Linear drive only moves in one direction - Causes & Solutions

1. Symptom

In lifting systems, such as those using a Linear Chain, the system may raise the load without any issues but fault when lowering it. In some cases, the lifting system also drops slightly before moving upward. This behavior can have several causes. Common possibilities include problems with the motor control, incorrect variable frequency drive (VFD) settings, or an issue with the braking resistor.

2. Troubleshooting procedure

2.1 Check motor size and motor data

First, verify that the installed motor is suitable for the application and the drive configuration.

Check the following:

1. What motor power is installed?
2. Is the motor sized correctly for the required load?
3. Is the motor connected properly to the VFD?

2.2 Verify the VFD settings

If the system operates in only one direction and faults while lowering the load, the next step is to inspect the VFD parameter settings.

Check the following:

1. Are the motor data entered correctly?
2. Are the rotation direction settings configured properly?
3. Are the acceleration and deceleration times set appropriately?
4. Are the current and torque limits configured correctly?
5. Are the load braking settings correct?

Incorrect parameter settings can prevent the lifting motion from being controlled properly. As a result, the VFD may detect an unacceptable operating condition and shut the system down with a fault.eration.

2.3 Inspect the braking resistor

When lowering a load, regenerative energy may be fed back into the drive system. Therefore, the braking resistor should also be inspected.

Check the following:

1. Is a suitable braking resistor installed?
2. Is the braking resistor connected correctly?
3. Is the braking resistor operating properly?

If the braking resistor is not connected correctly or is configured improperly, the VFD may detect an overvoltage condition during lowering and shut down the system.

3. Practical tips

If a system using a Linear Chain operates in only one direction, faults while lowering, and briefly drops before moving upward, the troubleshooting process should be carried out systematically.

Pay particular attention to the following:

1. Verify the motor size and motor data.
2. Check the VFD parameters.
3. Confirm the rotation direction and motion settings.
4. Inspect the braking resistor and its wiring.

Not every problem that occurs in a Linear Chain or Screw Jack system is caused by the mechanical components. Incorrect motor or VFD settings are often responsible for faults that affect the lifting motion.