A variable frequency drive (VFD) is a critical component in motion control applications, providing a motor or load with a high level of speed control and diagnostics that an across-the-line motor starter or soft starter is unable to. The below flowchart, developed by AWC automation engineers and subject matter experts, can be used to easily identify the best Siemens VFD family for a particular application. Note: all rated HP values listed are based on Low Overload (Variable Torque applications)
The below table below provides an overview of each of Siemens’ SINAMICS VFD families included in AWC’s Design Assurance program. Please note that the attributes shown in the table are what are included within the scope of the Design Assurance program, not the complete range of the products.
The National Electrical Manufacturers Association (NEMA) has developed and maintained a standard set of definitions for various types of electrical enclosures found in industrial applications. Each type reflects certain levels of environmental conditions and personal protection against hazardous situations such as flying debris. The following tables 1, 2, and B-1 can be used as reference in determining the correct NEMA enclosure type for an indoor or outdoor application; the definitions of each type are outlined in NEMA Standard Publication 250 “Enclosures for Electrical Equipment (100 Volts Maximum)” and can be found HERE.
NEMA Enclosure Types
Table 1 – Comparison of Specific Applications of Enclosures for Indoor Nonhazardous Locations
Table 2 – Comparison of Specific Applications of Enclosures for Outdoor Nonhazardous Locations
Table B-1 – Comparison of Specific Applications of Enclosures for Indoor Hazardous Locations
(Note: if the installation is outdoors and/or additional protection is required by Tables 1 or 2, a combination-type enclosure is required)
In contrast to NEMA, whose standards apply within North America, the International Electrotechnical Commission (IEC) has developed their own set of standards (IEC 60529) which are defined by the degree of protection provided by the enclosure. The IEC designations are identified by the letters “IP” (Ingress Protection, followed by two numerals, as detailed below:
IEC Enclosure Classification Designations (IP Ratings)
These IEC enclosure designations do not take into consideration the risk of explosions, damage of mechanical equipment, or environmental factors such as moisture; for that reason, NEMA enclosure types cannot directly be equated to IP ratings. However, the following table A-1 can be used to convert NEMA enclosure type ratings to a comparable IP rating.
Table A-1 – Conversion of NEMA Enclosure Type Ratings to IEC 60529 Enclosure Classification Designations (IP)
(note: This table cannot be used to convert IEC Classification Designations to NEMA Type Ratings)
Sources: NEMA Enclosure Types (nema.org), Siemens Industrial Controls Catalog 2010
