Installation Instructions · Publication DRIVES-IN001 · Rockwell Automation

Wiring and Grounding Guidelines for PWM AC Drives

This installation instructions publication from Rockwell Automation covers wiring and grounding for pulse-width modulated (PWM) AC drives. It addresses wire and cable selection, power distribution system configurations, grounding practices, EMI mitigation, reflected wave effects, and motor cable length restrictions. The document applies to PowerFlex 4, 4M, 40, 400, 520-Series, 70, 700, 700H, 700L, 700S, 753, 755, 755T, 1336 PLUS II, 1336 IMPACT, 1305, and 160 drives. It is intended for qualified personnel who plan and design PWM AC drive installations.

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PowerFlex 4 through 75… Drive Families Covered
DRIVES-IN001Q-EN-P, Ju… Publication Revision
≥15 mil Min. Wire Insulation Thickness
≥0.3 m Control Wire Separation from Power

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Specifications

Recommended Cable Design Types

Type 1: max wire size 2 AWG; 600V, 90 °C XHHW2/RHW-2; 4 tinned copper conductors with XLPE insulation
Type 2: max wire size 2 AWG; 600V, 90 °C RHH/RHW-2; 4 tinned copper conductors with XLPE plus one shielded pair of brake conductors
Type 3: max wire size 500 MCM AWG; Tray-rated 600V, 90 °C RHH/RHW-2; 3 tinned copper conductors with XLPE and 3 bare copper grounds, PVC jacket
Type 4: max wire size 500 MCM AWG; Tray-rated 600V, 90 °C RHH/RHW-2; for water/caustic/crush-resistance; Class I and II, Division I and II locations
Type 5: max wire size 500 MCM AWG; Tray-rated 2000V, 90 °C; 3 tinned copper conductors with XLPE and 3 bare copper grounds, PVC jacket; 690V applications

Temperature Rating Requirements

Ambient 50 °C (122 °F) Use 90 °C (194 °F) wire (required for UL)
Ambient 40 °C (104 °F) Use 75 °C (167 °F) wire (required for UL)
Wire gauge basis Requirements and recommendations based on 75 °C (167 °F) rating; do not reduce gauge when using higher temperature wire

Ground Conductor Configuration

Drives up to and including 200 Hp (150 kW) Cable with one ground conductor
Drives larger than 200 Hp (150 kW) Cable with three ground conductors, spaced symmetrically around power conductors
Ground conductor rating Must be rated for full drive ampacity

DH+ / Remote I/O Cable Length vs. Communication Rate

57.6 Kbps 3048 m (10,000 ft) maximum
115.2 Kbps 1524 m (5000 ft) maximum
230.4 Kbps 762 m (2500 ft) maximum

Recommended Signal Wire: Analog and Encoder

Standard analog I/O 0.750 mm² (18 AWG), twisted pair, 100% shield with drain; 300V, 75…90 °C
Remote pot 0.750 mm² (18 AWG), 3-conductor, shielded
Encoder/Pulse I/O < 30.5 m (100 ft) 0.196 mm² (24 AWG), individually shielded
Encoder/Pulse I/O 30.5…152.4 m (100…500 ft) Signal: 0.196 mm² (24 AWG) individually shielded; Power: 0.750 mm² (18 AWG)
Encoder/Pulse I/O 152.4…259.1 m (500…850 ft) Signal: 0.196 mm² (24 AWG) individually shielded; Power: 0.750 mm² (18 AWG); Combined: 0.750 mm² (18 AWG) individually shielded pair

AC Line Impedance Thresholds (General Rules)

Drives without built-in inductors: add line impedance when Transformer kVA > 10x drive kVA, or percent source impedance per drive < 0.5%
Drives with built-in inductors: add line impedance when Transformer kVA > 20x drive kVA, or percent source impedance per drive < 0.25%
Voltage imbalance threshold Use input line reactor when line voltage imbalances exceed 2%

Communication Protocols

Supported industrial networks and field buses for the products covered by this publication.

DeviceNet Four cable types supported: round thick (12.2 mm OD), round thin (6.9 mm OD), flat, and KwikLink drop cable. Round cable carries 5 wires: two twisted pairs (24V DC power and signal) plus a drain wire. See publication DNET-UM072. ControlNet Uses RG-6 quad shield coax cable; recommended catalog number 1786-RG6. Cable type selection depends on environment. See publication CNET-IN002. Ethernet Uses shielded twisted pair (STP) or unshielded twisted pair (UTP) cable with RJ45 connectors meeting IP67 standard. Shielded cable recommended for installations with welding, electrostatic processes, drives over 10 Hp, MCCs, high-power RF radiation, or devices carrying current exceeding 100 A. Remote I/O / Data Highway Plus (DH+) Only Allen-Bradley catalog number 1770-CD shielded twin-axial cable is tested and approved. Series or daisy chain topology only; star topology not permitted. All three connections (blue, shield, and clear) must be connected at each node. RS-232 One twisted pair plus one signal common. RS-485 Two twisted pairs, each individually shielded.

Document Contents

Full PDF covers the following topics in detail:

  • Preface
  • Chapter 1: Wire/Cable Types
  • Chapter 2: Power Distribution
  • Chapter 3: Grounding
  • Chapter 4: Best Practices
  • Chapter 5: Reflected Wave
  • Chapter 6: Electromagnetic Interference
  • Appendix A: Motor Cable Length Restrictions

Frequently Asked Questions

Which Allen-Bradley drive families does this publication cover?
The publication covers PowerFlex 4, 4M, 40, 400, 520-Series, 70, 700, 700H, 700L, 700S, 753, 755, and 755T drives, as well as legacy Bulletin 160, 1305, 1336 PLUS II, and 1336 IMPACT drives.
What wire material is required for Allen-Bradley drive terminal connections?
Only copper wire is permitted. The wire clamp-type terminals in Allen-Bradley drives are made for use with copper wire. Using aluminum wire can cause connections to loosen and lead to premature equipment failure.
When should shielded motor cable be used instead of unshielded cable?
Shielded cable is recommended for installations with sensitive equipment such as weigh scales and capacitive proximity switches, large numbers of drives in one location, imposed EMC regulations, or a high degree of communication and networking. Shielded cable can also help reduce shaft voltage and induced bearing currents, and may extend allowable motor-to-drive cable distance without additional motor protective devices.
What is the minimum wire insulation thickness required for drive installations?
Wire must have an insulation thickness of ≥15 mil (0.4 mm / 0.015 in.). The wire insulation must not have significant variations of concentricity around the wire. The minimum wire size for PVC cable with 20 mil or greater insulation is 10 gauge.
When is a line reactor or additional transformer recommended in front of a PWM drive?
A line reactor or transformer is recommended when the installation site has switched power factor correction capacitors, lightning strikes or voltage spikes in excess of 6000V peak, power interruptions or voltage dips in excess of 200V AC, or when the supply transformer is too large relative to the drive. For drives without built-in inductors, add impedance when transformer kVA exceeds 10 times drive kVA or source impedance per drive is less than 0.5%. For drives with built-in inductors, add impedance when transformer kVA exceeds 20 times drive kVA or source impedance is less than 0.25%.
What grounding system is recommended for PWM AC drive installations?
Rockwell Automation recommends grounded neutral systems, specifically Delta/Wye with grounded Wye neutral. This configuration provides a controlled path for common mode noise current, a consistent line-to-ground voltage reference that minimizes insulation stress, and accommodation for system surge protection schemes.
How should control wires be separated from power wires?
Control wires should be separated from power wires by at least 0.3 m (1 ft). Shielded multi-conductor cable is recommended for digital I/O to reduce cross-coupled noise from power cables. Analog signal wires and encoder cables should also be separated from power wires by at least 0.3 m (1 ft), and encoder cables should run in a separate conduit. When signal cables must cross power cables, they should cross at right angles.

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