For the efficiencies of the transformer what power factor

Question

SCOPE

Frequently an engineer is given the assignment to develop test procedures for new equipment that has been received.  The engineer's job may be a test engineer's job in a test or maintenance facility or the assignment is for training.  The scope of the project is to design a test procedure for a voltage transformer knowing limited nameplate information about it.  This part of the course will satisfy the requirement for the design portion and term project of the course.

PROBLEM

You have been given a transformer with the following information:

• Nameplate KVA is 50KVA
• Voltage  levels are 7200/240/120VAC
  • (the 240 V secondary is center tapped to give 120VAC(line-to-neutral)
• Frequency is 60Hz

Develop a series of step by step tests to measure and or calculate transformer parameters that would be suitable for publishing in a certified test report.  To be specific, the following data should be measured or calculated:

• Resistance of the high voltage winding
• Resistance of the low voltage winding
• High voltage side current for no load and full load tests OR Low voltage side current for no load and full load tests
• No load losses at nominal voltage
• Full load losses at nominal current
• Percent excitation current
• Percent Z at room temperature
• Percent R at room temperature
• Percent X at room temperature
• Percent regulation at 100% power factor
• Percent regulation at 80% power factor
• Efficiency at loads of 50%, 100%
• Polarity indications for the high voltage and low voltage winding

To find one or more of these parameters you will have to provide:

• Bill of Material for each test with chosen instrument model numbers, equipment accuracy specifications, and data sheets
• Equipment wiring diagram (a pictorial) showing equipment interconnection FOR EACH TEST
• A step by step procedure stating what you are testing, why you are testing it, and what data you expect to record
• What engineering formulas are required to calculate requested data.

Question about the project:

For the efficiencies of the transformer, what power factor are we assuming for the load? Also No load losses are the same as the losses in the Core resistance under open circuit test, correct?  Also do we have to do test for both the 120 tap and 240 tap?

Answer 1

Consider that you have been provided a transformer by the given details: • Nameplate KVA is 50KVA • Voltage levels are 7200/240/120VAC • Frequency is 60Hz Create a series of step by step tests to measure and or compute transformer parameters which would be appropriate for publishing in a certified test report. To be particular, the given data must be evaluated: i) Resistance of low voltage winding ii) Resistance of high voltage winding iii) High voltage side current for zero load and full load tests OR Low voltage side current for zero load and full load tests iv) No load losses at the nominal voltage v) Full load losses at nominal current In regards of efficiencies of the transformer, describe what power factor are we supposing for the load? As well No load losses are similar as losses in the Core resistance in open circuit test, correct? As well do we comprise to perform test for both the 120 tap and 240 tap?