Burning pool motor connection

[kwired]

No, use square root of three.

Then there is efficiency, so input KW is greater than output KW always! Or you invented a perpetual motion machine....

I was going to chime in with the efficiency thing. No motor is 100% efficient, 746 kw per horsepower is the output rating, and that is assuming you are driving rated output load as well. Regardless input power will always be higher than output power. Then power factor will still result in higher VA than actual watts.

 

[FionaZuppa]

240v 3ph delta, 20A 7.5hp motor
that would appear to be running right at FLC

why does it run at FLC?

that said, the Burndy should not burn up. seems like a contact issue.

 

[ptonsparky]

240v 3ph delta, 20A 7.5hp motor
that would appear to be running right at FLC

why does it run at FLC?

that said, the Burndy should not burn up. seems like a contact issue.

Motors running at FLC means the motor has been properly matched to the load. I always like to think it was planning by someone and not by accident.

Too tight, too loose. Both result in burnt connections

 

[kwired]

240v 3ph delta, 20A 7.5hp motor
that would appear to be running right at FLC

why does it run at FLC?

that said, the Burndy should not burn up. seems like a contact issue.

Because the need was close to 7.5 HP, 10 HP motor cost more, and they likely intentionally designed this to get nearly everything they can out of the 7.5.

Seems most the irrigation pumps I wire up, you take an amp reading and they are drawing nearly FLC. I doubt it is coincidence, they knew approximately what HP was needed and if slightly over a standard size, tweaked a few things to get it down to that size, or if they needed 90 HP may tweak things to get closer to 100 hp. Tweaking things in this application is often using different specification on the sprinkler package to change overall flow rate.

 

[LarryFine]

IF the supply is 240 wye you need to specify that clearly, as it is relatively uncommon.

Well, here. That's the configuration of British, Australian, and other "250v" 1ph systems.

 

[kwired]

??
240 3ph wye (3P4W), where does 139v come from? Ph-N is 240v
sorry, i meant Y. but even with "3P4W 240v Open Delta" or the "3P3W 240 Delta", the ph-ph is 240v, and wild leg to N (B-N) is 208 while AC to N (A-N and C-N) is 120v.

What does your drawing of 415/240 wye have to do with this discussion?

If you have 240 volts three phase supply (doesn't matter if it comes from wye or delta source) and connect it to a wye wound motor, the voltage to the wye point in the motor will be 139 to each input lead (presuming you don't connect the wye point to anything else).