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Date: July 2002 Ref: CPAG 2002-07-003
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 schematic below.)
- 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.
Included Schematic:
