Uninterruptible Power Supply
White Paper #1
The Different Types of
UPS Systems
Revision 5
By Neil Rasmussen 2003 American Power Conversion. All rights reserved. No part of this publication may be used, reproduced, photocopied, transmitted, or stored in any retrieval system of any nature, without the written permission of the copyright owner. www.apc.com Rev 2004-5
2
Executive Summary
There is much confusion in the marketplace about the different types of UPS systems and their characteristics. Each of these UPS types is defined, practical applications of each are discussed, and advantages and disadvantages are listed. With this information, an educated decision can be made as to the appropriate UPS topology for a given need. 2003 American Power Conversion. All rights reserved. No part of this publication may be used, reproduced, photocopied, transmitted, or stored in any retrieval system of any nature, without the written permission of the copyright owner. www.apc.com Rev 2004-5
3
Introduction
The varied types of UPSs and their attributes often cause confusion in the data center industry. For example, it is widely believed that there are only two types of UPS systems, namely standby UPS and online UPS. These two commonly used terms do not correctly describe many of the UPS systems available.
Many misunderstandings about UPS systems are cleared up when the different types of UPS topologies are properly identified. UPS topology indicates the basic nature of the UPS design. Various vendors routinely produce models with similar designs, or topologies, but with very different performance characteristics.
Common design approaches are reviewed here, including brief explanations about how each topology works. This will help you to properly identify and compare systems.
UPS types
A variety of design approaches are used to implement UPS systems, each with distinct performance
The Different Types of
UPS Systems
Revision 5
By Neil Rasmussen 2003 American Power Conversion. All rights reserved. No part of this publication may be used, reproduced, photocopied, transmitted, or stored in any retrieval system of any nature, without the written permission of the copyright owner. www.apc.com Rev 2004-5
2
Executive Summary
There is much confusion in the marketplace about the different types of UPS systems and their characteristics. Each of these UPS types is defined, practical applications of each are discussed, and advantages and disadvantages are listed. With this information, an educated decision can be made as to the appropriate UPS topology for a given need. 2003 American Power Conversion. All rights reserved. No part of this publication may be used, reproduced, photocopied, transmitted, or stored in any retrieval system of any nature, without the written permission of the copyright owner. www.apc.com Rev 2004-5
3
Introduction
The varied types of UPSs and their attributes often cause confusion in the data center industry. For example, it is widely believed that there are only two types of UPS systems, namely standby UPS and online UPS. These two commonly used terms do not correctly describe many of the UPS systems available.
Many misunderstandings about UPS systems are cleared up when the different types of UPS topologies are properly identified. UPS topology indicates the basic nature of the UPS design. Various vendors routinely produce models with similar designs, or topologies, but with very different performance characteristics.
Common design approaches are reviewed here, including brief explanations about how each topology works. This will help you to properly identify and compare systems.
UPS types
A variety of design approaches are used to implement UPS systems, each with distinct performance