PW ENGINES CUT OFF

Phil,

This has come up on here from time to time.

It seems that some open frame postwar engines cause some voltage spiking that the TPC interprets as an overload and shuts down. Not all do it - it's unpredictable. 

The use of capacitors at the motor brushes has been suggested, but I haven't found a fool-proof cure.

Maybe this time someone will chime in with the definitive solution.

Jim

As Jim pointed out try using some capacitors. Also you can add shunted brushes along with the caps.

Bill

Phil,

I posted this a while back, but cannot seem to find it in the archives:

"The problem is the tender. More specifically the relay.

I ran into this after buying a postwar tender for my 1666. Even though it was in good condition I cleaned the motor and checked the wiring. When I checked it out on the track by itself it would work fine running the whistle motor, but would kick out the TPC when moved along the track with the AC voltage on.

The problem is that the DC relay for the whistle has inductance and is connected to the AC track voltage even when not being activated. (Remember that the whistle motor itself is not connected with the relay off.) Even with clean pick-up rollers there are inevitable minute breaks in the circuit which cause an "inductive kick" from the relay. This produces a voltage spike on the track power. While troubleshooting I saw this on my multi-meter and was able to reduce the voltage level (and the TPC drop-out) by using a non-polarized capacitor. Larger value was better. However, not having an oscilloscope, I am not comfortable with this approach alone. I plan on using a TVS in the tender instead.

Without adding the components mentioned, it may be possible to subdue this effect somewhat if the whistle w/relay is run in a train with active motors and incandescent lighting. These may absorb some of the energy before the level of the voltage spike can climb.

My postwar diesels' horn relays do not cause a problem, but of course, they are always directly combined with a motor and lamps."

Dave

so this happens whether you activate the whistle or not?? also i don't have any electrical knowledge so shunted brushes or capacitor...i can go to radio shack but will need drawing...thanks

Phil,

To verify that this is indeed your problem, remove everything from the track. Place only the tender, from one of the problem trains, on the track controlled by the TPC. Set the track voltage to about 12 volts. Give the tender a push by hand and see if it trips the TPC.

If it does, do a search for TVS (Transient Voltage Suppressor) on this forum and it will bring up threads about using them to protect the electronics in engines.

Your problem is similar except that it would clamp the voltage spikes at their source, the tender, and keep them from affecting other equipment.

I would place one in the tender between the center-rail power connection point at the relay, and a convenient frame-ground location (which goes to the outside rails via the wheels).

You can also place one across the output terminals of the TPC to help with protection all the time.

Dave

I'd also suggest the shunted brushes with the caps, one on each brush to frame.  Another thing that might help is a TVS across the rollers to the frame to zap any spikes before they leave the engine.

This is the TVS I'd use: 1.5KE36CA at Digikey

Lionel Modern engines have brushes that have braided copper leads.  The copper braid is attached to the electrical joint.  This is electrically quieter than the bouncing contact on the spring.  The cap is than added.  Use Non Polarized caps and that bridge the brush connection and CHassis ground.

Or you can shift to a different transformer or a simpler Power Master for a PW loop.  PM is less sensitive to PW motors and tender whistles.  G

Another way to check to see if the whistle relay is the problem and not the engines themselves would be to either use a non whistle tender or place a piece of tape over the tender's center rail rollers. 

J White