How to Troubleshoot Error Over Current (EOC) Fault – F5 Elevator Drive

This article explains how to troubleshoot over current faults on a KEB F5 drive and diagnose the cause of the EOC fault. In short, this error indicates that the drive has exceeded the maximum allowable current.

For each scenario, there will be a checklist of steps to take when experiencing the EOC fault. Each checklist is accompanied by a brief description.

Refer to the specific scenario that pertains to your troubleshooting needs. For any scenario not listed in the article, please contact KEB technical support for further assistance.

Experiencing Error During Initial Start Up

If the car has never run before, there could be issues with motor data, encoder data, mechanical problems, or a combination of these. When using the term “run,” this means the car is operating controlled in both directions. All troubleshooting assumes that job-specific data has been entered into the drive and any required motor and encoder learns have been completed.

Car Has Never Run

1. Check motor data
   • Verify the drive motor data matches with the motor nameplate (LM01-07/LF10-17)
   • Verify that the motor pole count is close to a whole-even number
   • Redo the motor learn if any motor data has changed

2. Check encoder data
   • Verify the drive encoder data matches with the encoder (LE01-02/LF26-27)
   • Check for encoder movement (PM Motors only)
     1. If there is movement of over 2000 counts, change encoder channels (LE04/LF28) and redo encoder learn
     2. If car still does not run, then redo the encoder learn and see if there is too much encoder movement
     3. If the encoder position deviates too much, the motor data might be incorrect, the encoder may be mounted improperly, or the encoder may need to be replaced

3. Check to see if the drive transistors are shorted
   • Two options
     1. Perform the transistor test at end of this article or in the drive manual
     2. Default the keypad by changing the motor type to induction geared and run the car in open loop with the motor leads removed from the drive. (This is not recommended for PM motors, but can be done)
   • If the transistor test fails or the drive shows the same error with the motor leads off, then the transistors are shorted and the drive needs to be repaired or replaced
4. Check for mechanical issues
   • Verify that nothing is holding the motor back
     1. Brakes
     2. Rope Gripper
     3. Governor
     4. Safeties
     5. Other mechanical devices on the elevator

The motor nameplate should reflect the motor data input on the drive. The drive will use this to calculate the number of motor poles.

If everything on the drive looks normal and the parameters are correct. Then the last thing to check are mechanical issues.

Getting Fault Running Inspection

1. Check to see if the current is high
   • Check current on the Home Screen/LF93
     1. If the current is high in both directions, then refer to Car Has Never Run Section
     2. If current is high in one direction, then check counterweighting
   • Check to see if the elevator is balanced properly
     1. Put balanced load in the elevator and check current
        1. Current should be low and almost the same in both directions
        2. If not, then remove and add weight to car until the current is corrected
           1. Adding weight to car is the same as taking out weight of counterweight
           2. Taking off weight from car is like adding weight to counterweight

• • If this happens at the end of the run when brakes drop
    1. This is a mechanical issue with the brake dropping while the motor is still slightly moving
       1. This cannot be fixed on the drive, this is a timing and mechanical issue
          1. Consult with the controller OEM for further steps

Getting Fault Running Automatic

1. Check current on inspection and if the car is balanced
   • Refer to Getting Fault Running Inspection
2. Reduce amount of load put on drive during acceleration and deceleration phase of S-Curve
   • Lower acceleration or deceleration rates
   • Adjust counterweighting
   • Lower contract speed

If the error is happening right away when the car initially takes off, then there is another issue. Refer to Getting Fault Running Inspection section to see if the current is too high.

Getting Fault During 125% NTS Test

1. Reduce amount of load on drive due to higher amount of load
   • Lower deceleration rate
   • Add weight to counterweight
2. Call KEB Technical Support

Call KEB technical support for further assistance. If the car does not run with acceptable current in automatic and/or inspection, refer to the previous scenarios.

Experiencing Error on Existing Units

In this scenario, the elevator has been running in either inspection or automatic mode with acceptable current. Then, the car shuts down and the error is on the F5 drive. Since the elevator has been running, the data in the F5 drive should be correct. If the data were incorrect, then the car would have never been able to run.

Please note that the parameters are stored on the keypad. Since the issue most likely does not involve incorrect parameters, it is best to preserve them. If the drive needs to be replaced or repaired, keep the keypad and install it on the new drive. Then, load all the parameters onto the new drive. Depending on the age of the software on the keypad, it might not be possible to load the original keypad. However, the keypad will still power up and the parameters can still be read.

Getting the Fault Immediately When Trying to Run

1. Check to see if the drive transistors are shorted
   • Two options
     1. Perform the transistor test at the end of this article or in the drive manual
     2. Default the keypad by changing the motor type to induction geared and run the car in open loop with the motor leads removed from the drive. (This is not recommended for PM motors, but can be done)
   • If the transistor test fails or the drive shows the same error with the motor leads off, then the transistors are shorted and needs to be replaced or repaired
2. Check for mechanical issues
   • Verify that nothing is holding the motor back
     1. Brakes
     2. Rope Gripper
     3. Safeties
     4. Other mechanical devices on the elevator

3. Check to see if there are any electrical issues
   • Check for loose connections
   • Check motor to see if shorted
     1. Phase to phase resistance, should be low and balanced
     2. Phase to ground resistance, should be OL or high value
     3. If resistance readings are inconclusive, then Meg the motor

When the fault occurs immediately, it could be due to the failure of the output transistors on the F5 drive or something mechanical obstructing the motor from spinning.

To verify if the output transistors on the drive are shorted, you can perform a transistor test. This test requires a multimeter with a diode check feature, and the drive must be powered down. The test procedure and expected results will be provided at the end of this message. If the measured values differ from the expected ones, it indicates that the drive transistors are shorted, and the drive will need to be replaced or repaired.

Another method involves changing the motor type on the drive to induction geared in US03/US10 (LCD/LED) and loading the configuration in US05/US04 (if the motor type is not already induction geared). Then, change the control mode to option 0: Open Loop V/Hz in LC01/LF30. After this, remove the motor leads in the drive (UVW) and attempt to run the motor. If the drive still indicates “Error Overcurrent,” it means the transistors are shorted. If a different error appears on the drive, the transistors are not shorted. This test will help determine if the transistors are shorted. Note that this method is not recommended for permanent magnet motors because it will reset all the parameters to default values.

Transistor Test

In order to test the output transistors, you will need a multimeter with the diode check feature. Refer to Figure 1 above or follow the instructions in the video below to learn where to place your motor leads and to see the expected results for the size drive you have. To determine the housing size of the drive, check the KEB part number. For example, in the part number 20F5A1H-RLPB, the housing size is denoted by the bold 7th letter ‘H’.

For a video of the test being conducted, please refer to the video above.

KEB Elevator Support

We have been a leader in elevator drives for over 20 years and committed to providing top-notch products and industry-leading technical support. If you have any further questions, please don’t hesitate to contact us.