Mexico Voltage: 460V/60Hz to 127V Explained

[Alan Sheedy]

TL;DR Summary

Voltages in Mexico

Hello
We are building a machine for a company in Mexico. They have stated that the 3 phase voltage is 460v 60hz. No problem there as we can fit a main motor with this voltage/frequency. But we need to fit a small single phase circulation pump in the machine, so I asked about the single phase voltage and they said 127v. I'm a mechanical engineer with a fair understanding of electrics (I think) Can anyone explain this to me?
Regards Alan

 

[DaveE]

The 3∅ 460V and 1∅ 127V must be from different sources, or there's a step down transformer involved. 460V 3∅ can have 266V from phase to neutral, but no less. Theoretically you could have an unbalanced neutral with 127V from phase to neutral, but this would be too weird, and difficult, for anyone to actually do, I think.

So in the EE labs I worked in for high power stuff we basically had two systems 480/277V 3∅ and 208/120V 3∅. the difference was two separate giant transformers at the power entrance to the building where these voltages were generated.

So, I think you just need to take them at their word. They probably have either source available. If you want a single 460V power source to your equipment, then you'll need a step down transformer (autotransformer?) to make the lower voltage.

 

[Baluncore]

Mexican residential 1PH is 127 V to neutral.
Residential 3PH is therefore; 127 * Sqrt(3) = 220 V.
Your customer claims to have industrial 3PH of 460 V.

https://en.wikipedia.org/wiki/Mains_electricity_by_country
Lists Mexico as; 1PH Residential 127 V; and 3PH as 220 V or 380 V.

https://www.worldstandards.eu/electricity/three-phase-electric-power/
Lists Mexico 3PH as; 127/220 V; 120/240 V; 440 V; 240/480 V.

I would expect industrial 3PH to be specified as 440 V or 480 V, NOT 460 V.
I think you should check the 3PH specification your customer has provided.
Industrial 440 V is double the 220 V domestic 3PH.
I think it likely that the customer receives a nominal 440 V 3PH, that typically measures 5% high at 460 V

 

[artis]

I can only say I too have never seen a 460 volt 3 phase standard.
@Alan Sheedy make sure to double, triple check.

 

[Baluncore]

Mexican industrial power distribution is specified as 480Y277V. That is also the voltage rating of the contactors and circuit breakers used. 480Y277V has 480 V between phases, 277 V between each phase and neutral.

A voltage drop of about 5% is expected in distribution, so the 3PH voltage falls from 480 V to 460 V. That is why a class of NEMA motors for use with 480 V 3PH are commonly specified as 230/460 V.

The Mexican residential distribution voltage is unrelated to the industrial distribution. Residential power is distributed to the street as 3PH, 220 V, with neutral. A single 127 V phase to neutral is then provided with the neutral to each residence.

 

[Windadct]

460V is the low end of the tolerance for 480V, so many machines were spec'd to this value.

As for the 127V - there a are number of buck/boost autotransformers giving 5-10-15% type steps. Probably best to just price one into the project.