Trouble with DS18B20 and Power Flex 525

Hi every one.
I'm making a project to control a 3phase 2.2 HP motor with an Arduino Uno and a DS18B20 temperature sensor. I had conected the DS18B20 to the Arduino Uno, Arduino Uno to a Op-Amp to control the PowerFlex 525 to control the motor. The Arduino has a ModBus shield to comunicate with a PC.
The sensor reads and sends the temperature to the Arduino, the Arduino makes a PID calculation and send a ON and a PWM signal to the PowerFlex to control the speed of the motor.

My problem is that everything works great until the motor starts, then the sensor starts to read -127 °C and never change until the motor is off.
I don't know if the problem is Electro Magnetic Interference from the motor or maybe some uA current that filters from the PowerFlex becouse the GND it's common for all the divices, including the ModBus network.
I have a 1uF condenser/capacitor in the sensor, between VCC and GND of the DS18B20, but still doesn't work with the motor ON.

I would appreciate if some one could help me and give some ideas to solve this problem. Best regards.