120 to 480??

[Joethemechanic]

And yes, a center tap ground would normally be the safest. It will limit your phase to ground potential to 240V. Most electrical shocks/electrocutions are phase to ground

 

[jim dungar]

And yes, a center tap ground would normally be the safest. It will limit your phase to ground potential to 240V. Most electrical shocks/electrocutions are phase to ground

One of the most dangerous voltages we use is 277V L-G.

 

[Joethemechanic]

One of the most dangerous voltages we use is 277V L-G.

Yeah, it does not sound like much more than 240V but compared to a center grounded 240 volt secondary, it is well over double the voltage. L-G

 

[kwired]

Unless you had a 480V single phase motor. Not common, but no reason it can not be done.


In reality, there are no single phase motors. There are just motors with built in phase converters, and universal motors which are really DC machines.

Single phase induction motors are really two phase motors. The most common ones use a capacitor to shift the phase 90 degrees in order to produce the second phase. Some only use this second phase for starting, and some use it the whole time they are operating.


There are some exceptions to this, such as "shaded pole" motors, but these are mostly small very fractional horsepower devices used in small ventilation fans, clocks,,,,,,,,,,,,,

The shading coil in a shaded pole motor makes a phase shift just like other methods, it may not be as much of a shift , and certainly does not create a high level of torque, which is why these motors are not used where high torque is needed.

 

[Joethemechanic]

The shading coil in a shaded pole motor makes a phase shift just like other methods, it may not be as much of a shift , and certainly does not create a high level of torque, which is why these motors are not used where high torque is needed.

I'm a little low on shaded pole motor theory, I either never knew much about them, or maybe I forgot,,,,,, who knows,,,


But isn't there something to do with a shaded pole motor not overheating when it is stalled? Say something like would happen in a bearing seizure situation?

 

[Besoeker]

So will grounding the center tap on the 480 side be a safer install?

Will there be a centre tap on the 480V winding?
With the arrangement in post #4 there isn't one shown.

 

[kwired]

I'm a little low on shaded pole motor theory, I either never knew much about them, or maybe I forgot,,,,,, who knows,,,


But isn't there something to do with a shaded pole motor not overheating when it is stalled? Say something like would happen in a bearing seizure situation?

The small open frame type are typically "impedance protected" and usually marked so. They will still get hot when locked rotor occurs but not hot enough to destroy them like other motors. If left long enough they often will fail but we are talking a long time as compared to other types of motors. The larger ones probably could overheat in shorter time but usually have a thermal protector within the motor.