The DOE (Department of Energy)indicated was DOE/CE-0384 and is a document that had, among other info, average efficiencies for "standard" motors and "energy efficient" motors, also the average acquisition price for normal and more efficient motors. They considered between 7 - 20 manufacturers...
I agree that the manufacturer's catalogs are the best when dealing with a small number of motors, you look them up and use those numbers. The question was to find a "typical/default" value based on the latest requirements/standards (NEMA or similar) to be used in calculations.
In my...
The question, as mentioned in my first post, was what load to use in a power flow calculation and to determine the impact on the total energy comsumption by using more efficient motors.
Values based on National Electric Code (in the US), or similar codes in other countries, are not meant to...
rhatcher
Real power losses are also losses in windings. A higher power factor lowers the input current, so lower losses in feeders. But at the same time the reactive current (that provides magnetization) is also taken into account, so in the end it influences the motor efficiency.
Skogsgurra...
We were involved in an analysis of replacing "normal" efficiency motors by "high" efficiency motors. During the process one issue appeared. Below is a typical example.
One of the motors in question had following data:
(per NEC 2005 - Table 430.250 - typical motors)
Output power: 20 HP ( 14.92...
Sibeen, this was exactly the path we tried to reason. We proceeded by eliminating parts that had to be sized based on the kVA rating (input & output cables, rectifier, etc). We eliminated the battery, since that part is an emergency source that kicks in (normally) only when losing the power...
I agree that what finally matters are currents and voltages. But I think that in the operation of each device, whatever the brand, manufacturer, etc and the registered or non-registered trademarks used, in the end, everything can be traced back to basic laws of electrical engineering (applied...
If you have the 3 phases A,B,C and you can measure the real power with 2 Wattmeters, measuring the currents on only 2 phases, as follows:
Install W-meter 1 with currents terminals to measure IA (current in phase A) and with voltage terminals to measure voltage UAB (line-line voltage between...
Sibeen, if the (synchronous) generator is connected to a power grid with imposed frequency and voltage, the generator will generate power at those forced values. If you change the excitation to a value over of under the one required for a "real/ohmic" load (pf=1) at these values, it will...
Waross, what I meant is that between 2 points A (source) and B (load), the direction of the reactive power flow can be either from A to B or from B to A. The direction (from A to B) is generally considered to be positive (+) while from B to A it is considered as negative. Positive is referenced...
Waross, I agree with your explanation and the fact that a short circuited transformer represents an inductive load. We were looking to find an answer where the UPS provides the reactive power. The load (with an inductive power factor of 0.8) had to get that reactive power somewhere (from a...
Sibeen, when you say "from 0.8 lagging to 0.8 leading" do you mean (- for lagging and + for leading) (as an example)-0.8 , -0.9, 1, +0.9, +0.8 ? all at maximum apparent output power (kVA)? What is the reason for a 80 kW limit in this case ?
Waross, I am assuming that by the proposed solution in your response, if I understood correctly, to feed a Variac (autotransformer ?) from the UPS terminals and with its output connected to the primary of a normal transformer with short-circuited secondary, a reactive load could be simulated...
