Fairford synergy soft start unit

[Rocboni]

Looking at using a fairford synergy soft start unit as below to start a 45kw motor, just wondering what it means by connected in line, I’m presuming they mean star but can see how the motor would run correctly being 400/690v rated?

https://inverterdrive.com/file/Fairford-Synergy-Quick-Start-Guide-V03

I’m thinking it needs to be in Delta to get 400v across the windings.

It’s also asking for 250a mccb protection via an inverse time delay mccb, or alternatively use fuses.
Struggling to find a inverse time delay mccb but it would be my preferred method.

 

[marconi]

On page 9 of the reference there is a note which explains how a synergy soft starter of a lower current rating than the motor can be used provided that the motor windings are wired Delta and the synergy is wired into them as shown in diagram so that it controls the current through each winding rather than the current to a pair of windings.

When wired in-line (or in series) with the motor the synergy must be rated to control the full line motor current.

If your supply is 400V, then the motor windings must be wired for this line voltage - so yes in delta.

 

[marconi]

Circuit breakers which include a thermal overload functionality to detect overcurrent are inverse time delay types. The manufacturer advises the use of a UL marked mccb - UL is an American scheme - but UK manufacturers can supply suitable mccbs. See:

MCCB-UL 489 Listed Molded Case Circuit Breakers - https://www.omega.co.uk/pptst/TD_TS.html

The manufacturer advises the use of both an MCCB and a semiconductor fuse see note #2 page 17/20 to provide enhanced protection against damage to the power electronic components inside the synergy. Suitable 250A semiconductor fuses aree suggested. See:

http://www.cooperindustries.com/con.../Resources/Catalogs/bus-ele-cat-10506-hsf.pdf

and

Bussmann | Page 513 | Kempston Controls - https://www.kempstoncontrols.co.uk/m/bussmann/page/513

 

[Rocboni]

Marconi
Thanks for the reply, so when it says line it means series as in two windings in series (star) however I can get away with using a smaller soft start if wired in delta. I need to clarify the the trip class so I’ll leave this until I find out.

Back to the circuit protection, I don’t have a sufficient supply (only 160Amps) to use 250A mccb, the motor was running off 100A bs88 fuses (started via star/delta starter) and it was fine, can’t understand why they call for such a high rating.

 

[westward10]

250A is way over required for a 45kw motor, I see no harm in going below this. I see problems if you exceed the 250A but not reducing it.

 

[marconi]

Re your #4 - When wired 'in-line' that is in series with supply cable to the motor, the motor windings must be configured for 400V if the source of supply is 3 phase 400V. I assume for the motor you are dealing with that meant wiring the windings in Delta, since the same windings could be wired in Star configuration and energised by a line voltage of 400 x 1.73 = 692V.

 

[marconi]

Here is the contact number for Fairford Electronics Ltd:

Contact Us | Fairford™ Soft Starters - https://www.fairford.com/contact/

for you to seek some clarfication.

The sizes of the fuses and mccbs they recommend are for short-circuit protection of the Synergy soft-starter and are the maximum size for each of these short circuit protection devices taking into account the prospective short-circuit current. So, as Westward10 said they can be smaller sizes but not higher. Before you phone see if you can find out the pssc for your supply.

The Synergy has electronic functionality to monitor motor currents and detect overload/overcurrent and then trip; see page 15 ''motor overload 'cold'trip curves''.

 

[Rocboni]

I agree FLC is only 77Amp I was planning on a 100a mccb starting current should be relatively low with the soft start.

I have emailed fairfords for further advice.

The motor will be wired in the delta configuration however this has brought up more issues as the soft start is remote from the motor, I need an appropriate 6 pole isolator.

 

[marconi]

Something like this switch-disconnector could do the job of isolation and also switching off the motor in an emergency.

6 Pole Enclosed Isolators IP67 & IP65 --- Pennine Components - http://www.penninecomponents.co.uk/product.asp?P_ID=512

 

[Rocboni]

That’ll be fun connecing two 16mm swa into it, I’ll go for a steel version, hopefully it has plenty room inside.

125A 6 Pole Boxed Isolator - https://www.motorstarters.co.uk/en/125a-6-pole-boxed-isolator

 

[Rocboni]

Do you think it can be connected in delta and then 3 wires to the motor like you would connect a VFD?

 

[marconi]

Re #11: Yes, if you connect the motor ('it') in delta at the motor's terminals and then use the 'in-line' wiring method to connect it to the Synergy. You would then only require a 3 pole switch-disconnector.

 

[Bobster]

You need to work out what is meant by the terminology of placing a soft start inline and in delta (more often called inside delta). The motor could be wired in either star or delta, for both configurations of the soft start. Providing it is a 6 lead motor.

This will probably help you understand:

Soft start circuit: how does it differ among soft starters? - http://www.soft-starter.co/soft_start_circuit.html

It also explains why you get away with using a smaller soft start whilst inside delta.

Your mentor/senior person that you are working with should know this.

Edit: semi conductor fuses require a lot lower Zs to operate and operate a lot faster than normal fuses. They are installed to prevent damage to the thyristor stack in the soft start, they are not designed for over current protection. This will be provided by the soft start or if not, you will have to provide it by other means.

 

[Rocboni]

Rob,

Thanks that has cleared the motor configuration up, the motor will be connected in the "inside delta" configuration however i will keep the soft star specification at 45Kw this will allow for frequent starting of the blower up to trip class 30, so it should increase reliability for the sake of very little extra cost.

Im still not 100% on the circuit protection though, it states a 250A Semiconductor fuse (class aR) is that in addition to a UL Listed inverse-time delay circuit breaker

 

[Bobster]

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.

Just ensure that the thermal protection you're utilising disconnects all of the phases to the motor. Via hardwired interlocks or position within the install.

Edit:

As stated before, the maximum protection you can use is 250A, personally I'd probably stick 125A fuses and have done, but you mentioned a high duty cycle, so you may actually require the larger fuses to deal with the heat cycling.