Shackled Designer
Member
- Location
- Decatur, AL USA
I see that there has been a previous post similar to what I am about to ask. However, in that case, one or two of the responders asked why the question mattered, and the OP apparently never offered an answer.
So, I have a buck transformer bumping 277VAC (single-phase) down to 230VAC. I am interested in calculating what the power dissipation would be at full load. My assumption is that power dissipation would be greatest at full load, but if this is wrong, please feel free to better inform me. So far, I have not found a manufacturer that publishes either full load transformer power dissipation or a dissipation curve vs. load %.
Before continuing with the numerical data, why is this important? Well in this case, the transformer is being installed in an enclosure with a number of other devices which also dissipate heat, and so I am attempting to calculate watt dissipation and thereby how much enclosure cooling I need.
Now, according to the transformer labeling, this is a 1.5 kVA transformer. However, in its buck configuration, it is acting as an 8.6 kVA transformer. According to the manufacturer's literature, in this arrangement and at full load, the transformer will convert 276VAC to 230VAC with respective primary and secondary currents of 31.3 and 37.5 amps. Calculating the power on both sides of the transformer, I have . . .
Primary: 276V * 31.3A = 8,638.8 VA
Secondary: 230V * 37.5A = 8,625 VA
Using only significant digits,
Primary: 8,640 VA
Secondary: 8,630 VA
The difference, then is 10 VA, and if the numbers are accurate, then I suppose this is my power loss. However, I am surprised that the number is this low. In fact, the difference might be a result of nothing more than decimal rounding. Is a mere 10 VA realistic for this case? Seems a bit low to me.
I reckon that the most reliable way to determine power loss is to measure primary/secondary voltage/current in the final system. However, that does not really help with a project in the planning stages.
So if the value I have calculated is not reality, what is a better way to estimate watt dissipation for this case?
Many thanks,
The Shackled Designer
So, I have a buck transformer bumping 277VAC (single-phase) down to 230VAC. I am interested in calculating what the power dissipation would be at full load. My assumption is that power dissipation would be greatest at full load, but if this is wrong, please feel free to better inform me. So far, I have not found a manufacturer that publishes either full load transformer power dissipation or a dissipation curve vs. load %.
Before continuing with the numerical data, why is this important? Well in this case, the transformer is being installed in an enclosure with a number of other devices which also dissipate heat, and so I am attempting to calculate watt dissipation and thereby how much enclosure cooling I need.
Now, according to the transformer labeling, this is a 1.5 kVA transformer. However, in its buck configuration, it is acting as an 8.6 kVA transformer. According to the manufacturer's literature, in this arrangement and at full load, the transformer will convert 276VAC to 230VAC with respective primary and secondary currents of 31.3 and 37.5 amps. Calculating the power on both sides of the transformer, I have . . .
Primary: 276V * 31.3A = 8,638.8 VA
Secondary: 230V * 37.5A = 8,625 VA
Using only significant digits,
Primary: 8,640 VA
Secondary: 8,630 VA
The difference, then is 10 VA, and if the numbers are accurate, then I suppose this is my power loss. However, I am surprised that the number is this low. In fact, the difference might be a result of nothing more than decimal rounding. Is a mere 10 VA realistic for this case? Seems a bit low to me.
I reckon that the most reliable way to determine power loss is to measure primary/secondary voltage/current in the final system. However, that does not really help with a project in the planning stages.
So if the value I have calculated is not reality, what is a better way to estimate watt dissipation for this case?
Many thanks,
The Shackled Designer