Overview

Design

General notes

Since the drives are operated in very different environments and additional electrical components (controllers, switched-mode power supplies, etc.) can differ greatly with regard to interference immunity and emitted interference, each installation guideline can only be a sensible compromise. In individual cases, therefore, after examination, deviation from the rules is possible.

To ensure electromagnetic compatibility (EMC) in your cabinets in an electrically harsh environment and to be able to meet the legal standards, the following EMC rules should be observed during design and installation.

Rules 1 to 10 are generally applicable. Rules 11 to 15 are necessary to meet the emitted interference standards.

Rules for electromagnetically compatible installation

Rule 1

All metal parts of the cabinet must be joined to each other with good electrical contact (not paintwork on paintwork!). Contact or toothed washers should be used where necessary. The cabinet door should be connected to the cabinet via ground straps (at top, middle and bottom) with as short a path as possible.

Rule 2

Contactors, relays, solenoid valves, electromagnetic operating hours counters, etc. in the cabinet and if necessary in adjacent cabinets, should be provided with suppression combinations, such as RC networks, varistors or diodes. The circuitry must be implemented directly at the particular coil.

Rule 3

Signal lines 1) should be routed into the cabinet from one level if possible.

Rule 4

Unshielded conductors of the same circuit (outgoing and return conductors) should be twisted together if possible, i.e. the surface between outgoing and return conductors should be kept as small as possible to prevent the creating of unnecessary frame antennas.

Rule 5

Spare cores should be connected to the cabinet ground ²⁾. This achieves additional shielding.

Rule 6

Unnecessary line lengths should be avoided. Coupling capacitances and inductances are thus kept low.

Rule 7

In general, crosstalk is reduced when conductors are placed close to the cabinet ground. Wiring should, therefore not be placed in free space in the cabinet but, wherever possible, routed closely along the cabinet housing or installation plates. This also applies to spare cables.

Rule 8

Signal lines and power cables should be laid separately from each other (to avoid coupling paths). A minimum clearance of 20 cm is desirable.

If segregation between sensor cables and motor cables is not possible, the sensor cable should be decoupled by a partition plate or by installing it in a metal conduit. The partition plate or metal conduit should be grounded at several points.

Rule 9

The shields of digital signal cables should have good large-area electrical grounding at each end (source and destination). In the event of poor equipotential bonding between the shield connections, an additional equalizing conductor of at least 10 mm² should be laid in parallel with the shield to reduce the shield current. In general, shields may be connected to the cabinet housing (ground) at several points. Even outside the cabinet, the shields may be connected in several places.

Foil shields are not satisfactory. Compared to braid shields, their shielding effect is inferior by a factor of at least 5.

Rule 10

With good equipotential bonding, the shields of analog signal lines may be grounded at both ends (with good large-area contact)!). Good equipotential bonding can be assumed if all metal parts make good contact and the electronic components involved are powered from the same power supply.

Single-ended shield grounding prevents low-frequency capacitive interference pickup such as 50 Hz hum. The shield connection should be made in the cabinet; a sheath wire may be used to connect the shield.

Rule 11

Positioning the radio interference suppression filter in the vicinity of the suspected interference source: The filter should be mounted with its surface on the cabinet housing, mounting plate, etc.. Input and output leads should be separated.

Rule 12

The use of radio interference suppression filters is mandatory for compliance with limit value class A1. Additional loads should be connected ahead of the filter (supply system side).

The need to install an additional line filter depends on the controller in use and on the type of wiring of the rest of the cabinet.

Rule 13

With a regulated field current supply, a commutating reactor is needed in the field circuit.

Rule 14

A commutating reactor is needed in the armature circuit of the converter.

Rule 15

With SIMOREG drives, the motor cables may be unshielded.

The supply cable must have a clearance of at least 20 cm from the motor cables (field, armature). A partition plate should be used if necessary.

¹⁾ Signal lines are defined as:
Digital signal line:
Lines for pulse generators
Serial interfaces, e.g. PROFIBUS-DP
or analog signal line
(e.g. ±10 V setpoint line).

²⁾ The definition of ground, in general, encompasses all metallic conductive parts which can be connected to a protective conductor, e.g. a cabinet housing, motor housing, foundations earth, etc.

Cabinet arrangement and shielding

The cabinet arrangement is intended to draw the user's attention to the EMC-critical parts. The example does not necessarily show all possible cabinet components or arrangements.

Details affecting the interference immunity and emitted interference of the cabinet and which do not clearly appear in the block diagram are shown in the Figures.