How to service a magnetic contactor?

27/07/2011 by 2 Comments

Magnetic contactor is a familiar device for control electrical motor,pump,capacitor and others.When it operate for long time,the main contact must be checked and cleaned due to sparking current during energized and de-energized.

We also must cleaning the dust or foreign material to avoid magnetic contactor mechanism stuck or cannot function properly.Normally i perform the services and cleaning jobs every 6 months.It depend on operating condition and last services.

During this services,we can checked the condition of contact point either is ok or not good.If the contact already worn or not in good shape,it need to replaced with a new one.It important to ensure the performance and operation is smooth and stable and current can flow through the contact without any problem. read more

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Vacuum circuit breaker

16/07/2011 by 2 Comments

As we know vacuum mean the the pressure is maintained below atmospheric pressure( unit : mm Hg ).So the manufacture made a research and development to design the vacuum circuit breaker based on current cannot jump in vacuum condition.

Vacuum Circuit Breaker used the vacuum pressured to extinguish the current arc when it switching.Normally this type of circuit breaker used for medium voltage ( 1 – 35 kV ) power supply.The ampere rating for vacuum circuit breaker is until 3000 ampere.

Vacuum Circuit Breaker have a  high insulating strength and capable to extinguish the current arc for medium voltage power supply.It more safe for switching and environment friendly.It only a vacuum atmosphere. read more

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Routine maintenace tests for circuit breaker

03/07/2011 by 3 Comments

Circuit breaker is the important protection device for our application and electrical power supply system.It can save our equipment or machinery from damage from over current or overload matter.It also can save personal life who involve directly or indirectly with electrical application from electric shock.

How we can know the actual condition and reliability for our circuit breaker? Normally we must perform the routine maintenance tests to determine out circuit breakers are able to perform their basic circuit protective functions and in good condition.

This time i want share information about routine maintenance tests for circuit breaker.Below i listed 5 types of tests to determine and assuring that the circuit breakers are functionally.Please be caution before perform the tests are to be made only on breakers and equipment that are on de-energized mode ( power supply OFF ). read more

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NEC calculation for overload sizing

01/07/2011 by 12 Comments

Sizing for overload is important to avoid serious damage for electrical application such as motor starter,machinery or others electrical equipment.

According to NEC,the general requirement for overload sizing be set around 115% or 125% from full load ampere.We should setting the overload relay within this parameter to avoid electric motor from serious damage.

For calculation of overload sizing,it depend on the motor full load ampere current rating,the service factor and temperature for motor.I already explain in my last post about several factor effected for overload relay sizing. read more

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Transformer rating

20/06/2011 by 2 Comments

Transformer rating or capacity depend on the  limited of insulation temperature can stand for maximum load.The ratings can be up or down when we reducing a  core and copper losses.

To reduce core and cooper losses,we can improved the rate of heat exchange with proper cooling system or by improving quality transformer insulation that can stand for high temperature.

For larger transformer types,we can remove more heat with increased area for efficient cooling and increased volume of oil to absorb more heat to reduce the temperature. read more

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Dual voltage motor

17/06/2011 by 18 Comments

If we take a look at electric motor nameplate,we can see the several important information and specification about electric motor.This time i want explain about dual voltage for power supply.

It is like a simple thing and not so important BUT if we make a mistake about electric motor voltage power supply,it can cause the winding damage and burn out.That why i would like to share about this information to avoid serious damage for electric motor.

The reason why motor manufacture design dual voltage is to make this motor available for any country used because every country have a different voltage value such as 200 VAC,600 VAC and 415 VAC.It also so for marketing strategy to increase their profit margin. read more

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Motor cooling

13/06/2011 by 4 Comments

Electric motor generated the heat from inductance process.So the temperature is important factor to ensure the electric motor can operated smoothly without any problem.

Heat can effected the efficiency of motor,maximum load capacity,duty cycle and winding lifespan.That why heat from motor operation must be controlled by motor cooling.

How to control temperature for electric motor?The best method is with motor cooling system.Basically heat generated during motor running will be transferred to the ambient air surrounding. read more

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