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# 110AC to 140DC?

I've got a 140VDC motor from an old garage door opener. I want to use the motor for another purpose. The original controller board is fried. Will a bridge rectifier that can handle 110AC over power the motor?

160Views8Replies

I've got a 140VDC motor from an old garage door opener. I want to use the motor for another purpose. The original controller board is fried. Will a bridge rectifier that can handle 110AC over power the motor?

## Comments

Best Answer 5 years ago

I did this for a living years ago.

110 AC is about 170 DC when directly converting AC to DC, so it may work with just a rectifier as long as the rectifier is rated for the amperage.

Since it is 140 VDC and it will be getting 170 VDC it would be best to check it on a variable power supply and see if the current goes down as you approach 170 VDC, if the current goes down you are good to go.

If the current goes up as you approach 170 VDC you may need to step down the 110 VAC to about 90 VAC before converting to DC.

5 years ago

When you rectify 110VAC, it should end up being sqrt(2) times as much. (that is 110V times sqrt(2) is 155, and a full wave bridge rectifier might have some diode losses, take another couple volts off.)

Answer 5 years ago

It seems like you will end up pretty close to where you need to be in terms of voltage.

5 years ago

The opener was rated at 1HP, but I don't know if that was after gearing or before. I ordered a 1KV 50A rectifier, so there shouldn't be a problem with it handling it.

5 years ago

Be careful, your motor power (fractional horsepower or 3 HP or more ) may use more current then your bridge can handle.

Also US limits AC outlets to 20 amps which means a max of 3HP is allowed before the circuit breakers disconnect the power.

The bridge rectifier should be over 20 amps and over 170 volts DC output...

Answer 5 years ago

Is a Garage door opener ever likely to be 3HP ?

Answer 5 years ago

That would be 16 amps and the start up surge would be much higher.

Most of the ones I have seen are 1/3 horse geared down for power and speed.

5 years ago

It should be OK, with appropriate fusing.