Motor Starter for 250 KW 3 Phase Induction Motor

So you don't want to use a soft starter or a VFD or a star/delta , what's left?

Rotor resistance starter

stator resistance starter

auto-transformer starter

Check this link to see if anything appeals to you....

https://www.c3controls.com/starter-basics/

What is the application?

https://www.se.com/ww/en/product-category/3000-motor-starters-and-protection-components/

Please define <...best...>?

Its a circular saw 250 kw motor with blades upto 3000 kg.. this motor is used for rotating the blades used for cutting the granite blocks.. since my vfd igbt are faulty and no spare are available due to the corona virus lock down... i am trying for the spares but during that time i need to run the machine so i plan to make a start delta starter with limiting the starting current to a low value as much as possible.

<...limiting the starting current to a low value as much as possible...>

At the moment of energising, the current will be the applied voltage divided by the terminal impedance. It doesn't matter to what the motor is connected as this value will always be the same figure. How long it takes to reduce is dependent upon the rotational inertia of the motor/load combination. For a large circular saw, this value will be higher than, oh, say a small centrifugal pump.

<...star delta...> is used traditionally for circular saws. In the absence of other equipment during the <...corona virus lock down...>, it's probably the <...best...> one can do.

Like all motors there needs to be an overload protection device as well as fuses to protect the cables. Additional protection could be given in principle by having a temperature trip driven by a detector in the windings, subject to motor design and prior provision having been made for it, though this is a refinement; it could well be that this arrangement couldn't be provided in the circumstances, in which case it is essential to set the full load current trip setting on the overload protection device to the same figure on the motor name plate for whatever voltage the motor is to run at in <...delta...>.

Co-ordination protocols between fuses and overload device are provided in national standards. In the UK, British Standard 7671 would apply, for example, and this standard also covers cable sizing protocols.

When ordering <...spare...> parts, make sure some surplus are held in stock once the replacements have been fitted and the thing is working, because it sounds as though not having any is a false economy.

If you have a local qualified repair facility they may be able to repair the drive.

There may be some within shipping distance within your country,do a google search for them.

Usually only a few components fail,unless it is a catastrophic failure,such as over voltage or lightning strike.

Normally on these drives,a capacitor fails on the gate circuit that feeds the IGFET,causing a gate failure due to the gate trigger being applied to rapidly.

In this case,the IGFET and capacitor must be replaced.

The discrete components are relatively cheap,labor is not.

Quaiser,

As I said in the other question you posted, apparently to the same motor, starter, and application, we need more information. Otherwise, there is no way we can give you a good answer!!!

1. Is there one blade or more than one blade?
2. Is the total mass of the blade(s) 3000 Kg as you stated? (That's pretty big.)
3. What is the inertia of the driven load?
4. Do the blade(s) run at motor shaft speed or is there a reducing gear box?
5. If a reducing gear box, what is the ratio?
6. Has the 250kW motor started this load in the past?
7. If so, what was the inrush current and how long before the saw blad(e) got up to full speed?
8. How long has the existing Yaskawa drive been doing this job?
9. What are the parameters (yes, all of them)?
10. Did the failure occur during starting or during running?

What is the thickness of the granite being cut? (A curiosity question, as I remember seeing an old limestone quarry that had a jig to make multiple simultaneous cuts in blocks that were over 6-feet [2 m] in thickness.) At one time I had to supply power to a high-inertia load, a fan on a 200-hp motor which took about 90 seconds to get up to speed; at another time a co-worker had to repair a DC motor starter for a log chipper (the chipper's wheel was 2m diameter and about 30cm thick).

In my opinion, you need to answer the questions or get off the blog site. Without a LOT of information there is no way we can give you decent advice.

--JMM

You could use smaller current IGBT of the correct voltage rating and parallel them up with balancing resistors to obtain the current rating until the correct replacements become available.

Used this very system on an oil rig and the work around was operating flawlessly until the correct items could be imported and were left in until it became convenient to exchange. The work around was kept on the shelf as well as a spare set for replacement.

The solution does rather depend upon the characteristics of whatever the motor is turning, which have been withheld from the forum.

Please explain what <...more added protection...> is intended to mean?

Please describe the motor manufacturer's recommendations and why these cannot be provided within the <...vfd...>?

https://cr4.globalspec.com/thread/134346/Yaskawa-a-1000-250-kw-Drive

Two questions please:

1. Why are you ruling out the two most obvious methods, soft starter and VFD?

2. If motor protection is your goal, use a thermal overload, its a code requirement anyway!

GE Multilin 369 is a popular motor protection relay, it is used with your star delta contactor set, potential transformers and current transformers, motor RTDs or temperature switches or provides full protection for your motor, including rotor protection. Or Eaton EMR5000, or Multilin M60 may be more appropriate for this size motor, smaller but critical.

Sir,

1. What is the voltage level being envisaged ? Is it 415 V ? If it is higher voltage then Stardelta,SS are not required. VFD's are costlier proposition ,to be considered only if there is a process requirement,hence not being considered.

2. If it is 415 V,then wld like to know the LT switchgear configuration...What is the base load, When this particular motor has to start ...with that maybe u will b able to decide whether star delta or SS is to be used.

3. There is also commercial angle. SS will be costlier than Stardelta. VFD's are much costlier.

4. From maintenance point of view Stardelta starter is a bit troublesome and requires maintenance..

5. SS should be a viable option.

Regds

There are different Starters for 3-phase induction motor to start like -

1. Star-delta Starter

2. Auto transformer starter

3. Direct on line starter

4. Rotor resistance starter ( used for slip-ring motors )

Reference - Starting of 3-Phase Induction Motor