John is correct about the ML-3R center pin being intended for neutral in a 120/240 system. However you will find this connector used by Teletype and others for 120v with the center pin as chassis ground. So always double check when making up a power cord for a piece of gear. 

My favorite (not really) gotcha is some military 3-pin power cords with ground on pin C for early equipment and on pin B for later ones. Danger, Will Robinson!!

Cheers
Nick K4NYW 

On Sun, Jan 30, 2022 at 11:33 PM John W9DDD <w9ddd@tapr.org> wrote:
One nit I would pick is that for the 7484, the middle pin is not for ground, but for the neutral conductor.  Yes it might eventually get to ground, but it is considered a circuit conductor back to the breaker (or fuse) panel.  Note rating of 15A 125/250V AC, 3 Pole, 3 Wire  vs 125V 2 pole for the 7593.

In other words the 7484 is designed for use on a 230 volt appliance and the 7593 for 115 volt appliances. That being said doesn't mean people may have used the 7484 on a 115 volt device incorrectly.

Did I manage to make a mountain out of a molehill or what?

John, W9DDD


On Jan 30, 2022, at 5:38 PM, Nick England <navy.radio@gmail.com> wrote:

For future reference,
NEMA ML-3R 3-pin midget twist-lock female
1-11/64" diameter
NOTE - The ground pin is FEMALE
example - Hubbell 7484

NEMA ML-2R 3-pin midget twist-lock female
1-11/64" diameter
NOTE - The ground pin is MALE
example - Hubbell 7593

NEMA ML-1R 2-pin midget twist-lock female - 31/32" dia
NOTE - no ground pin
example - Hubbell  7464V

Having opened my big mouth, I am now sure I have mistyped something - double check to be sure..........

Cheers,
Nick England K4NYW
www.navy-radio.com
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