Monday, June 25, 2012

Types Of Electric Motor Testing

Repairing and maintaining large motors like turbine & hydro generators, large AC DC motors, diesel generators, transformers and many other kinds of heavy duty motors needs precise and accurate testing. Newton Electrical Equipment Inc specializes in this kind of equipments and would share some helpful information to keep the electric machines functions very efficient and in perfect condition to produce optimum results.

40kV Surge Testing

This test uses extremely short high voltage pulses to test electric windings and their insulation. This surge creates a voltage difference between turns. The turn to turn insulation is tested for quality. Turn to turn insulation weakness, incipient faults and all windings problems and faults are immediately visible on the oscilloscope screen.

Why Perform Surge Testing?

Insulation deterioration is one of the first signs that a motor is going to fail electrically. Since secondary insulation is least able to sustain wear, shorting usually occurs here before the thicker, ground wall insulation is affected. Surge testing is a non-destructive test and detects the early stages of secondary insulation deterioration.
The cost of motor failure is measured by interruption of plant output as well as extent of repair or replacement. Surge testing greatly decreases both. It detects failure early enough so that repair or replacement can be scheduled during a normal shutdown rather than an emergency outage. In addition, damage to the motor is minimized.

Power Factor & Dissipation Test

This is an AC test used to measure the bulk quality of the ground-wall insulation by measuring the dielectric loss per unit of volume of the insulation.

Tan delta testing - also called power factor testing (power factor is the same as tan delta within the low power factor ranges of practical electrical equipment). As power is defined as the rate of energy transfer, 'power dissipation' is a measure of the rate at which energy is dissipated, or lost, from an electrical system. When an electric current does work on a conductor, the internal energy of that conductor increases, causing its temperature to rise above the ambient (surrounding) temperature. This causes energy to dissipate away from the conductor into the surroundings, through the process of heat transfer. The rate of this heat transfer (joules per second) is termed 'power dissipation' (in watts).

EL-CID (Electro Magnetic Core Inspection Detection Test)

A portable test equipment for inspection of rotating electric machine stator cores.
Also known as Electromagnetic Core Imperfection Detector or EL CID, it was designed and used to detect insulation failures between laminations of stator cores in generators. We have been using this equipment to test large Generator and High Voltage motors of all sizes.
Originally developed by the CEGB in England, the EL CID Evolution is a third generation instrument that is proven, reliable and easy to use. The EL CID Evolution tests the condition of a stator core in less time and with fewer resources than the earlier EL CID models. The ELCID instrument can be used to test turbo-generators, hydro-generators, and large motors.
It has the advantage that it does not require a large energy source to test the largest machines, it requires only 4% of a machines rated flux using a toroidal winding of a few turns. A 3kva supply at 110volt is sufficient to excite a machine of several hundred MVA.

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