Grounding of secondary side transformer

[wv123456789]

TL;DR Summary

Grounding of secondary side of transformer

Hello,

I am a mech engineer teaching myself electrical engineering so please forgive my ignorance. Could someone explain to me how the coil stays open when grounded in the figure 2-12b.

With my limited understanding I can see that in 2-13a the if the side of the circuit on the left of the coil contacted ground (earth fault) then because of grounding at L2 both sides of the secondary windings would be at the same voltage so no current. In 2-13b grounding at L1 means that because of the Earth fault ground is now hot, current would pass through grounding at L1, bypassing the stop and into the coil? Is that correct?

many thanks,

will

 

[Baluncore]

Welcome to PF.
In (a), grounding any point between L1 and the motor, would blow the fuse.
In (b), grounding any point between L1 and the motor, could start the motor without blowing the fuse.

 

[Averagesupernova]

Figure 2-13A is not ideal either. Overload relay labeled OL should not be in the low side. A fault to ground between M and OL can exist for years without anyone realizing it until one day due to an overload condition on the motor causes the overload relay to trip and it has been bypassed due to an undetected fault between M and OL.