RF Magnetic Noise Sheilding

[aarul]

I am trying to build a automated NDT device using an electromagnetic sensor (pulse receive system) driven in a single axis linear actuator by a Parker stepper motor. However, whenever the motor is switched on, the magnetic sensor picks up a noisy inteference.

The supply to the motor drive (Zeta 4)is filtered and the motor cage is earthed to the common point as the drive. The is no interefence when the drive is on by itself. The connection from drive to motor is screened too.

Similar noise pickup is observed when a servo motor is used. But with a DC motor, the noise level is down to acceptable limits?

Does anyone know what would be the type of noise, how sheilding can be done?

 

[jbartos]

Questions:
1. Do you run the magnetic sensor run in a separate conduit?
2. Do you filter high frequency content on the motor drive output (How good is the motor drive output filter in terms of filtering frequency bands?)?

 

[aarul]

hi bartos,

the magnetic sensor is mounted on a linear actuator driven by the stepper motor. There is a seperate amplifier that energises the sensor and receives the signal.

the supply filter that I am using is a stand line filter for mains power supply, for eliminating voltage spikes and to attenuate any noise from the mains.

cheers

 

[jbartos]

Question: Please, is the stepper motor shielded?

 

[aarul]

I have a shielded cable connection from the drive to the motor. The earth connection on the motor end is ground to the casing with the screen from the cable and the earth connection is also ground at the drive end with the screen open.

I am using a 240vac to 115 VAC stepdown transformer as power supply to the drive and motor. The line filter is between the transformer and drive and is ground to the casing of the drive.