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Transform your transformers

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The picture here shows that a transformer can also fail. That will happen especially with old transformers that suffered under the fatigue of heating and cooling cycles.

The lifetime of a transformer is between 25 and 40 years. How old is your transformer? 

Talking about your transformer means that we focus on stepdown transformers that are purchased by enterprises, which get their energy from the medium voltage power grid. As these transformers are installed after the main meter, you pay its losses. When the transformer is more than 20 years old, it is very probable that today’s transformers are much more efficient and will remain cooler. 

This week, an expert of large distribution transformers in the United States told me that the net present value of the losses in the lifetime of such transformers are mostly between 50 and 100% of the purchase price. In other words, the typical lifetime losses are a bit lower than the transformer itself.

How can you save energy with a new transformer? 
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  1. Buy a good one. Today's transformers are much better than when your current (old) transformer was purchased. The USA energy agency EPA tells that significant total life time cost savings are obtained if the new transformer is chosen BETTER than the law requires. Remember that you can deduct them for a long time from the taxable profit.

  2. Buy the right one. This is not about quality but size. Your today’s transformer is maybe dimensioned for a much higher power than is consumed most of the time. That choice is made to have a transformer that is able to work under all circumstances. You can purchase a new smaller transformer, based on the average power instead of the maximum possible power. This will decrease the losses because the transformer will function for many % of the operation hours in the best possible efficiency area. This is visible in the in the figure to the left where you see the efficiency of the transformer as function of its load. 
    You can always use the old transformer when there is a peak demand, automatically switching it on and off. Of course you will need the space for two transformers but the new transformer will be smaller. By the way, that will make it also cheaper than a full size replacement. 

  3. The transformer will be less efficient when the power factor of all the consumers in the enterprise is low. The power factor tells how well the current and voltage are in phase with each other. In the diagram the power factor is assumed to be 1.
    You can correct (increase) a low power factor with electronics and it will decrease not only the losses in your transformer but also the reactive power that you are using (and paying!). So you are saving in two ways.

2. Financial metrics

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3. When you are in a hurry, better keep it simple!

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In the previous newsletter of 22 March you read about the webinar for the Indian government. One of the Best Available Technologies (BAT) explained there was about the retrofit of ventilation systems: from belt driven to directly driven fans. In the PDF file next to this text you will find the slides that are explained here.

4. Practical and Compact course on Energy Management with inspiration

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