TDA 1085C Microcontroller for speed of asink. motor

[Vraana1]

Hi,

My name is Nedjeljko; I have one problem with this regulator of speed for asynchrony motor:

I use two regulators for two different motors. 1st motor is 0.75 kW, 2nd is 1.8 kW – Regulation goes with potentiometer 0-50kΩ.

1st motor works correctly without problems, but 2nd motor have problems with stability of speed – that problems is when I put potentiometer to half value (cca. 25kohms..Or any other value then min or max)!
Motor then works on way that speed of it goes from minimum to maximum periodically.

Please help me if someone knows something about this!
If you need more information I will send you, but please help me in this case, I must to finish object next week, so I need to make and this part of regulation.

my mail: [email protected]
Thanks