SSD 605C Product Manual - Cabling Requirements

12-2  

Certification for the Inverter

605C Frequency Inverter

Control and signal cables for the encoder, all analog inputs, and communications require

screening with the screen connected only at the VSD end. However, if high frequency noise is

still a problem, earth screen at the non VSD end via a 0.1

µF capacitor.

Note:  Connect the screen (at the VSD end) to the VSD protective earth point, and not to the

control board terminals.

Cabling Requirements

Note:  Refer to Chapter 11: “Technical Specifications” for additional Cabling Requirements.

Planning Cable Runs

•  Use the shortest possible motor cable lengths.

•  Use a single length of cable to a star junction point to feed multiple motors.

•  Keep electrically noisy and sensitive cables apart.

•  Keep electrically noisy and sensitive parallel cable runs to a minimum. Separate parallel

cable runs by at least 0.25 metres. For runs longer than 10 metres, separation should be

increased proportionally. For example if the parallel runs were 50m, then the separation

would be (50/10) x 0.25m = 1.25m.

•  Sensitive cables should cross noisy cables at 90°.

•  Never run sensitive cables close or parallel to the motor, dc link and braking chopper circuit

for any distance.

•  Never run supply, dc link or motor cables in the same bundle as the signal/control and

feedback cables, even if they are screened.

•  Ensure EMC filter input and output cables are separately routed and do not couple across

the filter.

Increasing Motor Cable Length

Because cable capacitance and hence conducted emissions increase with motor cable length,

conformance to EMC limits is only guaranteed with the specified ac supply filter option using a

maximum cable length as specified in Chapter 11: “Technical Specifications”.

This maximum cable length can be improved using the specified external input or output filters.

Refer to Chapter 11: “Technical Specifications” - External Filters.

Screened/armoured cable has significant capacitance between the conductors and screen which

increases linearly with cable length (typically 200pF/m but varies with cable type and current

rating).

Long cable lengths may have the following undesirable effects:

•  Tripping on `overcurrent’ as the cable capacitance is charged and discharged at the

switching frequency.

•  Producing increased conducted emissions which degrade the performance of the EMC filter

due to saturation.

•  Causing RCDs (Residual Current Devices) to trip due to increased high frequency earth

current.

•  Producing increased heating inside the EMC ac supply filter from the increased conducted

emissions.

These effects can be overcome by adding chokes or output filters at the output of the VSD.