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4 Tests That Determine The Efficiency Of Power Transformers

4 Tests That Determine The Efficiency Of Power Transformers

Power transformers that increase and decrease electrical voltage are used in numerous public utility and industrial applications. They are necessary to enhance the safety and efficiency of power systems, and there are certain factors to consider for transformer selection. Because of their fundamental purpose, it is important to make sure that power transformers are always in their best condition.

Diligent testing prior to their installation and throughout their lifetime should be done to ensure the suitability of the power transformer for the system being used as well as for its continued efficiency. Without proper testing, a transformer may face several issues later on that would require a power transformer rewinding service or replacement.

Below are four types of tests that should be done on power transformers to guarantee their suitability and efficiency.

1. Turns Ratio Testing

The turns ratio test is commonly used to identify the winding ratio between the primary and secondary coils of a transformer and to make sure that they follow the recommended specifications. In other words, the turns ratio test confirms that the power transformer has the correct ratio of primary to secondary turns.

Apart from this, the turns ratio test is also conducted to make sure that the transformer will deliver the proper step-up or step-down voltage. For instance, a step-down power transformer made of 100 primary turns and 10 secondary turns will operate to decrease the voltage by a factor of 10 while multiplying the current by 10 at the same time.

2. Power Factor Testing

The power factor test is used to measure the power angle of the resulting current of power that occurs upon the application of AC voltage in order to identify the loss of power of the transformer’s insulation system. To achieve optimal results, the angle of the current must be 90 degrees. However, insulation is usually never perfect. Hence, a current measure close to 90 degrees is sufficient to attain better insulation

The power factor test is typically done with a power factor test kit. It can be completed regularly throughout the power transformer’s lifespan. This test essentially helps electricians or engineers detect a malfunctioning or deteriorating insulation over time and give them an idea when the transformer requires a replacement.

3. Insulation Resistance Testing

The insulation resistance test or Megger test is used to measure the quality of insulation within the power transformer. This test is usually performed with a megohmmeter, which is a transformer test instrument that operates similarly to a multi-meter but with a higher capacity. To pass the test, the transformer’s insulation should have a greater resistance than that prescribed by international standards for the transformer type.

The insulation resistance test involves determining a device’s insulation resistance while the neutral and phase are short-circuited together. When this test is conducted, the tank and core must always be grounded and every winding should be short-circuited at the bushing terminals. The resistance between each winding and ground are then measured.

4. Resistance Testing

The resistance test is done several hours after a power transformer has reached the same temperature as its environment and has stopped conducting current. This test is performed to identify differences in resistance between the windings and openings in the connections. It ensures the proper wiring of every circuit as well as the tightness of all the connections.

The resistance test is typically conducted with the use of a transformer ohmmeter. Winding resistance is calculated by measuring the current and voltage at the same time. Ideally, the measured current should be as close to the rated current as possible. By carrying out this test, electricians or engineers will be able to calculate and compensate for any losses of load as a whole.

There are actually many types of tests that can be performed on a power transformer to determine its condition and efficiency. However, the four tests mentioned in this article – turns ratio, power factor, insulation resistance, and resistance testing – are the most common and critical for maintaining the quality and integrity of the transformer. Without them, the operations of a power transformer can be seriously compromised.

When performing a transformer test, it is highly advised to seek the help of a specialist. There are several electrical and mechanical engineering companies in Singapore that provide reliable services for transformers and other types of equipment, such as power transformer installation, transformer testing, switchgear testing, electric motor rewinds, and more. Their expertise is essential in ensuring that any tests or services are performed effectively and safely.