Err02 - PwnCNC

Err02

Over-current at acceleration

When the frequency inverter accelerates, output current exceeds over-current.

Check whether the motor is and its lines are short circuit, grounded or too long;
Check whether the input voltage is relatively low;
Delay the acceleration time;
Conduct parameter identification or improve low frequency torque compensation or adjust V/F Curve;
Check whether the load has mutation;
Check whether it is to select speed tracking or start after the motor stops stably;
Check whether the rated power of the motor or frequency inverter is large enough;

ERR02 – Over-Current During Acceleration

What this means

ERR02 occurs when the VFD detects too much current while the spindle is accelerating up to speed. This happens before the spindle reaches its commanded RPM, typically right at startup or just as cutting begins.

In simple terms, the spindle is being asked to spin up faster or under more load than the electrical system can safely support.

Most Common Causes (Real-World)

1. Acceleration time is too aggressive

This is the most common cause of ERR02.

If the spindle is commanded to reach full RPM too quickly, the inrush current during acceleration can exceed safe limits.

What we typically ship:

Acceleration time set to 6 seconds

Depending on tooling, material, and electrical conditions, some setups benefit from slowing this down.

2. Controller and VFD acceleration times do not match

This is especially important for controllers like Masso.

If:

You increase acceleration time in the VFD, but
Do not update the spindle acceleration time in the controller

the machine may begin moving into the material before the spindle is fully up to speed, causing a sudden load spike that trips ERR02.

Both values must match.

3. Sudden load during startup

Examples:

Straight plunges into material
No ramp or lead-in
Tool already engaged when the spindle starts

Any abrupt load during acceleration can cause current to spike.

4. Low or unstable input voltage

During acceleration, the spindle draws more power. If the input voltage dips:

The VFD compensates by pulling more current
This can trigger an over-current fault

This can happen even on dedicated circuits due to:

Long wiring runs
Loose outlets or terminals
Other large motors starting on the same electrical service

5. Motor cable or grounding issues

Less common, but worth checking:

Loose motor connections
Excessively long motor cables
Ground faults or damaged insulation

What to Do First (Recommended Order)

Step 1: Increase acceleration time

This resolves the vast majority of ERR02 cases.

Increase the VFD acceleration time
Parameter: P0.0.11
Try increasing from 6 seconds to 8 seconds or higher

⚠️ Important for Masso users:
Also update the Spindle Acceleration Time in Masso’s spindle setup to match the VFD value exactly.

Step 2: Reduce startup load

Use ramped tool entries instead of straight plunges
Avoid starting the spindle while already engaged in material
Reduce plunge rate if needed

Step 3: Check electrical supply

Plug the VFD directly into the wall outlet
Avoid extension cords or power strips
Verify input terminals at the VFD are tight

Step 4: Inspect motor wiring

Confirm motor cable connections are secure
Check for damage or pinched cables
Verify proper grounding

Important Notes

ERR02 is a protective fault, not a failure
It does not indicate a damaged spindle
Repeated ERR02 events are a sign the acceleration profile or startup load needs adjustment

Summary

ERR02 means the spindle is being overloaded while accelerating.

In almost all cases:

Increase acceleration time
Ensure controller and VFD acceleration settings match
Avoid sudden load at startup

If ERR02 persists after increasing acceleration time and reducing startup load, contact support with details about your controller, spindle RPM, tool type, and cutting strategy.