Im having issues with pulsing on the low speed ranges , the PCB runs a 180v DC motor fitted to a converyour on a sanding machine.I have tested another machine and it runs smoothly throughout the speed range.(no pulsing)

I have carried out basic testing by unsoldering the trim pots , diodes , capacitors and all seem to test out OK.(ohms test on trim pots / diode setting on meter / farads and ESR test using cap tester / replaced SCR aswell)

input to PCB = UK / 230V / 50 HTZ.
PCB to run a 180VDC MOTOR / 130W.
correct speed for conveyor at low is 35VDC and high is 145VDC.

*I assume this is a phase angle control type PCB ? (I would welcome confirmation for this)

*I would very much any help on the next steps to help fix the pulsing issue.

Thanks Aspiespot.

 

130w is quite low for a conveyor motor, it may be worth looking into a PWM style controller, they usually control down to low rpm without the LF pulsed control of a triac.
Max.

 

Im having issues with pulsing on the low speed ranges , the PCB runs a 180v DC motor fitted to a converyour on a sanding machine.I have tested another machine and it runs smoothly throughout the speed range.(no pulsing)

I have carried out basic testing by unsoldering the trim pots , diodes , capacitors and all seem to test out OK.(ohms test on trim pots / diode setting on meter / farads and ESR test using cap tester / replaced SCR aswell)

input to PCB = UK / 230V / 50 HTZ.
PCB to run a 180VDC MOTOR / 130W.
correct speed for conveyor at low is 35VDC and high is 145VDC.

*I assume this is a phase angle control type PCB ? (I would welcome confirmation for this)

*I would very much any help on the next steps to help fix the pulsing issue.

Thanks Aspiespot.

Its half wave phase control meaning the pulses are only every 20mS. My guess would be the two sanders differ in the motor inertia, more inertia will smooth out the pulses at low rpm, it could also be different motor-belt reduction ratio's.. I am afraid there is little you can do with your existing controller and as MAX sugested you need a high frequency PWM drive to get any improvement, that may be more expensive than buying another of the sanders that works!

Of course if you just want to stop it reaching the lumpy speed you can adjust the presets to limit the control knob range.

 

Its half wave phase control

Conversion to full-wave control should improve things.
BTW, be aware that the circuit shown does not provide isolation from the mains, so touching any part of the circuit coud be hazardous.

 

Conversion to full-wave control should improve things.
BTW, be aware that the circuit shown does not provide isolation from the mains, so touching any part of the circuit coud be hazardous.

Thanks for your replies , So for my own learning when 1 SCR is used on a PCB it would normally be half wave and when 1 Triac is used on a PCB its normally full wave ?
I think I will look into sourcing a PWM Board,

 

So for my own learning when 1 SCR is used on a PCB it would normally be half wave and when 1 Triac is used on a PCB its normally full wave ?

If one SCR is inside a full-wave rectifier bridge it could provide full-wave control.