VFDs: DB Minimum
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Dynamic Brake Resistor Selection

The selection of a dynamic brake resistor seems straight forward; however, there are important details to consider.  Two parameters must be specified to select a resistor, resistance (ohms) and power (watts).  The resistance determines the rate of which the resistor can absorb energy from the drive.  The power indicates how much energy can be absorbed during a finite amount of time.  Tables (below will specify the minimum resistance which can be connected to each drive based on drive model number.  Occasionally, a resistor can be reused from a previous drive; however, the minimum resistance must be check for the new drive.  DO NOT CONNECT A LOWER RESISTANCE TO A DRIVE THAN ALLOWED BY THE TABLE.

The power rating for a resistor is typically determined by its duty cycle.  This is calculated by looking at a ten minute time period.  During ten minutes, how many minutes will the drive be transferring energy to the resistor (regenerating).  Regeneration time divided by ten minutes will provide the duty of the resistor.  Higher duty resistors are physically larger, generate more heat, and are more expensive.  Call your drive specialist for discussion on the selection for complex applications.

 

PowerFlex 520-Series

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PowerFlex 750-Series

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