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SD700 Pulse Mode Quick Troubleshooting

This guide provides a quick troubleshooting procedure for the VEICHI SD700 servo drive when the motor does not run correctly in pulse position control mode.

1. Preliminary Check​

Before troubleshooting individual parameters, it is recommended to restore the drive parameters to the factory default settings if necessary.

This helps rule out problems caused by incorrect or conflicting parameter settings.

Note: After restoring factory settings, reconfigure all parameters required for the actual application before running the machine.

2. Check the Electronic Gear Ratio​

Make sure that the electronic gear ratio parameters are set correctly:

  • Pn204
  • Pn206

If the motor encoder resolution, such as 17-bit or 23-bit, is unknown, you can use the following simplified setting method:

Pn204 = 0
Pn206 = Number of command pulses required for one motor revolution

For example:

Pn204 = 0
Pn206 = 10000

This means that 10,000 input pulses command the motor to rotate one revolution.

3. Motor Does Not Run in Pulse Control Mode​

If the servo motor does not run in pulse control mode, check the following items in order.

Step 1 — Test JOG Operation​

Run the motor in JOG mode first.

Confirm that:

  • The motor can rotate normally.
  • The motor and encoder are functioning correctly.
  • There is no mechanical blockage.

If the motor cannot run in JOG mode, troubleshoot the motor, encoder, wiring, or mechanical system before checking the pulse command.

Step 2 — Confirm Servo Enable​

Make sure that the servo is enabled.

For testing, internal servo enable can be used:

Pn001 = 1

Confirm that the drive enters the Servo ON state.

Step 3 — Check Pulse Command Input​

Observe:

Un006 — Pulse Input Pulse Counting

Send pulse commands from the controller and check whether the value of Un006 changes.

  • If Un006 counts normally, the pulse command is reaching the servo drive.
  • If Un006 does not change, check the pulse wiring, signal type, controller output, and pulse input circuit.

Step 4 — Check Position Control Parameters​

Confirm the following settings:

Pn000 = 1

Position control mode.

Pn208 = 0

Position command is provided by an external pulse input.

Also confirm that:

Pn204 / Pn206

are set correctly for the required electronic gear ratio.

If the parameter configuration is uncertain, restoring the parameters to factory defaults can also be used as a troubleshooting method before reconfiguring the required settings.

4. Running Speed Is Incorrect​

If the motor runs but the actual speed is not as expected, observe:

Un104

and calculate the theoretical motor speed according to the pulse frequency and electronic gear setting.

For example:

Pn204 = 0
Pn206 = 5000
Un104 = 30000 Hz

When Pn204 = 0, Pn206 = 5000 means that 5,000 pulses correspond to one motor revolution.

The theoretical motor speed is:

30000 / 5000 × 60 = 360 r/min

Therefore:

Theoretical Speed = 360 r/min

If the calculated speed is correct but the actual motor speed is abnormal, continue checking the command source, mechanical load, speed limitation, and other related parameters.

5. Check for Motor Blocking​

If the servo is enabled and pulse commands are received but the motor still cannot rotate, check for mechanical blocking.

Typical causes include:

  • The motor holding brake has not been released.
  • The mechanical load is jammed.
  • The motor shaft cannot rotate freely.
  • The load is too heavy.

Observe:

Un002 — Torque Feedback

If the torque feedback becomes very high while the motor does not rotate, this may indicate that the motor is mechanically blocked or that the holding brake is still engaged.

Caution: Do not repeatedly command the motor to run when it is mechanically blocked or when the holding brake is engaged.

Quick Troubleshooting Flow​

Motor does not run
        │
        ▼
Can the motor run in JOG mode?
        │
   No ──┴── Yes
   │         │
Check motor,  Confirm Servo ON
encoder,      │
wiring and    ▼
mechanics   Does Un006 count?
              │
         No ──┴── Yes
         │         │
      Check pulse  Check Pn000 / Pn208
      wiring and   and Pn204 / Pn206
      controller         │
                         ▼
                   Motor runs?
                         │
                    No ──┴── Yes
                    │         │
                Check brake,  Check Un104
                load and      and calculate
                Un002 torque  theoretical speed

Parameter Reference​

Parameter / MonitorPurpose
Pn000Control mode selection
Pn001Servo enable setting
Pn204Electronic gear ratio related setting
Pn206Electronic gear ratio related setting
Pn208Position command source setting
Un002Torque feedback
Un006Pulse input pulse counting
Un104Pulse command frequency / related monitoring value used for speed verification

For most pulse control problems, use the following sequence:

JOG test → Servo ON → Check Un006 → Check Pn000/Pn208 → Check Pn204/Pn206 → Verify speed with Un104 → Check brake/load and Un002

This sequence helps separate motor or mechanical problems, servo enable problems, pulse input problems, and parameter configuration problems efficiently.