DC Motor controller

[mhtavallaie]

dear friends

anybody willing to provide me with a simple practical circuit which controls A DC brached Motor is highly welcome.

The circuit must work with 220VAC

RGDS
hadi

 

[Styx]

what kind of control?

position?
torque?
speed?

 

[Russlk]

How much horsepower or current draw?

 

[Styx]

Well he has just Private messaged me with this info:

I am looking for an speed cntrlr and the motor rating as around 100watt

SO basically a speed loop and also a current loop, But again no where near enough infomation. The power is there, but not maximum speed that would state the maximum torque=> current. Also no info on ouptut characteristics.


No mention of what you are using to sense the speed of the machine,

 

[Russlk]

Is it a 220 VDC motor?

 

[Styx]

I have had another couple of PRivate messages (mhtavallaie, im trying to keep this public just incase I am missing something)

the motor maximum ratation speed is L.T 150 r/min the voltage around the anchor is around 200VDC and the field max voltage is 210v DC

Still missing info.

Are you after a really simple speed control
open-loop, via varying terminal voltage

Simple closed-loop
via closing the voltage loop and basing the speed control on the w=k*V

True close-loop
using a speed sensor.


Only the last one will adapt to changing load
plus are you expecting a working ciruit or do you have one that you are having problems with?

 

[mhtavallaie]

DC mot cntrlr

Hi Mr. Styx

I don't need any speed sensor a simple closed loop will do the job.

as I mentioned in my previous reply I am using bridges and triac but It is not functioning properly

rgds
hadi

 

[Styx]

Fair enough, for a brushed motor, voltage control will give a fairly stable form of speed control.

You say from AC? The easiest way would be to use a Thyristor bridge to make a "controlled rectifier" and thus vary the DC-link feeding the motor (big DC-link cap).

Using a simple voltage loop to change the firing angle based on the present voltage error (Voltage demand - voltage feedback).


What circuits have you tried. It sounds like you have recified the AC and then used a H-brisge to chop it down.

Can you post what you have done.

Still a phase-control thyristor rectifier would be the better option

 

[mhtavallaie]

Dc Mot Cntrlr

Dear Mr. Styx

many thanks for your patience that you are still pursuing the subject.


As I mentioned I have used a normal bridge rectifier which directly converts 220VAC to equivalent DC voltage needed for anchor and a dimmer using a BT138 triac and poti provides the field volage ( dimmer output bieng rectified by another bridge before being applied to the field)

with this circuit i have visible sparks over the collector , motor gets hot and triac burns out after a couple of weeks working .

rgds
hadi

 

[Styx]

you have got a free-wheel diode dont you?

could you post the circuit please