Hello

My name is Kenis, I am electronic engineer, and I am working on developing of different projects for my clients.
One of my clients looks for system to control ventilation speed in buildings. I have found you work on frequency converter / frequency inverters (I really don't know proper English name of unit I need). So maybe let me describe what I need. Client need to control speed of fan motor to change ventilation in buildings. The motor's power will be 1.5kW up to 15 kW, 3 phase, polish voltage (230V / 380V; 50Hz). Whole installation it will be CAN 2.0b controlled.
So for now I am looking for frequency converter capable to control fan speed.
I am not familiar with motor speed control methods, but client said that for such application models with advanced parameters such as acceleration, soft starts and etc. it will be not necessary, and it will only increase final price. So I am looking for quite cheap, simple frequency converter I could use in application, and another question is if there is CAN control interface available for unit, and what is the difference with price between with or without CAN interface version (depends on the price, adding CAN interface it will be my work)