TRANSFORMER SAFETY TEST

By Tom Jarcho

AN AMERICAN FLYER® REPAIR CLINIC

From Port Lines Hobbies

Old transformers should be very carefully tested and checked out before being installed in a layout, and should constantly be watched for signs of trouble. Here is some information on how to maximize safety when using them. NO TRANSFORMER IS TOTALLY SAFE, but following these suggestions will much reduce the chance of a mishap.

A transformer does not let only a little house current pass through to your trains. It uses the house current in its primary winding to generate a totally separate smaller current in its secondary winding. Thus the transformer has two jobs: to isolate your railroad from the house current and to provide electricity to it.

For your safety, there must be no continuity (electrical leakage) between primary and secondary, that is, between the house current and your railroad. There should also be no leakage between the power cord or the primary and any metal external parts (cases, rivets, bottoms, etc.) House current is much stronger than the current on which your trains run; it offers much greater shock hazard and can start a fire much more easily.

To test for this leakage, unplug transformer. Connect one end of a continuity tester to both prongs of the plug. Touch other end to all terminal posts with transformer at various speed settings. Any continuity indicates the transformer is no good and SHOULD NOT BE USED ! (except as a boat anchor)

Also test for leaks to the bottom plate and all metal external parts. While the transformer is unplugged, connect one end of continuity tester to both prongs of the plug at once. Touch the other end to all metal external transformer parts. If you locate any continuity, find & fix the leakage, or don't use the transformer. To be certain of test results, if the transformer has an on/off switch, run these continuity tests with the switch in both positions.

If your trains should start running faster than normal or lights burn more brightly, there may be a leak from the primary to the secondary. Very dangerous -- remove transformer and check it thoroughly.

A transformer should be producing close to its rated output of volts. You can measure the output with the AC Volts function of a VOM (Volt-Ohm meter).

Many, but not all, American Flyer transformers are equipped with circuit breakers, These are supposed to interrupt the flow from the transformer when there is a short circuit that could damage it. If the transformer label states that the unit is equipped with circuit breakers, thecircuit breakers can be tested. Here's how: with the transformer on, touch the ends of a wire to the fixed voltage post and the base post for 3 to 5 seconds, no more. Also test by holding the wire against the base post and the variable voltage post with the transformer set at half speed for 3 to 5 seconds, no more Here's what should happen: sparks should occur at first. If the circuit breaker kicks in, you should hear a click and sparking should stop. If you don't hear a click and the sparking doesn't stop, the circuit breaker does not work. NEVER HOLD THE WIRES AGAINST THE TERMINALS FOR MORE THAN 5 SECONDS MAXIMUM, AND DO NOT REPEAT THIS TEST TOO OFTEN. It is easy to damage a transformer this way. Some early Flyer transformers have adjustable circuit breakers with reset buttons. These may not make a clicking noise when they cut in. After the circuit breaker has thrown, the reset button must be pushed to reestablish the connection. See original Flyer instructions for info on adjusting these, if necessary.

A transformer should be thoroughly checked before being added to your layout. In addition to passing the tests described above,

 

SOME OTHER TRANSFORMER SAFETY SUGGESTIONS:

-Transformers with working circuit breakers are preferred, especially for running trains. Those without circuit breakers can be used to power accessories and lamps, but watch them closely for signs of trouble. Circuit breakers are good, but should not be relied upon. They will kick in and interrupt the current in case of a large short circuit but usually will not in case of a small one. Small short circuits can cause transformer damage too.

-Don't overload transformers. The more trains, lamps, and accessories you have, the more transformers you need. Original instruction books contain formulas for this, or you can ask your train dealer or a more experienced friend if you have any doubts.

-Transformers should be plugged into power strips, each containing a circuit breaker and an on/off switch so all power to the layout can be cut off quickly at the first sign of trouble.

For added safety you can equip the sockets you plug the power strips into with GFCI (ground fault circuit interrupter) sockets. GFCI sockets protect against line-to-ground shock hazards. They are especially recommended for basements where dampness or flooding can be a problem. Consult your electrician, who can install them for you.

-You should NEVER leave transformers on when you leave the room.

-You should have a smoke detector and a fire extinguisher in the train room. Check with your local fire department to see what extinguisher they recommend.

-Transformers should not be used where dampness and water are present.

-Transformers should be tested and inspected regularly. No compromises with safety should be accepted. Rollers should be inspected for wear and cracking.

-Wire your railroad carefully. Use good wiring techniques to keep trouble to a minimum. In addition, always listen for strange sounds on the layout. Short circuits and overheated solenoids can cause transformer damage. A burning out switch coil, for example, which makes a buzz, or any intermittent or partial short circuit could damage a transformer. Most toy train components will give off a smell if they overheat. Look out for these smells and sounds and act on the information they contain.

-Whenever you have any doubts about a transformer, disconnect and remove it from your layout and test and check it thoroughly. If you can't do this work yourself, have a more experienced/skilled friend or a repairman do it.

Finally, there is a small problem with the smaller American Flyer turret transformers, such as the 15B and 16B. On each end of the roller's path there is a plate. On these transformers there is a voltage difference of about 3 volts between the low end plate and the first winding. If the roller is left in a position near the lowest possible speed with the handle down, a dangerous overheating can occur in a s little as 10 seconds, eventually burning out the first few windings of the secondary coil. So don't leave the handle at almost slowest speed for any length of time. This problem does not occur in the larger turret transformers, 18B and up. You might want to remove the back plate and check this action out for yourself.

All this info is contained in my Roundhouse columns in S Gaugian magazine's May-June '98, July-August '98, and Sept-Oct '98 issues.

Tom Jarcho

 

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