The following tables list the recommended and maximum possible cable connections at the line and motor ends for a single circuit connection (versions A and C) and a parallel circuit (version A).

The recommended cross-sections are based on the specified fuses. They are applicable for 3-wire cables manufactured out of copper with PVC insulation, routed horizontally in air and a permissible wire temperature of 70 °C (e.g. Protodur NYY or NYCWY) for an ambient temperature of 40 °C and individual routing.

When the conditions differ from those specified above (cable routing, cable grouping, ambient temperature), the appropriate correction factors according to IEC 60364-5-52 must be taken into account.

The SINAMICS Low Voltage Engineering Manual contains additional information and is available as a PDF file on the CD-ROM included with Catalog D 11.

Single circuit

1) The recommendations for the North American market in AWG or MCM must be taken from the appropriate NEC (National Electrical Code) and/or CEC (Canadian Electrical Code) standards..

Single circuit

1) The recommendations for the North American market in AWG or MCM must be taken from the appropriate NEC (National Electrical Code) and/or CEC (Canadian Electrical Code) standards.

Parallel cicuit

Note: The recommended and maximum conductor cross-sections relate to the appropriate subsystem of the converter connected in parallel circuit.

¹⁾ The recommendations for the North American market in AWG or MCM must be taken from the appropriate NEC (National Electrical Code) and/or CEC (Canadian Electrical Code) standards.

²⁾ The motor-side inverter comprises three Motor Modules connected in parallel.

Minimum motor cable lengths for operation with power units connected in parallel

When using power units connected in parallel, the following motor cable lengths must be observed if a motor is connected with only one winding system and no motor-side reactors or filters are used:

Required cable cross-sections for line and motor connections

It is always advisable to use shielded cables between the converter and motor and, in the case of drives in the higher output power range, symmetrical 3-wire, three-phase cables, and to connect several cables of this type in parallel where necessary. There are basically two reasons for this recommendation:

• This is the only way in which the high IP55 degree of protection can be achieved for the motor terminal box without problems because the cables enter the terminal box via glands and the number of possible glands is limited by the geometry of the terminal box. Therefore single cables are less suitable.
• With symmetrical, 3-wire, three-phase cables, the summed ampere-turns over the cable outer diameter are equal to zero and they can be routed in conductive, metal cable ducts or racks without any significant currents (ground current or leakage current) being induced in these conductive, metal connections. The danger of induced leakage currents and thus of increased cable-shield losses increases with single-wire cables.

The required cable cross-section depends on the amperage which flows through the cable. The permissible current loading of cables is defined, for example, in IEC 60364-5-52. It depends on ambient conditions such as the temperature, but also on the routing method. An important factor to consider is whether cables are routed singly and are therefore relatively well ventilated, or whether groups of cables are routed together. In the latter instance, the cables are much less well ventilated and might therefore heat one another to a greater degree. For the relevant correction factors applicable to these boundary conditions, please refer to IEC 60364-5-52.

The table below provides a guide to the recommended crosssections (based on IEC 60364-5-52) for PVC-insulated, 3-wire copper and aluminum cables, a permissible conductor temperature of 70°C (e.g. Protodur NYY or NYCWY) and an ambient temperature of 40°C.

Current carrying capacity according to IEC 60364-5-52 at 40 °C

¹⁾ Maximum 9 cables routed horizontally in direct contact with one another on a cable rack

With higher amperages, cables must be connected in parallel..

Note: The recommendations for the North American market in AWG or MCM must be taken from the appropriate NEC (National Electrical Code)/CEC (Canadian Electrical Code) standards.

Grounding and PE conductor cross-section

The PE conductor must be dimensioned to meet the following requirements:

• In the case of a ground fault, no impermissibly high contact voltages resulting from voltage drops on the PE conductor caused by the ground fault current may occur (< 50 V AC or < 120 V DC, IEC 61800-5-1, IEC 60 364, IEC 60 543).
• The PE conductor should not be excessively loaded by any ground fault current it carries.
• If it is possible for continuous currents to flow through the PE conductor when a fault occurs, the PE conductor cross-section must be dimensioned for this continuous current.
• The PE conductor cross-section should be selected according to EN 60 204-1, EN 60 439-1, IEC 60 364.

Note: The recommendations for the North American market in AWG or MCM must be taken from the appropriate NEC (National Electrical Code)/CEC (Canadian Electrical Code) standards.

• Switchgear and motors are usually grounded via separate local ground connections. When this grounding arrangement is used, the current caused by a ground fault flows through the parallel ground connections and is divided. Despite the use of the relatively small PE conductor cross-sections specified in the table above, no impermissible contact voltages can develop with this grounding system. Based on experience with different grounding configurations, however, we recommend that the ground wire from the motor should be routed directly back to the converter. For EMC reasons and to prevent bearing currents, symmetrical 3-wire three-phase cables should be used where possible instead of 4-wire cables, especially on drives in the higher power range. The protective or PE conductor must be routed separately when 3-wire cables are used or must be arranged symmetrically in the motor cable. The symmetry of the PE conductor is achieved using a conductor surrounding all phase conductors or using a cable with a symmetrical arrangement of the three phase conductors and three ground conductors. The SINAMICS Low Voltage Engineering Manual contains more detailed information on this topic and is available as a PDF file on the CD-ROM included with Catalog D 11.
• Through their controllers, the converters limit the load current (motor and ground fault currents) to an rms value corresponding to the rated current. We therefore recommend the use of a PE conductor cross-section analogous to the phase conductor cross-section for grounding the converter cabinet.