Masterdrive CUVC Parameter Recovery After P970 Factory Reset

Problem Summary

A Siemens Masterdrive CUVC vector-control inverter on an Atlas Copco air compressor loses its application-specific configuration and fieldbus communication with the Elektronikon 5 graphic front panel immediately after a factory reset triggered by P970. The compressor typically runs in regulation while the Elektronikon reports "no communication with drive," "inverter alarm," or "drive not ready" depending on firmware revision.

This article documents the parameter recovery procedure used in the field, including DriveMonitor upload, manual parameter entry, and Atlas Copco parameter-set retrieval. The same procedure applies to Masterdrive VC (6SE70) and Masterdrive MC (6SE70) variants used in GA, GX, and Z-series Atlas Copco compressors.

Root Cause: P970 Factory Reset Behavior

The factory-setting parameter P970 in Masterdrive CUVC firmware has three functional values:

When P970 is executed, the CUVC control board reinitializes the following critical data areas:

• All P001 through P999 writable parameters in all three parameter sets (0, 1, 2)
• Setpoint source selection (P443, P554, P555)
• Fieldbus gateway settings (USS: P780-P786; Profibus: CBP2 module parameters P700-P746)
• Motor data block (P100-P110, P340-P352)
• Free-function blocks and BICO interconnections

After the reset, the drive reverts to the default control wiring: analog input 1 (terminal X101.5/6) as main setpoint, fixed setpoint 1, and CB/TPM communication as control source. If the Elektronikon 5 was previously using Profibus (CBP2) or USS over a CBP/COM module, that mapping is cleared and the drive no longer responds to controller requests.

Pre-Reset Recovery Assessment

Before requesting a new parameter file or starting manual entry, verify the following on the PMU (Parameterization Unit) on the front of the drive:

1. Press the P key on the PMU to enter parameter mode.
2. Navigate to r071 (Mains voltage) and confirm the CUVC detects the correct supply (400 V / 480 V / 690 V depending on compressor build). This confirms the control board is healthy.
3. Read r070 (current firmware version) and r069 (build number). The CUVC firmware version affects which DriveMonitor backup file is compatible. Common Atlas Copco builds use firmware V2.6, V2.7, or V3.2.
4. Check the fault memory r947 and r949 to identify whether the original reset was triggered by a fault or by deliberate service action.
5. Inspect parameter index selection: P971 = currently selected parameter set, P972 = copy source, P973 = copy destination. After a reset, all three should display factory values.

If the OEM parameter block was previously written to a memory card (if the CUVC has the optional PCMCIA slot on the 6SE70 board), the parameter backup can be recovered directly from the memory card without contacting Atlas Copco. The CUVC reads Sxx*00.000 files from the memory card in directory \.

Parameter Recovery Method Selection

Three recovery paths are available. Selection depends on what you have in hand.

Method 1: DriveMonitor Parameter Upload

DriveMonitor is the original Siemens commissioning tool for Masterdrive (6SE70/6SE71). It communicates over the front serial port (X300, RS232, 9.6 kbit/s default) or via PROFIBUS-DP using the CBP2 module. DriveMonitor v6.5 SP1 supports Masterdrive CUVC firmware V2.6, V2.7, V3.0, V3.1, V3.2, and V3.3 and is available on the Siemens Industry Online Support portal.

Hardware Connection

1. Use a Siemens 6SE7090-0XX84-4FS0 / 6SX7005-0AB00 serial cable (or a generic 9-pin RS232 straight-through, no handshake required at 9.6 kbit/s for the front port).
2. Plug the cable into the X300 serial port on the front of the CUVC, behind the PMU cover.
3. Connect to the PC COM port or USB-to-RS232 adapter (FTDI-based units are recommended; check for direct drive on the CFT signal).
4. Set the DIP switches on the CUVC if required: most Masterdrive CUVC boards default to 9.6 kbit/s, even parity, 8 data bits, 1 stop bit (9,6E/8/1).

DriveMonitor Configuration

1. Launch DriveMonitor version 5.x or 6.x.
2. Set the connection: Online → Set PC-PG Interface → COM Port → 9600 → Even → 1 stop bit.
3. Click "Connect" (the F5 key). The CUVC replies with firmware version and build. If it fails, verify the bus terminator on the CUVC is OFF (only one device at the end of the bus is terminated) and that the cable is wired straight through (2-2, 3-3, 5-5).
4. Read the live parameters: Drive → Upload Parameter Set to PC (RAM upload). This loads the current (post-reset) configuration, which is useful for diff against the backup file.
5. Open the backup file (.dnx for parameter set 1, or .pnx for all three sets) with File → Open.
6. Download the backup to the drive: Drive → Download Parameter Set to Drive. Choose parameter set 1, 2, or "all sets."
7. Cycle the CUVC power (24 V control supply or main power) so the new parameter set is stored in the EEPROM and read on power-up.

Method 2: Manual Parameter Entry via PMU

If no electronic backup exists, the parameter values must be entered one by one through the PMU. The PMU uses a 4-key pad: P (parameter), plus, minus, and a 7-segment display for parameter number and value.

1. Press P. Display shows P000 or last edited parameter.
2. Use up/down to navigate to the target parameter (e.g., P100 = motor type).
3. Press P again to read the value. Press P a third time to edit; the value blinks.
4. Use up/down to change. Press P to confirm and step to the next parameter in numerical order.
5. For multi-set parameters, repeat for set 2 and set 3 by selecting P971 = 2 or P971 = 3 before navigating.

Critical Parameter Group Table

The following parameters must be re-entered from the Atlas Copco design sheet. Values shown are representative for a GA75 VSD compressor with a 75 kW Masterdrive MC; consult the Atlas Copco machine-specific data plate and parameter sheet for exact values. For full parameter definitions, see the Siemens SIMOVERT MASTERDRIVES Vector Control CUVC parameter list (DA65.10) on the Siemens Industry Online Support portal.

The full CUVC parameter list runs from P000 to P999; in production firmware approximately 720 parameters are active. A complete Atlas Copco commissioning sheet typically covers 80 to 130 parameters for a standard VSD compressor.

Method 3: Atlas Copco Parameter File Request

When neither a DriveMonitor backup nor a commissioning sheet is in hand, contact Atlas Copco Service with the following information to obtain the correct parameter file:

1. Compressor serial number (e.g., GA75VSD serial 6-digit code on the data plate).
2. Masterdrive CUVC type (e.g., 6SE7090-0XX85-1FB0 or 6SE7090-0XX85-1BD0 - the suffix indicates rated current and voltage).
3. Elektronikon controller type (Mark IV, Mark V, Elektronikon 5, Elektronikon 6).
4. Firmware versions: r069 (CUVC), r470.001 (CBP2 if present), and the Elektronikon 5 software version from its display (Service → About).
5. Year of manufacture and application (oil-injected screw, oil-free tooth, centrifugal).

Atlas Copco issues the parameter file as a DriveMonitor archive (.dnx or .pnx) and the corresponding parameter list (PDF). Service access usually requires the site to be on a SmartLink service contract or the customer to confirm warranty status. The file is downloaded to the CUVC with the same DriveMonitor procedure as Method 1.

Masterdrive CUVC Communication Architecture

The communication path between the Elektronikon 5 controller and the Masterdrive varies by compressor generation:

The CUVC exposes three control sources selectable per P554/P555:

• Terminals (digital inputs X101.1-X101.8): hard-wired start/stop, fault reset
• USS on the front serial port X300 or the COM/CB module: serial protocol, addresses 0-30
• Fieldbus (Profibus, CANopen, DeviceNet) via the optional CBP2 board plugged into the CUVC backplane

When P970 resets the drive, all three sources are re-initialized. The most common cause of the "Elektronikon 5 reports no communication" symptom is that P554 = 41 (fieldbus) was overwritten to P554 = 20 (analog input 1) or P554 = 0 (terminals). The Elektronikon continues to send PROFIBUS telegrams, but the CUVC no longer interprets the control word bits.

Fieldbus Parameter Restoration

Profibus (CBP2) Restoration

USS (X300 Serial) Restoration

Verification Procedure

After the parameter file is loaded, run the following verification sequence before releasing the compressor:

1. Power cycle. Disconnect the CUVC 24 V control supply (X9 connector on the backplane) for 30 seconds, then restore. Confirm r069 (firmware) and r070 (mains detection) are present and stable.
2. Motor identification. Run P115 = 1 (motor identification routine). The drive pulses the motor without rotation and measures stator resistance and leakage reactance. This step is mandatory after a P970 reset; otherwise the controller uses estimated motor values and vector control is unstable. The routine takes 30-60 seconds; F042 signals completion if the routine aborts. If F042 appears, check that the motor is correctly wired (no missing phase) and that P100-P110 match the motor nameplate.
3. Fieldbus handshake. From the Elektronikon 5 service menu (Service → Inverter → Communication), request a Profibus/USS read. The CUVC should return a status word 1 = 0x6AF (Ready, No Fault, Run Enable, Inverter Enabled). If the status is 0x000, the BICO mapping is still wrong.
4. No-load jog. With the compressor unloaded and inlet valve open, command 5 Hz from the Elektronikon. Observe motor current (r019) and DC bus voltage (r022). Current should be 30-50% of motor rated. DC bus should stabilize at 1.35 x mains V (e.g., 540 V DC on 400 V AC mains).
5. Load step test. Open the service air valve to draw 50% of rated flow. Confirm that the Elektronikon 5 ramp tracks the pressure setpoint within 0.2 bar and that the drive does not trigger F011 (overcurrent) or F029 (inverter overload). On a cold motor, I²t can take 10-20 minutes to settle.
6. Fault log clear. If the original reset was triggered by an Fxxx fault, clear the fault memory with P952 = 4 and acknowledge at the Elektronikon.

Common Recovery Errors and Resolutions

Preventive Measures

To avoid future P970 reset incidents, implement the following safeguards:

1. Password-protect parameter access. Set P050 = password on the CUVC. The default is 0 (unrestricted). With a password, a service engineer must intentionally reset to factory defaults via P970 = 1, reducing accidental resets.
2. Back up before any service. Add a DriveMonitor download step to every preventive-maintenance checklist. The five-minute upload is trivial compared to four hours of manual parameter recovery.
3. Document the parameter file location. Store the .pnx file in the same folder as the compressor's electrical drawing, ideally with the SmartLink service record if the compressor is networked to Atlas Copco.
4. Mark the PMU with a clear label: "RESET TO FACTORY = P970 = 1 - REQUIRES OEM PARAMETER FILE TO RECOVER." The PMU is on the front of every Masterdrive; most accidental resets are caused by technicians reading the parameter list and entering the wrong number.
5. Validate after any firmware update. If the CUVC firmware is updated by the field service, the OEM parameter block must be reloaded. Document the firmware version on the drive's data plate sticker.

Cross-Reference: Masterdrive CUVC to Siemens SIMOVERT Migration

Atlas Copco compressors older than 2010 often carry a Siemens Masterdrive 6SE70 (VC or MC) and increasingly have been replaced by SINAMICS G120/G150 or SINAMICS S120 in the field. The parameter mapping is not 1:1; the core motor data block (P100-P110, P340-P352) maps to the SINAMICS p0300-p0350 group, and the BICO interconnections in P443/P554/P555 map to SINAMICS p840-p854 (control words) and r2050 (PZD receive). Migration guides are published on the Siemens Industry Online Support portal under search term "6SE70 to SINAMICS migration."

For migration projects, the original Masterdrive .pnx parameter file is still useful as the design record; it should be archived even if the drive is replaced, because the compressor's mechanical performance is fully characterized by that parameter set.

FAQ