Converting a DC Loco Motor to AC Question . . . .

[Bob Baker]

Good Evening,

If anyone has a link to a video/diagram/ etc. that shows how to use a bridge rectifier to convert a DC motor to AC, I'd appreciate it.  I got an industrial switcher off of ebay that has a DC only motor and I need to convert it if possible.  Thank you for your time.

                                                                 -Bob Baker

[lionelsoni]

The bridge rectifier has 4 terminals, probably marked +, -, ~, and another ~.  Connect the + and - to the motor terminals.  Connect one of the ~ terminals to the locomotive frame or something that is connected to the wheels and thus to the outside rails.  Connect the other ~ to the pickup(s).

Keep in mind that the locomotive will always run in the same direction, unless you also install an e-unit (reversing unit).

[Bob Baker]

Mr. Nelson,

 

Thank you tremendously.  I will give this a shot and see how it goes.

 

                                                               -Bob Baker

[stebbycentral]

You have lost me here Bob.  My understanding is that a rectifier only works to convert AC to DC.  Not in the other direction.  To convert DC to AC what you need is a device called an "inverter",  The ones that I am familiar with are not simple solid state devices that would fit in a model train.  They are things the size of a toaster or larger.

In the end it may be easier just to swap out the DC motor for a universal motor.

[lionelsoni]

He's got a DC motor that he wants to run on AC.  To do that, he needs to convert the AC voltage to DC.

In any case, inverters are more complicated; but they can be very small.  It depends on how much power is involved and at what frequency.

[stebbycentral]

You are right, I misread the posting.  Which proves only that I shouldn't be responding to questions at 6:30AM.

 

[Dave632]

stebbycentral

You have lost me here Bob.  My understanding is that a rectifier only works to convert AC to DC.  Not in the other direction.  To convert DC to AC what you need is a device called an "inverter",  The ones that I am familiar with are not simple solid state devices that would fit in a model train.  They are things the size of a toaster or larger.

In the end it may be easier just to swap out the DC motor for a universal motor.

You are correct. The smallest power inverter I found was about 30 watts. There may be smaller ones out there.

[lionelsoni]

I think you're looking only at inverters that are meant for powering small appliances at the usual power-line voltage (120 volts in the US).  There would be little demand for these in sizes too small to power the smallest appliances.

But inverters are ubiquitous in compact fluorescent lamps and increasing replacing passive ballasts for conventional fluorescent lamps.  Many of these dedicated or embedded inverters run at frequencies much higher than 60 hertz, to reduce the size of any associated transformers or other magnetic components.  Inverters are also used as components in switching power supplies.  Computers are full of them, including extremely tiny ones mounted on circuit cards to power very small amounts of logic circuits. 

[gunrunnerjohn]

For $15 you can have the Lionel reverse unit that will allow you to run this in either direction using transformer control.

[phillyreading]

Another option which will be a little more expensive is to buy a reverse unit from Bachmann/Williams and use it. However the bridge rectifier is the easier and cheaper way to go, make sure it is rated for 6 amps 50 volts. Mouser Electronics has them and Radio Shack.