How can phasing of two transformers in parallel be accomplished?

Phasing two transformers in parallel is crucial to ensure that they operate effectively and efficiently as a single unit. The correct method for determining the phase relationship between the two transformers is by using a multimeter. This instrument can measure voltage in the secondary circuit of both transformers when they are energized.

When using a multimeter, you can check the voltage output of each transformer. By measuring the phase voltage and ensuring that they are in phase (i.e., they reach their peak voltage at the same time), you can confirm that they are correctly phased. If the measurements show that the voltages are out of phase, adjustments can be made, such as swapping connections at the secondary winding, to achieve proper phasing.

Other devices, such as a clamp-on ammeter or transformer tester, while useful for specific tasks related to electrical measurements, do not provide direct information about the phase relationship between the two transformers. An oscilloscope could theoretically analyze waveforms and help visualize phase differences, but it is more complex and not typically employed for this specific purpose in HVAC applications when a simple phase check can be performed with a multimeter. Thus, using a multimeter is the most straightforward and effective approach for phasing transformers in parallel.