45kw motor and generator problem

[davesparks]

I agree the MCb is the problem, but harder to intigrate RCD protection with an mCCB

I have been down turned up the star delta change over time, helped a bit, but he said it also tripped once mid ride, far from ideal. So reluctant to keep the C125, measured it with my clamp meter with max function and it peaked at 175A, also measured earth leakage, it was around 30mA until the motor was started, meter maxed out then dropped to 120mA while motor was running, but I'm unsure if he meter would accurately read when the motor starts as there's such a high inrush. The next question is the RCD time delayed, I don't know it doesn't say type S. See picture this is what they have at the moment, as you can see not easy to fit anything other than this set up. This box supplies a 63A, 2x 16A and 32A. There is an main RCD on the generator but have this turned off as a fault in one ride cannot shut the whole lot down when they are open.

I'm not sure what to suggest.

It's not too hard to integrate earth leakage protection into an MCCB, just fit a shunt trip operated by an earth leakage relay.

How does the generator behave when the mcb trips? Does it throw up any faults, lose speed, send up a cloud of black smoke etc?

Switching out the main RCD on the generator may not be a very sensible idea, and may not be compliant with the requirements of bs7909. You should adjust the tripping current and time delay in order to achieve discrimination.

 

[Rocboni]

You would also need to Integrate CT coil and earth leaks the relay as well as the MCcb, and there is no extra space.

The generator does noticeably change speed when the motor changes over but no smoke

The generator came from an sound and lighting company so I would imagine it implies with bs7909

So the trip during mid ride occurred when the motor was up to speed not during the transition to delta.

Apparently it did once but I am notsurprised as I have measured peaks of 175A for a few seconds.

The particular ride is a Miami,they are notoriously had to drive as the motor is subject to high load then very little very frequently.

 

[Andy-1960]

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

 

[westward10]

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

 

[davesparks]

You would also need to Integrate CT coil and earth leaks the relay as well as the MCcb, and there is no extra space.

The generator does noticeably change speed when the motor changes over but no smoke

The generator came from an sound and lighting company so I would imagine it implies with bs7909



Apparently it did once but I am notsurprised as I have measured peaks of 175A for a few seconds.

The particular ride is a Miami,they are notoriously had to drive as the motor is subject to high load then very little very frequently.

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?

 

[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.