Power 70 & 700 AC Drives, "External Brake Resistor"

Date: July 2002
Ref: CPAG 2002-07-003

Dear Rockwell Automation Customer:

The purpose of this letter is to inform you of a potential safety issue with the PowerFlex 70 and 700 AC drives when used with external brake resistors.

Identified shipments include:

PowerFlex 70 and 700 AC drives of all power ratings.

Problem Description

The optional internal brake resistors for the PowerFlex 70 and 700 drives are inherently self-protected to prevent drive damage due to resistor overheating. Since external braking resistors may not offer protection, additional precautions must be taken. When using non-self-protected external braking resistors with PowerFlex 70 and 700 drives, additional protection circuitry must be added to prevent brake resistor overheating and subsequent potential fire hazard. An example of this circuitry can be found in the attached schematic.

The requirement for resistor overheat protection must be considered for all drive installations where non-self-protected external resistors are used.

Product Identification

This Safety Alert affects all PowerFlex 70 and 700 AC drives with the following product catalog numbers:

Catalog Numbers
20AB…
20AC…
20AD…
20AE…
20BB…
20BC…
20BD…

Requested Customer Action

Each notified customer should perform the following actions:

Read the Product Safety Alert.

Confirm that they have the affected product.

If unprotected external brake resistors are used, implement the protection circuitry. (See attached schematic.)

If you need assistance, please call Allen-Bradley's Technical Support Group at (262) 512-8176.

We require and appreciate your immediate cooperation in this matter. If you have any questions regarding this Safety Alert, please contact our Technical Support Group at (262) 512-8176.

Respectfully,

Steve Perreault
Product Manager, PowerFlex 70 Drives
Rockwell Automation

Glenn Frazier
Product Manager, PowerFlex 700 Drives
Rockwell Automation