VBR Load Analyzer
The Powerohm Variable Braking Resistor Analyzer will determine what braking resistor ratings are required for your specific application. The Powerohm VBR is a portable test unit that provides selectable steps of resistance for analyzing your braking requirements for a wide range of drive horsepowers. Simply connect the VBR to your drive or braking module and let the application decide what braking resistor it needs. Once you determine the optimal resistance value for your drives peak performance, the VBR’s digital readout will accurately display the true duty cycle as the application runs.
Have you ever had a startup and realized the application needs a braking resistor? The Powerohm VBR can also be used as a temporary solution, providing instant braking for your installation. Keep the unit in place while you wait for its permanent replacement.
An additional benefit is the ability to determine whether a braking resistor can improve process times of an existing application. Drive deceleration times are limited without a braking resistor and the VBR is just the device to determine if improvements can be made with the simple addition of a resistor.
Step 1: Secure the VBR unit in place and plug in supplied power cord to a 120VAC source before connecting load leads to drive or braking module. Attach the supplied load lead cables to the drive by connecting the red and black cables to the drive’s braking resistor terminals. (BR+, BR- or BR1, BR2) Warning: Drive power and DC bus must be OFF before connecting the loads leads.
Step 2: Turn power selector switch to the ON position to activate the VBR unit. The selector switch should illuminate green and blowers should function when ON. Insure that there is a minimum clearance of 24 inches beyond the exhaust to any non-flammable surfaces.
Step 3: If the drive has an existing braking resistor installed, it is important to not press the “Braking Enable” pushbutton. Enabling a selected resistor value may push the equivalent resistance below the minimum allowed. Note that the VBR can be used to analyze an existing braking resistor to determine if a more effective resistor could be used for the installation (skip to Step 5 if this is the case).
Step 4: Select a desired resistance value and press “Braking Enable” to activate the resistive load. It is critical that the resistance value selected is greater than the minimum resistance value specified by the drive or braking module manufacturer. Selecting a resistance value lower than the minimum may cause permanent damage to the drive or braking module.
Step 5: Start and run the Drive at full load, through it’s entire motoring and braking cycles for a minimum of 30 minutes. To prevent under sizing the resistor, be sure to operate at maximum load in combination with the most sever duty cycle. During the cycling of the Drive you will notice that “VBR Reading” will begin to register a readout from 1 to 135.
Step 6: It is important to run the Drive a minimum of 30 minutes so that the proper watt selection of the resistor is realized. At this time the “VBR Reading” should have reached its maximum value and you are you are ready to record the peak “VBR Reading.” Lift off the small cover below the digital readout to access the programming keys. Press the up arrow key - the second key from the left. This blinking number displayed is the peak readout that will be used in sizing your braking resistor.
Step 7: With the resistance value you selected in Step 4 (or the value of an existing braking resistor) and the peak “VBR Reading” you recorded from Step 6, you now have all the data necessary to perfectly size a braking resistor for your application.
Step 8: The VBR unit must remain ON a minimum of 5 minutes after the drive is powered down to allow the unit to cool. Do not remove load leads until the Drive and DC bus power is OFF. Use caution when handling the VBR