Electrical Engineering Spec Gone Bad.

Usually the consultant along with the client does the inspection of any material (panel/DG set/transformer) etc at the vendor's factory. Once he is assured that the material is in line with the specs. he gives a dispatch clearance, in order to dispatch the material to site.

Has the dispatch clearance been obtained, in this case, from the consultant? Even, if the answer is no, you can still sue the consultant. I hope, consultant has given in writing, his approval for manufacturing of soft starters.

Regards,

PG

Stamped approvals have been given, order to proceed.

What is the operating voltage?

112KW = 150HP.

The FLA @0.8pf, 415V is 194A and 0.8pf, 380V is 212A.

What is the motor name plate voltage ?

Is it that you are trying to control at different voltage? Why should load draw larger current than FLA

The question is not how they derived the 112KW rating, rather there will be a rapid degradation of the motor if this FLA is maintained for a long time. What has gone wrong ? After all the current is 10% more than the rated.

600v is the system voltage. The pump manufacture I believe is running the motor in the service factor, or exceeding it.

P = √3VI CosΦ

112000 = √3 x 600 x I x 0.8 (assumed)

I = 134.75 A/η

Note I am talking about FLA and not the starting current on DOL.

@209A it is 174.η KW and even at name plate 190A it is 157.η KW electrical inputs

Now even if I take efficiencies of 0.9 (quite poor) it is

150A, (and 156KW / 141 KW other two cases)

Are you working with single phase motor at this voltage/power?

stndard motor should be suitable for +-6% .in India now all motors are made for +-10%.He should have ctered for 415-10% while designing the starter.

You're into the awkward realm where business and engineering clash. The key factor your company's upper management need to decide first is the value of this customer to your company. Now depending on how valuable this customer is to your company one of these scenarios will be decided by management:

• All efforts to rectify this design short coming will be paid by your company to keep this customer happy. Chalk up these losses as part of the learning experience in dealing with this golden client.
• Design up a more robust system that will handle the actual loading this customer has instead of the claimed loading. Offer this new system at a reduced price (possibly a loss for the upgrade) to the customer.
• Hand over the dispute to the lawyers. Be prepared to demonstrate that your existing design meets the specifications.

When I was on the construction side of the fence, I tried never to present a problem that would discredit the engineer or architect I was working with. Instead present them with a "better" solution to what they all ready (maybe) new.

They don't want contractors to fail and will generally work with you if you don't immediately put them on the defensive. We have stock forms that contain language I hope I never have to use.

The request involves a patent ambiguity or conflict in the documents that should have been addressed during bidding. Provide the better quality or greater quantity work, in accordance with Supplemental General Conditions.

It would have been a good idea to bring this up during the bidding phase. An addendum could then have been written to address the problem and keep the bidders on the same page.

A project manager would also of an engineering background for this.

This is a situation that does occur. One of the thing at time the customer may not have it in there budget at the time to spec. when caught it should be pointed out. There is to blame on both parties, But the customers should pay for the up grade, and the cost of restock charges if it can be returned be shared.

Unless it is the contract requirements from the customer, then it is the customs responsibility, and if they had a consultant, they should turn it over to them for compensation.

It comes down to not pointing fingers (but in essense it is), but accountability.

Dear Guest,

This matter I wanted to reply in the morning but there was some problem in the net.

1.ABOUT INSTALLATION:

The MOTOR H.P. is 150, Full Load current asper Name Plate is 190 Amps but actual is 209 Amps. Starter is SOFT STARTER but details are not furnished in your note. You have not mentioned the speed of the motor. If the speed is 2900 rpm, Power Factor will be bettter and for 750 rpm the power factor will be poor, for 600 rpm, the Power Factor will be still poorer.

Two alternators of 112 kW which means 149.33 H.P each.

2. MY OBSERVATION and RECOMMENDATIONS.:

1. Full Load current Level is alright. If the Power factor is 0.8, the full load current will be 203.66 Amps, but the name plate current is 190 A, and motor manufacturer might have have considered a Power Factor of 0.85 which is also correct.

2. You cannot start a 150 H.P Motor with one Generator of 112kW (150 H.P.), even with Soft Starter. To start this motor, YOU HAVE TO START BOTH GENERATORS and SYNCHRONISE IT and THEN START THE MOTOR.

It is NOT CLEAR from your text whether you have started 2 generators and synchronised to sart the motor. If not tried please try and you may succeed in starting the motor.

3.The selection and sizing of the equipment there is a confusion or bungling and as a man on the spot you have to handle the matter and you are responsible - which is understandable. This is a case of high order irresponsibility by your predecessors.

4. There are lot of discussions in this forum on the capacity needed for a generator to start a motor. Please search in this CR4 links and you will have lot of deails and you can DEFINITELY SOLVE YOUR PROBLEM.

5. MAINLY THE CONSULTANT and the PLANT IN-CHARGE , whether he is CIVIL, OR MECHANICAL, OR ELECTRICAL or ordinary Graduate IS RESPONSIBE, for all these activities in selection of the equipments and CANNOT SHIRK AWAY FROM THE RESPONSIBILITY. If Office Manager has simply stamped and APPROVED he should not be spared and taken to task.

6. I am very eager to know the out come of the issue and i request you to start both generators and synchronise and then start the motor. Please check-up the Droop Character of both Generators for Voltage and Droop Character of the Governor of te Diesel Engine of the Generator for Speed Character. This is very essential. If it does not match, then LOAD-SHARING by the GENERATORS WILL BE A PROBLEM which may be further head-ache.

Please inform the out-come of the issue.

DHAYANANDHAN.S,

CR4 MEMBER,

INDIA

This situation does occur in India quite frequently.Most consultants will qualify their approval with a statement that approval does not relieve the contractor or supplier from carrying out what is required to ensure proper completion and functioning.Now coming to the issue if 112 kw is only is in document.The standard motors should work at 415V+- 6% .When -6% is applied it becomes 390 approx.with this if u calculate the current it may well exceed the 212A.This should have been considered while designing the starter.Motor full load eff and Pf are also to be known.If it is not clear these parameters should have been asked or you should have qualified your offer with a protective clause.However in your drawings and data sheets if u have clearly mentioned the parameters and what current starter can handle and by approving it he has accepted it and you need not worry. by the way have u received the payment.?