Advantages On Star-Delta & DOL Connection On 3-Phase Submerssible Pumps.

The supply voltage and the motor voltage are incompatible.

Hello! Sir, I'm very sorry regarding my submerssible pump specification, regarding the Voltage rating: I review the nameplate rating, It is Star = 660Volts and Delta = 380Volts. I'm very much wrong. That's why I wonder how come specification goes like this. It will come out there are two separate windings in motor. I'm very sorry for this.

Why do you think there are 2 separate windings? 660v star, 380v delta is just what to expect, as various posters have said.

Codey

I am not sure why he feels a 380/600 volt rated motor is not compatible with a 380 volt supply but I see no problem with it.

As far as direct line starting that will depend on how much capacity your supply power source has and if it can support the full start up load with out too much of a voltage drop.

If it cant do a direct 380 to 380 volt start up you still have the possible option of setting up the motor to start out on the 600 volt connection while being fed from the 380 volt source. That will in effect give a basic soft start ability to a limited degree but an additional system of contactors and timing controls would be needed to make the 600 back to 380 volt connection on the motor possible while its on the go at speed.

The only other option if the power source cannot support a direct line start is using a VFD unit to bring the motor up to speed slower and while limiting the starting current.

Something is not right here. In a dual voltage Star-Delta motor winding arrangement, the difference is always a factor of 1.732 (the sq.rt. of 3) and the Star connection is always for the higher voltage. So either your motor is 347 Delta / 600 Star, or it is 380V Delta / 660V Star.

Either way, the starting method has everything to do with your goals; basic Reduced Voltage starting, in whatever form, is used primarily when you have issues with the starting current causing too much of a voltage drop on the supply system feeding it. There are several ways of accomplishing this, one of them being Star-Delta in which the motor windings are connected in Star first, then run in a Delta connection. This has the effect of reducing the effective voltage across the windings during start-up by that sq. rt. of 3, so you end up with an effective voltage of 58% (1/1.732). Because motor torque is a product of the square of the voltage, you end up with 33% torque from the motor. If your load can accelerate to 90% speed with only 33% torque, then Star-Delta starting will work to reduce the peak starting current. But if it cannot, the starting current peak will STILL be just as high when you transition from Star to Delta, and in fact under the right circumstances, may even create a spike that exceeds 2000% FLC!

I prefer solid state soft starters over Star-Delta in all cases. The risks involved with S-D are too great.

Yes, tks for the idea Mr. JRaef. This is the first design connection star-delta starting. But the submerssible pumps arrived, as per specifications has 380Volts for star & 600Volts for delta. This can be connected in DOL starting by supplying 380Volts. What are any possible problems on this and is their anny suggestions to solve this problem? Tks.

Are you sure the nameplate indicates star 380 V and delta 600V ?

Does the motor nameplate does not indicate Delta 380V and Y 660 V

Can you tell us the nominal motor current in star en delta ?

When the nameplate says star 380 and delta 600V it would means you have a motor with two seperated windings, and this is very uncommon for a pump.

Hello neng

You need to read again what JRaef wrote. If the nameplate or instructions say 380v star, 600v delta, there's something badly wrong, the fact that they don't differ by a factor exactly √3 is a detail!

If it's wired for 380v delta, 660v star (which wouldn't be unusual) and your supply voltage is 380v, you can start it either DOL or star-delta. If your supply voltage is 660v, you can only start it DOL. Of course the DOL connection at the motor is different for the 2 cases. (that's just for the 2 basic starting methods, ignoring more sopphisticated types)

Cheers........Codey

i don think dol is the ideal method for this kinda load (90kw).....dol starting is used in small motors within 5kw....A DOL starter connects the motor terminals directly to the power supply. Hence, the motor is subjected to the full voltage of the power supply. Consequently, high starting current flows through the motor. Because of the in-rush current in motors, the starting currents will be 5 times that of normal current....so in your case don't even think about dol starting ...you can either go for star delta starters or soft starters........

Provided the electricity supplier is happy, there's no reason not to start it DOL. Worth checking with the pump manufacturer but very unlikely he will object.

As JRaef pointed out in #3, there can be bigger current spikes using star-delta.

Cheers.........Codey

With DOL the starting current will be 5 times the normal current....which means a large voltage drop across the distribution system....even star delta has problems but it s very much preferred over DOL.....DOL s cheap and r used below 7kw......star delta cant be used when load torque requirement s 50% more thn motor rated torque,else we can use it..........best solution s soft starters or vfds....check this link http://www05.abb.com/global/scot/scot209.nsf/veritydisplay/2985284834bcff7fc1256f3a00274038/$File/1SFC132002M0201.pdf

check out this link for more info

Star-delta cannot be used when starting torque is above 1/3 full-load torque, as that's the starting torque produced on star-delta.

In practice, most loads fall into one of 2 categories

1. e.g. centrifugal fans, pumps etc where torque varies as speed² so is zero at start, for which star-delta is OK.

2. e.g. conveyors, winches, positive displacement pumps or blowers etc where torque is constant and (nominally) = full-load torque. For these star-delta is no use unless the motor is oversized by a factor of 3. Even then the current is 6 x FLC (x 2 for star-delta, x 3 for motor size) so it doesn't help.

Need to ask the electricity supplier what his rules are for DOL starting. These can vary, no point in making assumptions.

Cheers...........Codey

ya i agree wit yo point......i too have mentioned the same point....even i don have any hard feelings for star delta......personally i don prefer it............but i prefer it over dol for larger loads bcoz of large currents and torque in dol...........if u use dol here , all the cables used will get screwed and it will give rise to insulation faults probably ending in destruction of the motor...................if we use star delta here the problem will be stalling.....if adjust the timer inside the star delta circuit in such a way tht it would switch to delta when stalling occurs then i think we can use star delta ......even stalling can cause hell lot of problems.....better go wit soft starters or vfds.................