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Applications and How-Tos

How to Replace a Blown Fuse | R6 Regen Units

Jake Wattenphul | September 28th, 2023

This article is a step-by-step guide to inspect and replace a blown fuse in an R6 Regen unit.

Design and Purpose of the R6

The R6 regen unit converts otherwise wasted energy from an elevator or hoist system and commutates this energy back into electrical energy for other loads to consume. This regenerated electricity feeding back onto the grid improves the efficiency of the elevator or hoist application by reducing the amount of energy needed for the application as a whole.

KEB offers a size 15 for small applications and a size 19 for large applications.


R6 line regen units


Common Reasons for a Blown Fuse

During operation, unexpected power events resulting in voltage or current spikers may blow the R6 regens internal fuses. The fuses may also blow due to a short within an F5 drive or R6 regen unit itself.


How to Diagnose a Blow Fuse

The R6 regen can be wired in two different ways; Scheme A and Scheme B.


KEB R6 Regen Wiring Diagram with incoming power to the F5 drive through the Regen Unit
R6 Regen Wiring Diagram – Scheme A


Wiring Diagram of a KEB R6 Regen setup through the output of a F5 drive
R6 Regen Wiring Diagram – Scheme B


In scheme A, the F5 drive is powered by the regen. In scheme B, the F5 drive has three-phase power going into it. If a fuse in an R6 wired in scheme A is blown, the F5 drive will not turn on. If wired in scheme A and a fuse is blown, both the regen and the drive will power up, but the drive will have an error overvoltage fault (E. OP).


How to Replace an R6 Fuse

The following steps will help you replace an R6 regen unit’s fuses.

Step 1

Disconnect the regen unit from power and wait at least five minutes before servicing the regen unit. The disconnection allows for the DC bus capacitors to discharge safely.


Step 2

Remove the top cover of the regen unit by removing the keypad operator, the X2A terminal strips, the sync cable, the regen cover screw, and finally the two strain relief bar screws. Gently lift the top of the cover place and remove it from the body of the regen unit.

Info on Types of Fuses

The fuses are now visible within the regen unit. If either of the fuses are blown on the regen unit, a tab will lift on the bottom of the fuse. It is possible for only one fuse on the regen unit to blow and not the other.

Comparison of a Good fuse and a blown fuse for a KEB R6 Regen Drive
Comparison of a Good fuse (left) and a blown fuse (right) for a KEB R6 Regen Drive


When using a size 15 regen unit, a 600 V / 50A (part number 00.90.25H-3459) must replace the fuse. If using a size 19 regen unit, a 600 V / 125A (part number 00.90.25H-3559) must replace the fuse.

Step 3

If a fuse is bad, the next step is to remove the control card of the R6 unit. The control card is removed by unscrewing the card’s mounting screw found on the top of the unit. The card must then be carefully lifted from the unit with attention not to bend the connecting pins on the bottom of the control card. Next, unplug the fan from the control card and remove it from the housing shell.

Step 4

Remove the regen unit’s plastic housing. To remove the plastic housing of the regen unit remove the screw on the top of the regen unit. Gently lift the housing off its mounting tabs and lift. There are four mounting tabs on the regen unit, two on the top and two on the bottom. You may need to use a screwdriver to pry up the mounting tabs to get the plastic housing off.

Step 5

Remove the two fastening screws of the damaged fuses from the regen unit using a 6mm hex key. Then, remove the damaged fuses, replace them with new ones, and fasten them to the regen unit.

Step 6

Replace the plastic housing of the regen unit. Replace the plastic housing fastening screw and plug the fan into the control board.

Step 7

Slide the control card back into the regen unit, careful not to bend the pins on the bottom. Replace the screws fastening the control card, and then place the unit’s top cover back on.

Step 8

Replace the three screws on the top cover, the sync cable, the X2A terminal strips, and the keypad operator back on the unit.

Step 9

Finally, perform a diode check on both the regen unit and the drive unit.


Diode Check for an R6 Regen drive
After replacing the fuses, perform a diode check on your R6 regen unit


A diode check ensures no internal damage to the drive or the regen unit has occurred. Watch the video above for the specifics. If the diode check reads between 0.300 and 0.400, the R6 Regen diodes are still good. Now, you’re ready to power up the drive. If you have any questions, feel free to contact us!

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