Fairford synergy soft start unit

[Rocboni]

Thanks Rob, The duty cycle isn't that high maybe 5 starts per hour, The Soft start has facility for PTC termistor input so i'll go with 125A fuses.

 

[marconi]

What type of 125A fuse? Why go up from 100A BS88 to 125A type? when the Synergy motor start is softer than previous star-delta? Has start-stop regime changed to something more onerous/frequent? Is cabling suitable?

 

[Bobster]

What type of 125A fuse? Why go up from 100A BS88 to 125A type? when the Synergy motor start is softer than previous star-delta? Has start-stop regime changed to something more onerous/frequent? Is cabling suitable?

BS88 fuses can't react under a fault quick enough to protect the electronics inside the soft start.

Semi conductor fuses or type J can protect them, however due to them being able to react so fast, they also can suffer more from nuisance tripping if the circuit is under a high start duty.

 

[Rocboni]

Going to go with 3 x

Ferraz Shawmutt - 125A High Speed URD 22 x 58mm Semiconductor Fuse
621 CP URD 22.58 125 (A 220708)

 

[Rocboni]

No need to follow UL requirements as I presume this work is stopping within the UK?

UL have some funny workings, probably not worth me explaining as I don't think you do work in the US (correct me if I'm wrong an I'll explain) there's no need to have the circuit breaker and the semi conductor fuses.

I just copied and pasted from the datasheet, no I don’t do work in the US, in a previous life I used to do a fair bit of product design, most of which eventually went on to be sold in the US so it involved having our products UL approved, it was an absolute nightmare getting the stuff through!

 

[marconi]

Thank you.

 

[Rocboni]

PROBLEM! Having built the panel I got round to connecting it up today, on starting the motor it started fine but then I got a line failure fault, long story short it has eaten its way through 6x 100A semiconductor fuses due to starting current. The 125A fuses had a 6 week lead time and I had to take 10 at the Costner of around £400, I am reluctant to buy these as I think they may blow aswell, starting to see why maybe they state 250A. I have successfully had 45kw motors run on 80A BS88 just fine (star delta starter)

Any suggestions? I could do without having to upgrade the panel sizes, I have 25mm tri rated feeding a main contactor 55kw then 10mm tri rated to soft start and motor terminals (wired inside delta)

The whole panel is running from a 50mm 4 core with 125A motor rated fuses (these have been fine) I’m tempted to try some standard motor rated fused just to get it running.

 

[Bobster]

What do you mean by a line failure fault? Is this a fault code given on the soft start?

Try with normal fuses if you like, however if there is an actual fault, they will not blow fast enough to protect the thyristor stacks in the SS>

 

[Rocboni]

Yes it’s a fault code given by the soft start and drops out the line contactor on phase failure.

Rob I understand this, I wasn’t thinking of a long term solution however I can’t see anyway round it without upgrading to much larger fuse.

I would prefer a mccb tbh.

 

[netblindpaul]

Rob, the OP has 4 off Pilz safety relays in the panel, and a single point of failure for the motor contactor, I'm surprised you haven't queried that yet?
I have to say though, I've seen a LOT worse panels from companies who are supposedly experts at panel building. A very good job.

OP: I would make sure that you do your 13849 analysis and validations though to make sure that you meet the PLr for the hazards.
A single monitored contactor, may, not be enough. If it's monitored which it seems to be, then make sure that it's force guided, along with the auxiliaries, and that they are direct acting, and mechanically linked to the main contacts.
Oh and remember clause 13.1.1 in EN 60204-1 with regard to cable entries into the top of enclosures...
It's not worded like that, but if you read it, you should see what I mean.

 

[Rocboni]

Believe me this is a vast improvement of safety than previous panels designed by the manager. The single motor contactor and soft start operates a totally enclosed positive displacement blower a single contactor is adequate it poses virtually no hazards

 

[Rocboni]

Think I might have been a bit thick, the starting current limit is set at it’s default of 3.5 or 350% FLC, i will reduce this and see what happens, the only worry is that the pump can be quite hard to start so it might trip however you can switch start current limit trip off. There are all sorts of setting such as kick starts

 

[netblindpaul]

OP, If there are no hazards, why the Pilz safety relays, they are not cheap, so you could have saved an awful lot of money there, in the relays and the integration of them?

 

[Rocboni]

There are conveyors and elevators with inspection doors, e stops etc.

 

[netblindpaul]

OK, so there are hazards then & ISO 13850 requires PLc against ISO 13849.
This is a new control system, thus it requires a DoI, and the completed system a DoC.
So you need to validate against ISO 13849, and you need to be able to provide a Technical File if requested.
Conveyors probably have their own HD, depending on the elevators, they probably will also.