DIGITAL ELCID TEST- ELECTROMAGNETIC CORE IMPERFECTION DETECTOR TEST

 

DIGITAL ELCID TEST-

ELECTROMAGNETIC CORE IMPERFECTION DETECTOR

Temp: 40°C

Test equipments:

1) Computerized Digital test kit (Adwel)

2) Voltage source Variac: 0 - 240 V, 30 A, 50 Hz

3) Clamp meter, Fluke make

4) Voltmeter, 0-230V, Fluke make

5) Lap top computer

Test details:

The required excitation voltage for the single turn trace winding at the test level of 4% rated core flux is given by

Where                        

Vt         =          Test voltage measured in trace winding

Vp-p    =          Rated phase to phase voltage

Tp        =          Turns in series per phase

K          =          Pitch Factor (0.92 for all generators)

Stator Core Details:

No of slots                                           -

48

Test Set Up:

No. of turns of the Excitation Winding –

12

From the above formula single turn

Measured excitation voltage per turn	8.58
Recommended excitation voltage per	8.63
Excitation Current	4.5Amp/turn

Analysis:

The pickup circulating current in all the slots was found to be less than 100 mA indicating the healthiness of the core.

 

NOTE: SLOT NO.1 MARKED AT 6 CLOCK POSSION AND MEASUREMENT DONE (SLOT NO. 1 TO 48) CLOCKWISE FROM THE EXCITER END.

 TYPICALLY

 HYDRO GENERATOR EXCITATION SYSTEM

 

 

 

SYSTEM CONFIGURATION

 

POSITIONING OF CHATTHOCK

 

STATOR ANALYSIS

 

 

 

INTERPRETATION OF DATA

MESUARING FAULT CURENT WITH CHATTOCK METER

 

 

 

 

Why Test Stator Cores?

 

Elevated "Eddy Currents" create hot spots which in effect can cause further and unpredictable deterioration to the core lamination insulation or to the actual core itself (core melting). Undetected and unchecked, this can lead to stator winding insulation damage, forcing the machine to be out of service.

 

EL CID is a cost effective maintenance tool for verifying stator core lamination integrity.

 

EL CID testing is able to:

Identify existing damage and localizing it

Reduce time of planned or forced outage

Advantages of EL CID Testing

Very small excitation power demand ~ 4%

Simple and easy setup

Elimination of further damage

Reduction in safety hazards

Reasons for Stator Iron Core Damage:

Compression plate relaxation

Loose bars and wedges

Foreign magnetic objects

Thermal core creeping

Interlaminar iron core insulation failure

Oil contamination

Incorrect wedging system installation