45kw motor and generator problem

[Rocboni]

Still don't seem to know what protection curve the MCB is....

See pitcture

When did you measure these peaks during change over or when it was up and running.

When up and running, it wasn't this high when changing over,

The generator cannot comply with bs7909 on its own! Bs7909 is the standard which covers your whole installation from generator through to the ride.

If the generator is noticeably slowing down then the output voltage and frequency will also dropping, this will have a knock on effect on everything it is powering.
Are you running this whilst other loads are on the generator, or is it the only load?

I admit i am not familiar with the standard but all the leads over 32A are covered by 300ma RCD and correct overcutrent protective devises and anything under this 30mA double pole rcbo, I'm sure there is more to it, it's not somign I am involved with every day, just been asked to look at this for them.

The voltage and frequency do not change, there are meters on the machine so you can watch them while transferring.

There are other loads about another 75 amps/ phase on at the same time.

 

[westward10]

Those measurements are more than double its expected flc and it sounds like the other loads are also contributing. Sounds like this new generator maybe inadequate for the expected loading.

 

[Rocboni]

It all used to run off a 200kva with no issues, this was captured by my clamp meter with the max function it may have only existed for a second, the whole ride with motor running but no load (lights ect) was only drawing about 50amps/phase.

It has been designed to run off a 125A socket from day one, the machine itself has a 160Amp Mccb albeit someone has fiddled with it and turned it up to its max, the adjustment screw is chewed to bits.

 

[davesparks]

The voltage and frequency do not change, there are meters on the machine so you can watch them while transferring.

There are other loads about another 75 amps/ phase on at the same time.

[]

You said the generator slowed down, but you are also saying that the voltage and frequency do not change. This is not possible, The frequency is governed by the generator speed, if one drops then the other must.
Also when you apply or remove a load on a generator it has to react to compensate, the speed and frequency will change. How big a change this is will depend on the magnitude of the change in load.

 

[Rocboni]

I was wrong to say it slowed down, you could tell it Was working harder but it was coping fine, it drives the machine easily

 

[westward10]

Is it possible to ditch the ancillary loads and just run the motor.

 

[Rocboni]

Do you mean the lighting on that ride or the other loads on the generator, the other main loads are run from other plugs with their own protection all of which are fine, it's just when the motor changes to delta and the very odd time while the ride is operating, I am confident the generation is well capable of driving it, as well as other rides at the same time.

 

[westward10]

Yes ignore my last post I misthought the ancillary loads were affecting the motor load. I think the mcb tripping on the delta transition is down to the fact it is an mcb. Tripping when it is running could be down to a number of factors such as poor maintenance placing additional loading on the motor through poor lubrication, worn bearings etc.. Is the passenger capacity being exceeded.

 

[Rocboni]

So you don't think changing to a D curve would make a difference?

You cannot really exceed the ride capacity as there are a fixed number of seats. There is also counter weights to off set the "boat" so I can't see where the load is really.

 

[westward10]

It may do but it also sounds like is is prone to an overcurrent issue and changing the type may not resolve it.

 

[Rocboni]

Trouble is it's £250 to find out.

 

[westward10]

Think you need to explain to the owner this and that there is no guarantees it will resolve it. Why did they replace the old generator.

 

[Rocboni]

I will do, this is a vast improvement in terms of protection on the usual set up, the sockets are usually straight onto the bus bars of the generators and the older ones don't have RCDs built in! So this is all quite hard to explain and hard to get them to understand why you need all this.

They will also want suggestions how to overcome this but there's space to fit a Mccb.

How would you normally supply this size of motor?

 

[westward10]

BS88 fuses or a suitable mccb.

 

[Rocboni]

The motor is actually supplied buy 2x 100 A and an 80amp bs88 fuses (not ideal) before the star/delta contractors and these are holding up, by the looks of it the 80amp is an original.

 

[westward10]

The mcb I feel is the Achilles heel as they are not suitable for large size motor protection.

 

[Cadgey123]

The motor is actually supplied buy 2x 100 A and an 80amp bs88 fuses (not ideal) before the star/delta contractors and these are holding up, by the looks of it the 80amp is an original.

Link the MCB out the equation to see what happens?...

You said you had added protection in regards to the other fuses.

 

[Rocboni]

They have fitted a 4 pole isolator at the moment so that can operate, but ther is no protection for the cable and socket other than the MCcb in the generator with is about 400Amps

 

[westward10]

Link the MCB out the equation to see what happens?...

You said you had added protection in regards to the other fuses.

Link out the mcb is just removing the problem not solving it plus you remove circuit protection for the socket.

 

[davesparks]

what is the overload trip on the starter doing during all of this? Assuming it is set correctly then that should be providing the overload protection so the mcb or whatever will only be needed for fault protection.