AdvancedMedium risk

VSD powered and fault-free but won't accept the run command

The drive is powered, shows no fault, and the display looks normal — but it ignores the run command and the motor never turns. Often a 'not ready' / 'STO' / enable status, not a trip.

Start fault-finding Log readingsEnter Job Mode

Safety first

Safe Torque Off (STO) and enable inputs are safety functions — they are there to stop the motor running. Never strap or defeat an STO/enable to 'make it go'. Work to the drive manual and the machine safety drawings.

Isolate, lock out / tag out, and prove dead before working unless a live test is specifically required, authorised, and carried out under proper supervision. Always follow local regulations, your site procedures, and the equipment manufacturer's documentation.

Apprentice mode

Full walk-through — the why, what readings mean, mistakes & safety.

Likely causes

Ranked from most to least likely.

  1. 1

    Safe Torque Off / enable input not satisfied

    Most likely

    Most drives won't run unless the STO/enable terminals are made by the safety circuit (E-stop, guard, safety relay). If that circuit is open, the drive stays 'not ready' with no fault.

  2. 2

    Run command not reaching the drive / wrong control source

    #2

    The drive may be set to take its run command from a different source (terminals vs keypad vs network) than the one being used, so the command is ignored.

  3. 3

    Missing run permissive / interlock

    #3

    A process interlock (level, pressure, door, upstream ready signal) that must be made before run is missing, holding the drive off by design.

  4. 4

    Drive in local/keypad mode or disabled

    Least likely

    The drive left in local/hand or with a disable parameter set won't respond to the remote run command.

Reports are saved on this device to reflect what you actually find.

Testing sequence

Work through one test at a time. Expected reading and what each result means.

On the tools? Job Mode shows one test at a time with thumb-sized buttons — your place and readings carry straight over.

Enter Job Mode
Test 1 of 3
1

Read the drive's status/ready indication and check whether STO/enable shows satisfied or open.

Expected reading

Drive shows ready with STO/enable made.

If it passes

Safety enable is made — look at the run command source and permissives.

If it fails

STO/enable not satisfied — trace the safety circuit (E-stop, guard, safety relay). Do NOT bypass it.

Often leads toVSD powered up but won't start the motorE-stop circuit won't reset / machine won't start
Mark this test
View all expected readings at once
1. Read the drive's status/ready indication and check whether STO/enable shows satisfied or open.
Drive shows ready with STO/enable made.
2. Confirm the drive's commanded control source (terminal/keypad/network) matches how the run command is being given.
Control source matches the command method being used.
3. Check any run permissives/interlocks (level, pressure, door, upstream ready) are made.
All required permissives present.

Fault-finding flowchart

The same logic as a decision tree.

  1. 1
    start

    VSD won't accept run, no fault

    → step 2
  2. 2
    decision

    Is STO/enable satisfied (drive ready)?

    Yes→ step 3No→ step 4
  3. 3
    decision

    Does the control source match how run is commanded?

    Yes→ step 5No→ step 6
  4. 4
    result

    Safety enable open — trace the safety circuit (do not bypass).

  5. 5
    decision

    Are all run permissives/interlocks made?

    Yes→ step 7No→ step 8
  6. 6
    result

    Wrong control source — set terminal/keypad/network to match.

  7. 7
    result

    Recheck local/remote mode and any disable parameter.

  8. 8
    result

    Missing permissive/interlock — satisfy the real condition, don't defeat it.

Common mistakes apprentices make

  • Strapping out an STO/enable or interlock to force a run — defeating a safety function.
  • Looking only for a fault code when the issue is a 'not ready' status.
  • Sending a keypad command while the drive is set to terminal/network control.
  • Missing a process permissive that must be made first.

When to stop & escalate

Any STO/enable/safety-circuit issue is a safety matter — escalate and resolve the safety circuit properly rather than bypassing it. If a permissive is missing due to an upstream process fault, hand off to the relevant system owner.

If you're past your competence, authorisation, or the safe limits of the job — stop and hand it on. There's no fault worth getting hurt over.

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