Transformer no output voltage

Gadelric

Member
Join Date
Nov 2018
Location
Midwest
Posts
137
Wizards,

Although this is not PLC related, I believe some of you wizards might be able to point us in a direction as I have limited experiences with troubleshooting transformers.

Back Story: Forklift driver hit the dock plate control box, the door got tweeked, one of the push buttons got smashed and nothing would work.


We pounded the door and box back into shape and replaced the PB.
Upon powering back up, we had no 120v out of the transformer.
Got a new transformer, no 120v output.
We have 280v coming in on leg 1 and 2, leg 3 doesn't go to the transformer.
We do not have any output voltage.
We tried 3 different transformers, same results.

We are fortunate that there is a second box that runs another dock that we closed off.
We have "robbed" the 120v output from that transformer to apply voltage to the dock that we need to use, which tells me the rest of the box works.

I am unable to do much during the day, as we cant have this dock down for longer than 20 min. All the work is getting done by.... 3rd shift maint staff....

Any advice I can give them, or at least some direction?

Gad
 
Do you have a picture of the transformer you can post? Some control transformers have integrated fuse blocks. Perhaps there is no fuse in the secondary circuit?
 
The voltage of 280 is leg to ground.
This is the tansformer that is used in the equipment.
This is the exact same transformer that was originally in this equipment.
It is wired the exact same way as the original one we pulled out.
It is also wired the exact same way as the transformer that we are "robbing" from.
https://midlandelectricsupply.com/product/b200btz13rbf/


There is a bridge that is installed between H3 and H2 for a 460 supply to generate the 120v output we desire.

The Primary windings ohm out as expected. H1-H2 is aprox 11 ohms with H3-H4 also having about 11 ohms, with the bridge installed H1-H4 is about 23 ohms.

The secondary winding ohms out with 1.2 ohms.


There are 4 terminals on the secondary winding side.

Terminal 1 - common

Terminal 4- +V

Terminal 2 and 3 are separate from 1 and 4, but are internally connected.
We fuse terminal 4 to terminal 2 and the fused leg goes to the PB on the panel front via terminal 3.
Terminal 4 goes to another fuse bank that provides 120v to the rest of the system.
Terminal 1 is common/ground


We thought maybe we had a dead leg, but the rest of the hi voltage side works the only thing we are robbing from the other cabinet is the 120v.
Although not desired, the maint staff are ready to just run a wip to a 120v outlet and bypass the transformer all together.


:unsure::unsure:
 
1)Do you have 480 on H1 to H4?
2)The picture shows fuses. All are good? looks like two fuses on the primary and one fuse on secondary
3) do you have 120 vac if you measure between terminal X4 and terminal X1 on secondary? all 120 vac should come from here
Looking at wiring diagram it looks like 120vac should be term 4 to term 1, you mentioned terminal 3? feeding pb on front? I don't think it is used for 120vac?
if you have 480 at H1 and H4 and nothing at x1 to X4 then either transformer windings are open or fuse(S) blown.
If you have 120 between x4 and x1 but not x3 and x1 then move wire from x3 to x4
hope that helps.
 



PDF, page 1, Primary identification label, shows a bridge between H2 and H3 for 460,440,&480.
Primary id label also shows a jumper between H1 and H3 as well as H2 and H4 for 220,230, & 240.

I am no expert on these by any means, but the bridge between H2 and H3 is how the original one was done as well as the working one in the other cabinet.
 
1)Do you have 480 on H1 to H4?
2)The picture shows fuses. All are good? looks like two fuses on the primary and one fuse on secondary
3) do you have 120 vac if you measure between terminal X4 and terminal X1 on secondary? all 120 vac should come from here
Looking at wiring diagram it looks like 120vac should be term 4 to term 1, you mentioned terminal 3? feeding pb on front? I don't think it is used for 120vac?
if you have 480 at H1 and H4 and nothing at x1 to X4 then either transformer windings are open or fuse(S) blown.
If you have 120 between x4 and x1 but not x3 and x1 then move wire from x3 to x4
hope that helps.




1.) We have 488.6 across the primary winding H1 and H4
2.) All fuses are good, and have been replaced just in case, they have also been removed from the working transformer and those ones used, and then replaced back into the working one.
Fuse on the secondary winding that fuses x4 to x2 has been tested as well as removed in an attempt to get 120 out of the secondary winding.
3.) There is no voltage across 1 and 4 on the secondary winding.
There are 2 push buttons on the front panel to activate the dock plate. Voltage is applied to these push buttons via Terminal 3 (fused leg) Terminals 2 and 3 are internally fused but not connected to the secondary winding. We fuse from 4 to 2 because of the needed space and 2 transfers power to 3.

4.) I will check all the fuses again at shift change.


I appreciate all the help you guys are providing.
Something this simple should not be causing them this much of a headache.

Gad
 
I am unable to provide an answer directly, the one I have here at my desk has and Open Line between x1 and x2, x1 and x3, and 1.2 ohms between x1 and x4. x2 and x3 are sub ohm.

I'm tasking the maint staff with pulling some ohm readings from the last one they installed. I wont be giving them what they should be looking for so they don't pencil whip it.
I will provide an update.
In the end, i might end up coming in at 3am to wire this thing up and pull some readings off of the secondary winding prior to landing the box to it.
 
Are you testing after hooking up the secondary wires? Can you test one with the 480 on just the primary and take reading on the secondary without any wires landed on the secondary?
 
here is what i suggest.

get a pig tail and have a 1 amp fuse in lime with the L1 side and wire up the transformer to see if you get 110 volts out. if so, the transformer is wired correctly.

if you get 110 volts, there is other issues in the damaged box.
blown primary fuse
blown secondary fuse
both are blown
component was damaged/destroyed in the damaged box
bad connection.
bad circuit board

hope this helps,
james
 

Similar Topics

Folks, I am designing a control system for an industrial machine. Machine is 480VAC / 3PH powered. And I have a 480 / 120V transformer for control...
Replies
9
Views
1,345
Hi all, I know this sounds like a dumb question, but.....I'm thinking out loud...and maybe I shouldn't do that.... Upcoming project involves...
Replies
16
Views
4,141
Ignore - I asked this question already and found my answer.
Replies
0
Views
1,023
Hi all Where can i find this transformer ? Pri 480 v 3x 0.12 A Sec 400 v 3x 0.12 A 3 phase Type DTS 80 50/60 Hz
Replies
14
Views
3,538
Greetings experts, Can current transformers be used on the incoming mains (480, 3P) of a machine that has regenerative VFD's? Current...
Replies
9
Views
3,179
Back
Top Bottom