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Designing Electronic starter for DC motor

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sharpuee

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I have to develop an electronic starter for 230 V, 2HP DC motor as my B.Tech project. After rectification of initial power, I am using MOSFET to control the armature voltage through PWM technique. The whole problem is to control armature current by applying gradually increasing voltage at the time of starting. I don't know which technique would be best for this purpose. For MOSFET control, Some advice to use 555 ramp generator along with comparator, some say to use op-amps only and some say to go for digital timers. Is PWM best technique for this or some better technique is there ?? Will these controllers be able to drive MOSFET connected in 207 V DC power circuit???? Please help me with the power and controller circuit design ..
 

tcmtech

Banned
Most Helpful Member
It may be easier to use a pair of SCR's in the rectifier bridge. Using simple phase control is the easiest way to control DC motors running off of AC power sources. Using opto coupled SCR drivers would alow you complete isolation from the main lines But still give you total control over each part of the incoming AC cycle.
 

Diver300

Well-Known Member
What is it with projects and 555 timers? Use something modern, please!

PWM and MOSFETs would be fine but you will have to drive the MOSFET gates quite hard. SCRs would also be fine, and probably easier to drive.

Either way, current feedback would be a good idea. You can use a hall effect current transducer to keep the nasty voltages away from your fingers.

You need a microcontroller to do all the control. I've worked on circuits that controlled DC motors, and used op-amps and discrete components to do the control. The boards were 400 mm square. In a microcontroller, all your timing an ramp functions can be done with no extra components, and all the extras that you haven't thought about now can be programmed not soldered.
 

sharpuee

New Member
thank you diver300.. i have studied basics of microcontroller ... r u suggesting to use it for mosfet gate control or SCRs ??
can u provide me with details of how to do it with opamps and discrete components ... It would be nice if u can provide rough diagram of power ciruit and gate control if u can ...a rough sketch would work .. i am not getting which technique will be most efficient, effective and protective ??
 
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