# Question bridge H in controller Curtis 1244



## marcelo2112 (Mar 29, 2016)

Hello everyone, I am repairing a curtis 1244, I see that it has an H bridge to feed the motor rotor.
If the positive of the battery goes directly to the motor, why does it require a bridge h? Greetings and thanks.


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## jbman (Oct 26, 2017)

marcelo2112 said:


> Hello everyone, I am repairing a curtis 1244, I see that it has an H bridge to feed the motor rotor.
> 
> If the positive of the battery goes directly to the motor, why does it require a bridge h? Greetings and thanks.


To reverse the field coils for changing motor direction, I'd say.

Sent from my SM-N960U using Tapatalk


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## major (Apr 4, 2008)

marcelo2112 said:


> Hello everyone, I am repairing a curtis 1244, I see that it has an H bridge to feed the motor rotor.
> If the positive of the battery goes directly to the motor, why does it require a bridge h? Greetings and thanks.


The Curtis 1244 SepEx uses a full (H) bridge for the field (stator) and a half bridge for the armature (rotor).

major


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## marcelo2112 (Mar 29, 2016)

major said:


> The Curtis 1244 SepEx uses a full (H) bridge for the field (stator) and a half bridge for the armature (rotor).
> 
> major



Perfect, but why half a bridge in the rotor? To brake? I am changing mosfet and wanted to save me some of the half bridge high side, will it work? Thank you.


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## Russco (Dec 23, 2008)

marcelo2112 said:


> Perfect, but why half a bridge in the rotor? To brake? I am changing mosfet and wanted to save me some of the half bridge high side, will it work? Thank you.


Here's the Curtis Manual for the 1244:


http://www.fsip.biz/Documents/ACFWC9e9x.pdf


And it's an *Armature*, not a rotor. DC shunt wound motor.


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## major (Apr 4, 2008)

marcelo2112 said:


> Perfect, but why half a bridge in the rotor? To brake? I am changing mosfet and wanted to save me some of the half bridge high side, will it work? Thank you.


You need at least two switches. What I call a quarter bridge consist of a gated switch like a mosfet for the chopper and a diode for freewheeling giving single quadrant operation. A half bridge uses two gated switches (mosfets) with synchronous rectification and gets regenerative capability for two quadrant operation. The full H bridge is needed for 4 quadrant operation.

major


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## marcelo2112 (Mar 29, 2016)

Thank you. Then I have to change all the mosfet.


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## marcelo2112 (Mar 29, 2016)

I ask the experts, what is the circuit that closes the main contactor? I have the code 3.4, change all the lm339 but I do not understand the circuit that activates the mosfet, where does the signal that activates it come from?


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