Author Question: Why is single-phase power used for most HVACR residential and light commercial systems? What will ... (Read 163 times)

lracut11 · **on:** Jul 26, 2018

Why is single-phase power used for most HVACR residential and light commercial systems?

What will be an ideal response?

Question 2

Why is three-phase power most often used by large HVACR equipment operators?

What will be an ideal response?

Question 3

What attraction and repulsion behavior do the north and south poles of a magnet exhibit?

What will be an ideal response?

efwsefaw · **Reply #1 on:** Jul 26, 2018

Answer to Question 1

Single-phase power is more readily available than three phase power. Because of the popularity of single-phase power, a larger variety of equipment types and sizes are available.

Single-phase equipment is more readily available because it is often kept in stock at supply houses.

Answer to Question 2

Individual line current for a three-phase load is approximately 58 of a similarly sized single-phase load. Since wire is sized by current draw, reducing the line current also reduces the wire size and voltage drop. There is less power loss to transformers in using it.
Three phase motors are smaller, less expensive, more reliable, and more efficient than single phase. They do not require special capacitors to increase their starting torque.
Some three phase motors have an ability to correct the phase shift caused by some other inductive loads. Large commercial consumers of electric power are often faced with a surcharge that is applied to their base electrical rate when their power consumption is out of phase. Three phase motors can reduce or eliminate this surcharge by correcting the phase angle.

Answer to Question 3

Like poles repel each other and opposite poles attract.