 120 Volt transformers.
During a major turn-around, the power was off and 480 Volt generators were brought in to power the temporary lighting equipment.
This of course needed 480 Volt to 600 Volt auto-transformers.
Then they rented some exhaust fans that were only available in 480 Volts.
A second set of auto-transformers was brought in to drop the 600 Volts back down to 480 Volts.
Don't be afraid to use auto-transformers to change voltages in Alberta.
It is done frequently.
Is your site accessible by road?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[JNiehaus - Electrician]

Yeah that could be a possibilty but this site is a bitcoin mine completely powered by generators. If these generators all go down because of a gas problem will not be able to start again without running the winter package. I had two not start yesterday at 5 degrees Until I did a temporary hookup as I stated. These generators go down ALL the time.

My plan was to get a 125 KW 480 volt 3 phase natural gas generator with a backup propane option in case the plant goes down. That way all 4 generators can be heated if anything goes wrong. Every minute counts with these bitcoin operations.

Im currently planning to parallel two and maximize the other two so there wont be room to be powering these systems as well. they will be at 90-95% load and I do not want to push it.

So basically I want to bypass them with a backup generator. I just wanted to confirm what the change would be with the 415, so I could bring it to them.

 

[waross]

The change may be as simple as a few degrees turn of an adjustment on the AVR.
Consider paralleling three sets at 60-65% load. Then if one goes down the system doesn't go down.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[edison123]

"I have two pumps and two inline heaters for a total of 45.15 amps protected with a 60 amp circuit breaker on the back of each generator."

You are looking at roughly 40 KW for heaters and motors. It is much easier and a whole lot cheaper to replace your 480 V rated heaters and motors (along with higher capacity supply cables, if required) with 415 V rated heaters and motors for the same KW capacities.

Muthu

http://www.edison.co.in

 

[jraef]

What frequency are the 415V generators? If they are 50Hz, the 460V motors will be fine and provide full torque, although they will run 20% slower.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[LittleInch]

Did you say a "bit coin mine" ???

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[itsmoked]

Yeah he did. What a tragic waste of energy and pollution generation the world has concocted.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

They are running 240/416 Volts, 60 Hz to service 240 Volt servers.
A significant part of the cost of Bit-Coin mining is the cost of energy.
Buying raw gas at the well head to run generators is a cheap source of energy.
A miner in southern Alberta doing this claims to be the world's largest Bit-Coin mine.
The latest thing in Bit-Coin mining is using flare gas to power containerized units.
Many oil wells produce some gas along with the liquid hydro-carbons.
It is not economically feasible to harvest this gas, so it is burned or flared, on site.
Flare gas is waste energy and a source of pollution.
Running on flare gas is almost free energy that would be polluting even if it was not used.

I have two pumps and two inline heaters

Check the nameplates.
The motors may be rated for 208-230:460 Volts, or 200-230:460 Volts.
Either one will run fine on 415 Volts.
Heaters?
Add one more heater to each package.
On the other hand;
Myself and others have been adjusting voltages with auto-transformers for years.
Myself for about 40 years.
It is the cheapest and easiest solution to voltage mismatches.
In special circumstances I have done 600V to 480V to 600 V.
I have seen others do 480V to 600V to 480V.
In this case adding 36 Volts to 415 Volts is a ratio of about 11.5 to 1.
The KVA capacity of a bank of auto-transformers will be about 1/11.5:1 of the KVA capacity of a conventional transformer bank.
Don't they teach this anymore?

But I think that we may be missing the point of this thread.
I get the strong feeling that the OP does not want a cheap, easy solution.
He wants to build a case for a new, dedicated, generator.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[waross]

Some comments:

These generators go down ALL the time.

That is not normal for generators.
It strongly suggests some variation in gas quality.
If you are at one of the newer mines burning flare gas, even more so.

I had two not start yesterday at 5 degrees Until I did a temporary hookup as I stated.

It may be preferable for your standby set to use an alternate fuel.
If a slug of unsuitable gas takes out your generators, then starting the standby set on the same fuel supply may be problematic.

A plan to ponder:
Use an N+1 system.
Always have one more generator online than your operation needs.
One set going down will not shut down any servers.
Compare the fuel consumption with the same load spread across two sets versus spread across three sets.
The difference may be less than you expect.
Than express the extra fuel cost for a year in minutes of down time avoided.
Come off your bus to feed an auto-transformer stepping up to 480 Volts.
The 480 Volts will go to an Automatic Transfer Switch (ATS).
From the ATS go to a splitter and then to your packages.
Note, use N+1 for your main loads. The cold weather packages may be extra and need not counted in the N+1 scheme.
If the package load does slightly overload the prime rated sets, the package loads are small enough to be allowed under the occasional overload rating of the prime sets for the length of time it takes to get another set back online.
I hope that these are prime rated sets. If not, re-rate them as prime sets.
Add a standby diesel generator feeding to the ATS.

Operation:
Normally, the packages will be powered by your main generators.
In the event of the total failure of the main bus, the diesel generator will start and come on-line typically in less than 10 seconds.
Why diesel?
There are many more persons familiar with diesel engines than with propane powered sets.
The sets are available completely self contained, including fuel tanks.
There is always diesel fuel available even if it is siphoned out of vehicle fuel tanks.


Bill
--------------------
"Why not the best?"
Jimmy Carter