DIY Home Improvement Forum banner

1 - 3 of 3 Posts

·
Registered
Joined
·
1 Posts
Discussion Starter #1
There are breakers are on a secondary side of a 240/120 step down (winding type unverified but assumed to be an autotransformer).
Terminals on transformer are 2 in and 2 out, no ground terminal. Ground wire from 240V side is joined to ground wire going into 120 V breaker box. Neutral is not connected to ground in 120V breaker box. Outputs from transformer goes to live and neutral bars of 120V breaker respectively (no clear color coding on terminals)
While replace a outlet with breaker OFF the circuit was observed to still be live...
With no multimeter immediately available a blender was used to check the potential of the live wire.
Blender was connected between brown wire (the output of transformer in breaker path) and ground-[the brown wire was the presumed to the live wire].
Blender was observed to be on with breaker in both ON and OFF positions -spinning louder when breaker was off.
There is nothing else on the branch circuit besides the outlet. There were 2 other outlets on separate branch circuits from this box and their breakers were left ON. All 240 circuits were also ON during this test.
Later when a multimeter was available the following was measured with the circuit breaker ON:
L-N: 100V, L-GND 100 V, N-GND 200V
So far a friend EE suggests swapping L and N on the input of transformer to make the output neutral equipotential with the input neutral. However its still puzzling to me why the blender [connected to ground and the transformer secondary terminal in the breaker path] was running with the breaker OFF...
Can anyone explain what is happening there?
(This was done in a rural developing country so please take that into consideration-thanks!)
 

·
Naildriver
Joined
·
12,112 Posts
Your profile is not complete. Where are you located? This is primarily a North American forum, so information may be slow in coming.
 

·
Registered
Joined
·
3,257 Posts
You should have the breaker on the primary side of a buck boost transformer if you want to prevent feed through. There is a direct connection from the primary side to the secondary. Isolation is impossible regardless of how you connect the primary. That's a disadvantage you the buck/boost (autotransformer) transformer as opposed to an isolation transformer.
*
*
 

Attachments

1 - 3 of 3 Posts
Top