4
\$\begingroup\$

I've built this 220v DC motor controller. I use a 2x110v - 2x15v transformer to power up the stator.

enter image description here

The transformer is a Myrra 45064 with the primary windings connected as follows: pins 1 and 9 connected to the mains, pins 4 and 6 in short.

On the secondary windings, i've connected pin 12 and 19 to a rectifier, and 14 and 17 in short.

When I plug it in at 220v AC, the transformer heats up very fast and outputs ~12V out of the expected 30V. Didn't keep it powered more then 6 seconds.

I thought that this pin configuration should connect the 2 halves of the transformer in series and output 15+15V.

Am I connecting them wrong, or there could be another cause for the high current through the transformer?

P.S.: The schematic on github shows a 3 port primary winding, however, the board is built with the connections done as explained above.

\$\endgroup\$
  • \$\begingroup\$ Try open secondary first and see that you have ~30V, then connect a few hundred ohms to it and see if it behaves as it should. If yes, then check the bridge, the capacitor, the wires, more than that I cannot help, this is a "blind answer" for my part. \$\endgroup\$ – Vlad Sep 10 '12 at 13:43
  • \$\begingroup\$ Have you tried it with the load disconnected? It sounds like you're simply overloading the transformer. \$\endgroup\$ – Dave Tweed Sep 10 '12 at 13:44
  • \$\begingroup\$ I've totally isolated the transformer, ran 220 through the extreme pins in the primary, short the middle primary pins. I've also separated the 2 secondaries. Voltage/secondary ~6V instead of 15. The trafo is new. No idea what's going on. \$\endgroup\$ – Valer Sep 10 '12 at 14:52
2
\$\begingroup\$

The Farnell page has a little better description of the wiring needed:

Primary Pin Connections        |    Secondary Pin Connections           
Style   0V  115V    0V   115V  |    0V  Vsec    0V  Vsec
UI39    1   4       9    6     |    17  19      14  12

It looks like connecting per this table parallels the primary winding to set the turns ratio for 115V input.

Based on that idea, it looks to me like pins 1 and 6 should see the AC and pins 4 and 9 should be connected together, to maintain the correct phasing of the primary.

\$\endgroup\$
  • \$\begingroup\$ Thanks! That was indeed the issue. I totally missed that wiring info. Fixed now :) \$\endgroup\$ – Valer Sep 10 '12 at 19:20

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.