Fixing Simovert Masterdrive MC Setpoint Not Accepted

Problem Description

When commissioning a Siemens Simovert Masterdrive MC (also branded as Masterdrives MC in later generations) through the DriveMonitor commissioning tool, operators using the "Request Master Control" panel sometimes encounter a stuck state where the drive accepts the run (ON/OFF1) command but refuses to apply the commanded setpoint. The drive HMI simultaneously displays the characters "0" and "1" (interpreted as an alternating two-digit state indicator that toggles between two mutually incompatible drive states), and subsequent attempts typically escalate to alarm A034 "Setpoint/Actual value deviation".

The symptom set as it appears on a real machine is reproducible and consistent across firmware generations of the Masterdrive MC product family:

• DriveMonitor issues ON through Request Master Control → drive status word reports Operation Enabled.
• Setpoint slider or numeric input on the Request Master Control panel has no observable effect on motor shaft speed or torque output.
• The HMI alternates between two characters ("0" and "1") instead of a normal single-digit status code.
• After the configured deviation-monitoring window expires, the drive raises alarm A034.
• The motor shaft does not rotate even when the run command has been latched.

This is one of the more common start-up faults reported on Masterdrive MC units still in service. The cause is almost always a control-word or setpoint-source configuration that has not been aligned with the mode in which the operator is commanding the drive. The Masterdrive MC platform — a vector-controlled AC drive built around the SIMOVERT architecture — is highly configurable, and the same drive can be operated as a speed controller, torque controller, or position controller with very different parameter requirements.

How Request Master Control Works in DriveMonitor

DriveMonitor (also called SIMOVIS DriveMonitor in older Siemens documentation) is the Windows-based commissioning tool that talks to a Masterdrive MC unit over the serial RS232/USS service interface on the front of the control electronics, or over PROFIBUS through a CBP2 communication board. When the operator invokes the "Request Master Control" panel, DriveMonitor asks the drive to temporarily grant the PC commissioning software master control authority over the drive's control word and setpoint paths. This is invaluable for step-by-step commissioning because it removes the dependency on hardwired terminal states while the engineer is troubleshooting.

For the drive to actually apply a setpoint from this path, the following must be true simultaneously:

1. The control-word source selector (P590) must be in a state that allows the software master path to be active, or the operator's DriveMonitor version must be granted master through its own override mechanism.
2. All control-word enable bits that gate the setpoint (typically ON/OFF1, Enable, Setpoint Enable, Ramp Enable, and similar) must be HIGH.
3. The operating mode selected in the drive (speed control vs. torque control vs. position control) must match what the operator is commanding. A speed setpoint into a position-controlled drive will fail because the position controller interprets the input as a position increment, never closes the loop, and the drive generates A034.
4. The torque and current limits must be non-zero.
5. The motor and feedback chain must be intact so that actual speed tracks commanded setpoint within the deviation window.

Any one of these pre-conditions failing will manifest as the exact "run accepted, setpoint ignored" symptom described in the original field report.

Root Cause Mapping

The Masterdrive MC distinguishes between a run-enable path and a setpoint-enable path inside its control word. ON/OFF1 typically enables the drive state machine; OFF2 and OFF3 are stop paths; the setpoint is gated separately through bits that must also be HIGH for the setpoint to reach the ramp function generator. This is why the operator sees "run accepted" — the state machine is enabled — but the setpoint is ignored — the setpoint gating bits are not at the level the drive expects. The alternating 0/1 HMI display indicates that the drive state machine is toggling between two mutually exclusive operating modes or has latched a warning alongside the operational state.

Pre-conditions Checklist

Before invoking Request Master Control, the following drive-side conditions must hold. The field report indicates these were enabled in the control panel, but each must be re-verified after any parameter download because some Masterdrive parameter changes do not become active until the drive is stopped, restarted, or re-energized.

Parameter Diagnostic Procedure

Work through the following parameters in order. Save the active parameter set to a backup file before making changes — DriveMonitor → Parameter → Upload (Drive → PC) — so the original commissioning can be restored if required.

Step 1 — P590 Master Control Source

P590 selects the master control source. On the Masterdrive MC platform, the standard terminal/process-data path is associated with the factory-default value of P590 = 0. When the operator invokes Request Master Control from DriveMonitor, the tool attempts to inject its own control word into the drive state machine; this works only when P590 is configured to a value that allows the software master to take precedence, or when the firmware permits the Request Master Control override at the application level.

Action: verify P590 = 0 if the installation is a standard terminal-controlled drive. If the drive is configured for a fieldbus master (Profibus via CBP2, USS, or PROFINET), DriveMonitor will not have authority and the operator must either change P590 to the appropriate terminal/source value for the duration of the test or use a hardware master on the fieldbus side.

Step 2 — P556, P557, P559, P560 — Binary Input Bits

These parameters map the physical binary input terminals (and, on some configurations, the control word bits delivered by an option board) to the individual control word bits used for setpoint gating. The field-tested recommendation specifies that Index 1 of each parameter must show a HIGH level. The Index 1 sub-parameter, in the Masterdrive MC convention, corresponds to the second selectable signal source for that bit — typically used when the drive is operating with a serial or bus master instead of a hardwired terminal master.

Procedure:

1. In DriveMonitor, open the parameter list (Parameter → Parameter List, or the online parameter tree).
2. Navigate to P556, P557, P559, P560.
3. For each parameter, expand Index 1.
4. Read the bit assignment — confirm that the desired control functions (typically ON/OFF1, Enable Operation, Setpoint Enable, Ramp Enable) are mapped to a HIGH signal source.
5. If a bit is mapped to a LOW source or to an unassigned source, force HIGH through DriveMonitor or correct the source mapping.

The exact terminal-to-bit correspondence depends on the option board installed (CBP2 Profibus, CBC CAN, SLB, etc.) and on the firmware version. Always refer to the parameter list specific to the firmware revision in service.

Step 3 — P210 and P772 — Position Control Disabling

For pure speed-control operation, P210 (position controller enable) and P772 (technology function selection for positioning) must both be set to 0. The Masterdrive MC supports a position controller as an optional technology function layered on top of the speed controller; when enabled, the drive interprets the input setpoint as a position increment (typically in encoder pulses) and closes the loop against an internal position reference.

If the operator is sliding a continuous speed setpoint in the Request Master Control panel while P210 or P772 is non-zero, the drive is interpreting the continuous value as a position command that never converges. The position controller cannot close the loop on a continuously moving setpoint, so the drive sees a setpoint/actual deviation and raises A034.

Action: set P210 = 0 and P772 = 0. If the application genuinely requires position control, the operator must use the appropriate positioning panel in DriveMonitor, not the Request Master Control speed slider.

Step 4 — Torque and Current Limits

If P170–P173 (torque limits, depends on firmware variant) or P128–P129 (current limits) are zero or have been corrupted by a parameter download from a different motor rating, the drive will accept the run command and the setpoint but cannot develop any torque. The motor will not move. DriveMonitor will display no alarm other than the eventual A034.

Action: re-enter torque and current limits from the motor nameplate. If the motor identification routine (P115 or its firmware-variant equivalent) has not been run since the last parameter reset, run it now — the identification routine calculates the correct torque and current limits for the connected motor.

Step 5 — Motor and Feedback Integrity

With the drive fully de-energized and the DC bus confirmed discharged, perform the following checks:

• Continuity across each motor phase at the drive output terminals.
• Insulation resistance (megger) between phases and between each phase and ground — typically minimum 1 MΩ per kV of supply voltage.
• Encoder cable shield continuity, pinout against the encoder manual, supply voltage present at the encoder end.
• Manual rotation test: with the drive still de-energized, turn the motor shaft by hand and observe the actual speed feedback (r000 or r021) live in DriveMonitor. If actual speed remains zero, the feedback chain is open and the drive will never be able to close its speed loop — A034 is inevitable.

Alarm A034 — Setpoint/Actual Value Deviation

Alarm A034 fires when the absolute difference between commanded setpoint and measured actual value exceeds the configured monitoring threshold for longer than the configured monitoring window. On the Masterdrive MC the threshold and window live in the parameter range around P530–P590 depending on firmware, typically expressed as a percentage of rated speed and a number of milliseconds.

Step-by-Step Recovery Procedure

Apply the following ordered procedure. After each step, stop and observe whether the original symptom has cleared before moving to the next.

1. Place drive in safe state — Remove ON command from Request Master Control; verify Ready state in DriveMonitor. Open the upstream main contactor to remove AC supply. Wait for the DC bus discharge time stated on the unit label.
2. Upload parameter backup — DriveMonitor → Upload (Drive → PC). Save with a timestamp and label indicating the motor nameplate rating.
3. Set P590 = 0 if the drive is configured for terminal/source control. Download to drive.
4. Inspect P556, P557, P559, P560 Index 1. If any required bit shows LOW where HIGH is expected, force HIGH through DriveMonitor or correct the source mapping. Download.
5. Set P210 = 0 and P772 = 0 for speed control operation. Download.
6. Re-enter torque and current limits from the motor nameplate. Download.
7. Verify motor and feedback wiring with the drive de-energized. Confirm encoder pulses by rotating the shaft and observing r000 live in DriveMonitor.
8. Run motor identification if available on the firmware version. This re-runs the motor model and clears stale identification data.
9. Re-attempt Request Master Control. Confirm setpoint is applied and motor responds proportionally.
10. Record final parameter set. Save with the commissioning date and engineer initials.

Factory Reset and Re-Commissioning

If targeted parameter diagnostics do not restore normal operation, factory reset followed by fresh commissioning is the most reliable recovery. The Masterdrive MC supports parameter reset to factory defaults through parameter P970 on most firmware versions; the exact procedure depends on the installed firmware revision and the operator should consult the specific parameter list.

1. Upload existing parameters to PC and archive.
2. Set P970 to the appropriate factory-reset value per the firmware documentation for the unit.
3. Execute the reset; wait for the drive to restart.
4. Re-enter motor nameplate data into P110–P130.
5. Run automatic motor identification (P115 or firmware-equivalent).
6. Reconfigure P590, P556–P560, P210, P772 per the application.
7. Test with Request Master Control.
8. Save the new parameter set as the commissioned baseline.

Masterdrive MC Communication Setup

DriveMonitor communicates with the Masterdrive MC over the front RS232 service port using the USS protocol at a default baud rate. If communication fails or hangs partway through parameter uploads, the operator may see partial parameter sets and a drive that responds to commands without honoring setpoints — a related but distinct symptom. Verify the following before concluding that the parameter configuration is at fault:

• USS address matches between DriveMonitor and the drive (parameter for USS address on the Masterdrive MC is typically P780 in the communication parameter range, depending on firmware).
• Baud rate matches — typical default 19200 or 9600 baud.
• RS232 cable is the Siemens-specific service cable; a generic null-modem cable may not work because of the handshaking wiring.
• If communicating over a CBP2 PROFIBUS option board, PPO type and PROFIBUS address must match what DriveMonitor is configured to expect.

Control Word and Status Word Reference

Although the exact bit assignment depends on the Masterdrive MC firmware and the option board configuration, the conceptual structure of the control word is stable across the product family. The following table summarizes the bits most often involved in the Request Master Control symptom.

If the operator sees "run accepted, setpoint ignored", bits 0 and 3 are HIGH but at least one of bits 4, 5, or 6 is LOW. These bits are typically the ones mapped in P556, P557, P559, P560.

Verification Checklist

After applying the corrective action, validate the fix end-to-end:

• Drive accepts ON command from Request Master Control and transitions to Operation Enabled.
• Setpoint input from Request Master Control produces proportional motor speed within the configured ramp.
• Actual speed reading (r000) tracks commanded setpoint.
• No A034 alarm under steady-state operation at any setpoint within the operating range.
• Direction reversal (negative setpoint) works without alarm, provided P571/P572 enable negative direction.
• HMI no longer displays alternating 0/1; normal single-digit status code is shown.
• Stable operation across at least one full acceleration-deceleration cycle.
• Stable operation across a step load change within the torque limit envelope.

Common Commissioning Pitfalls

Operators working on Masterdrive MC units frequently encounter the following pitfalls, several of which can mimic the Request Master Control fault:

• Firmware version mismatch: Parameter indices and defaults differ between Masterdrive MC firmware revisions. Always note the installed firmware version before parameter manipulation and consult the parameter list specific to that version.
• Option board swap: Replacing a CBP2 (PROFIBUS) with a CBC (CAN) or vice versa changes the meaning of P590 and the binary-input mapping in P556–P560. A parameter set from one configuration will not apply cleanly to another.
• Motor data not re-entered after factory reset: A freshly reset drive will not develop proper torque until P110–P130 (motor nameplate) are populated and P115 (motor identification) is run.
• Encoder simulation vs. actual encoder: Some applications use the encoder simulation output of one drive as the speed reference for another. Ensure the drive under commissioning is configured for the actual feedback source present at its terminals.
• Fieldbus master still broadcasting: When switching to Request Master Control for service, the upstream PROFIBUS or USS master may still be writing control words to the drive, which can override the DriveMonitor master. Disconnect the bus master or set the master to a passive state during PC-based commissioning.

Escalation Path

If the diagnostic procedure above does not restore normal Request Master Control operation, escalate through Siemens Industry Online Support. A complete parameter set (Upload from Drive) and a clear description of the symptom should be provided to the support engineer. The original Siemens support workflow for Masterdrive MC legacy units is reachable through the SIOS portal at support.industry.siemens.com.

Frequently Asked Questions