Motor supply problems

[hoolko]

i have dc motor 90v.....0.1Nm....0.4A.....i will be using 110 ac input....can i use a bridge rectifier or do i need an acdc transformer? will be using a speed control on motor..thanks, Nick

 

[john monks]

A bridge rectifier will work. You can use aa AC transformer before the bridge to lower the voltage to about 90 volts or a little less.

 

[hoolko]

A bridge rectifier will work. You can use aa AC transformer before the bridge to lower the voltage to about 90 volts or a little less.

thank you very much.....i find this very confusing...im happy to pay you for your knowledge if you can tell me what exactly i need and where i can purchase from a good site? Nick

 

[Electrobrains]

As John says, a transformer is a very good and professional solution.

If you just use the motor occasionally and don't care about efficiency, you could instead add a serial resistor in the 110V AC line before the rectifier.
For instance, roughly estimated, you could put two 12V/5W filament car bulbs in series with the rectifier.

(For better efficiency, instead of a serial resistor, you could use an AC capacitor, but that will also cost a bit)

Our suggestions are given for direct rectification of the AC voltage. I suppose the DC motor would run well that way.
If you would need a smoother DC voltage, you would need to add a capacitor at the DC side of the rectifier. But that would raise the output voltage and the transformer/resistor/capacitor would need to be adapted to the size of the capacitor.

EDIT:
If you have a "speed controller on motor", perhaps you should tell which type you are using. If it's some electro-mechanical type, it might be fine.
But if you have an electronic controller that is supplied from the 90VDC, it must be able to handle the peaks of the transformed or resistor-attenuated (rectified) sine wave. It also must be able to work from an un-smoothed DC voltage. Otherwise the solution with a smoothing capacitor is needed.