Replacing Danfoss VLT with Yaskawa A1000 on S7-400 Profibus

Overview

When an installed Profibus-DP drive is no longer available on the local market and a direct spare is unavailable, the engineer is forced into a heterogeneous drive migration. This article documents the field procedure for replacing a legacy Danfoss VLT series drive with a Yaskawa A1000 general-purpose drive equipped with the SI-P3 Profibus-DP option card, while the supervisory PLC is a Siemens SIMATIC S7-400 with a Profibus-DP master (CPU 400-2DP, e.g. 6ES7414-3EM07-0AB0 or 6ES7416-3ER05-0AB0 family).

Key technical risk: parameter channel (PKW) layout, PPO type selection, and consistent-data access (SFC14/SFC15) all differ between the two vendors. A simple "change the slave GSD" does not work without re-mapping the I/O addresses in the STEP 7 program. The procedure below walks through identification of the old addresses, installation of the new GSD, and rebuilding the drive Function Block (FB).

Drive Profile Comparison

Parameter	Danfoss VLT (legacy)	Yaskawa A1000
Drive family	VLT AutomationDrive (FC 301/302), VLT HVAC (FC 102), or Micro (FC 051) — verify nameplate	CIMR-AU (standard), CIMR-AU4A (400 V class)
Profibus option	MCA 101 Profibus-DP V1 (or integrated on -P variants)	SI-P3 Profibus-DP option card (inserted into CN5)
GSD file name (typical)	DANFOSS0.GSD or DANNFP04.GSD (VLT 3008 quick state)	YA0CI__.GSD (Yaskawa A1000 SI-P3)
PPO types supported	PPO1, PPO2, PPO5 (VLT default 8PD + 8PC control word + speed ref/status + main actual)	PPO type 1 (8 PZD), Type 2 (2 PZD + PKW), Type 5 (no PZD, PKW only); default PPO Type 2
Default PZD length	4 words input / 4 words output (configurable 0–16)	2 input + 2 output PZD minimum, up to 8/8
Control word source	CTW (16-bit), profile DS8.1 or FC profile	Yaskawa MEMOBUS-based with Drive Control Word b15:0 mapped to drive terminals/internal registers
Speed reference	Parameter 3-02 / 3-13 (reference scaling)	Parameter b1-01 (drive reference source selection)
Default node address	1 (changed via parameter 9-18 / 9-22)	0 (changed via parameter F6-30 on SI-P3)

Prerequisites

1. STEP 7 (Classic) V5.5 SPx or SIMATIC Manager with the installed GSD for the new A1000. Import via Options → Install GSD File, then restart HW Config.
2. Yaskawa A1000 SI-P3 GSD file: YA0CI__.GSD, plus the accompanying bitmap YA0CI__.bmp. Download from Yaskawa's official product page; type the option card catalog code SI-P3 into the search box on the Yaskawa Drives product portal.
3. The original STEP 7 project, archived as a .zip S7 backup from the S7-400 CPU. "I have the program uploaded from the CPU" satisfies this — confirm the project opens offline without password prompts and that the hardware configuration (HW Config) still matches the physical rack layout.
4. Access to the existing Danfoss VLT drive or at minimum the typed nameplate data (drive family, FC series, PPO configuration, DP slave address). If the drive is fully removed from the network, read the address from the master project under the DP slave's Properties → Assigning Parameters.
5. USB-to-Mini-B or RJ-45 cable for the A1000 keypad port (DriveWizard) to parameterize F6-30 (node address), F6-01 (comm loss detection), and b1-01 (reference source).
6. Familiarity with STEP 7 FBs and instance DBs, since the new drive FBs will be wired into existing structure.

Step 1: Identify the Original Danfoss Drive Addresses in the STEP 7 Program

Open the uploaded project offline in SIMATIC Manager. The replacement strategy lives or dies by finding the existing peripheral I/O ranges used by the Danfoss node.

Method A — HW Config: Open the S7-400 station, navigate to the Profibus-DP master system, find the slave with the Danfoss GSD identifier (commonly DANFOSS DRIVE FC-SERIES or similar). Double-click the slave and click "Assigning Parameters" or "Configuration". The right-hand pane shows Input address and Output address offsets for each configured PPO slot. For a default 4 PZD / 4 PZD arrangement the offset occupies 8 bytes input and 8 bytes output (e.g., PIW 512 .. PIW 518 and PQW 512 .. PQW 518).

Method B — Cross-reference in OB1/ST source: Use Edit → Cross-references or Ctrl+Alt+F in the program editor. Search for any symbolic or absolute I/O addresses that fall in the area the Danfoss slave occupied. Common patterns:

• L PIW 512 / T PQ W 512 (cyclic PIO — works only on non-consistent PZD)
• CALL SFC 14 / CALL SFC 15 with RECORD pointing to a data block (consistent reading, typical for PKW)
• Symbolic names set in the Symbols table, e.g., "VLT_CTRL", "VLT_RD", "VLT_WR"

If SFC14 DPRD_DAT and SFC15 DPWR_DAT are present in the program (search the FBs for them — "is there any SFC14 Read DP or SFC15 in your program?"), they confirm the exchange is consistent (entire PPO or PZD read/written atomically). This is the A1000 SI-P3 default when using PKW access. Reference: the Siemens "Consistent Data" primer, attachment 28991143_Consistent_Data_e.pdf, details why SFC14/15 are mandatory for payloads larger than 4 bytes or for any data that must arrive coherently (e.g., a 16-bit control word + 16-bit status word + parameter channel).

Step 2: Remove the Danfoss Drive and Install the Yaskawa A1000 GSD

1. In HW Config, right-click the Danfoss DP slave and Disconnect Master-Slave. Delete the slave from the master system once you have recorded its address space.
2. Re-import the Yaskawa GSD: Options → Install GSD File → Browse. Restart HW Config when prompted so the catalog tree refreshes.
3. Drag the "YASKAWA A1000 SI-P3" device from the catalog onto the same Profibus subnet at the same station address (typically 3 or 4). The node address set on the SI-P3 with parameter F6-30 must match.
4. Configure the slot: select the PPO module. For an A1000 SI-P3, default PPO Type 2 (2 output PZD + 4 PKW + 2 input PZD, 8/8 words) is recommended when status, control, and parameter access are all needed by the application. For pure closed-loop speed control with no parameter layering, PPO Type 5 (8 PZD) can be simpler.

Step 3: Build the New Yaskawa Drive FB

Author a fresh Function Block (FB100+) for the A1000 that:

1. Calls SFC14 "DPRD_DAT" to read the configured PPO into an Input DB. Example call interface for an A1000 at PE address 512 (16 bytes input area):

```text CALL SFC 14 // Read consistent DP data LADDR := W#16#200 // Input base address (decimal 512) RET_VAL:= #retVal // Returns a 16-byte process image RECORD := P#DB99.DBX 0.0 BYTE 16 // Target area in input DB NOP 0 ```

2. Calls SFC15 "DPWR_DAT" to write the output PPO from an Output DB:

```text CALL SFC 15 // Write consistent DP data LADDR := W#16#200 // Output base address RECORD := P#DB98.DBX 0.0 BYTE 16 // Source area in output DB RET_VAL:= #retVal NOP 0 ```

3. Decodes the Drive Control Word (Word 0 of the output PZD) into Yaskawa commands (e.g., drive run forward = bit 0, drive reverse = bit 1, fault reset = bit 14 in the A1000 control word convention) and assembles it byte-by-byte into #out_db.PZD1.
4. Scales the speed reference (Word 1 of the output PZD) from engineering units (0..100% or RPM) into the A1000 reference units, then writes to #out_db.PZD2.
5. Decodes Drive Status Word (Word 0 of input PZD) and Actual Frequency/Hz (Word 1 of input PZD) to publish for the rest of the program.
6. If PKW is in use, parameterize drive parameters through the PKW channel: build a request (parameter number, index, sub-index) and parse the reply.

Keep all drive parameters in one Input DB DB99 and one Output DB DB98, both with the comment field listing parameter names and units. This keeps the cross-reference tight.

Step 4: Adjust Symbolic Addresses and Remove the Old Logic

Strip the Danfoss FB and its instance DB from the online program. Update the caller (typically OB1 or an instance-DB-bound cyclic FB) to call FB100 (Yaskawa A1000) instead of the old Danfoss FB. Re-wire all symbolic references of the old drive (e.g., VLT_CTRL.CMD, VLT_CTRL.SETP, VLT_STATUS.ACT_FREQ) to the new FB's outputs. Watch out for these legacy artifacts:

• Bit definitions in the status word that the old logic relied upon (e.g., "drive in ramp", "torque limit reached") typically map to different bits on Yaskawa. Confirm each bit by reading the A1000 "Programming Mode" reference manual, sections "Drive Status Word" and "Drive Control Word".
• Reaction to communication loss: Danfoss uses parameter 8-04 (Control Word Bit 9) or 9-60 (Profibus Watchdog) for fault behavior. Yaskawa uses F6-01 = 1 (EStop), F6-02 = 0 to define whether comm loss causes ramp stop / E-stop / fault. Verify on commissioning that the PLC-alive watchdog doesn't bring down production.
• Reference scaling: Danfoss parameter 3-02/3-03 minimum/maximum, Yaskawa uses b1-02..b1-05 and the SI-P3 mapping screen "Command Scale".

Step 5: Download and Commission

1. Compile the STEP 7 project. Resolve all warnings — unresolved symbols and DB length mismatches are the most common blockers.
2. Download Hardware Configuration only (this ensures the new SI-P3 slave is registered at the bus address) before downloading the program. After downloading, the diagnostic LEDs on the SI-P3 card should read BUS green, RDY/DRV green, and ERR off.
3. On the A1000 keypad: set F6-30 = n (n = DP node address), F6-01 = 1 (CE selection), F6-06 = Comm Loss Timeout. Set A1-03 = 2 (Initialize Parameters) only if you want a hard reset; otherwise back up with o2-03.
4. Verify on the A1000 with DriveWizard (Yaskawa PC tool) — the U6-01/U6-06 trace parameters show live control word, status word, and reference value coming in.
5. Stop the drive via PLC. Send 0x0000 as control word and a zero reference. Issue a drive run (0x001F) from the FB via STEP 7 online monitoring. Watch the actual frequency traverse the test profile.
6. Take a final S7 backup (Project → Archive) and a parameter backup from the A1000 (parameter o2-04 "Initialize SELECT"). Upload the A1000's parameter file via DriveWizard.

Verification Checklist

Test	Expected	Method
DP slave diagnosis	DP master shows slave online, no diag buffer entries	SIMATIC Manager → Online → Profibus → Diagnose Hardware
Cyclic PZD exchange	Status word updates once per DP cycle; reference written correctly	STEP 7 Monitor/Modify on SFC14 RECORD area
Control word preset "Run"	Drive enters RUN, output frequency rises per the ramp setting (C1-01 accel time)	Online monitor + amp clamp or Yaskawa U1-01
Stop / coast behavior	Sending 0x0007 (transition from run to coast) halts output within the configured decel ramp	Online monitor + drive display
Communication loss	Drive executes F6-01 reaction (e-stop / ramp / continue). PLC correctly raises COM_LOSS_DRV alarm	Pull the Profibus cable during run and verify
PKW round trip	Read parameter b1-01 (reference select) — value returned matches drive keypad	STEP 7 variable table against U1-xx
Endurance / 1-hour run	No DP faults, no excessive alarms, motor speed stable within ±1%	Live trend recording in STEP 7

Troubleshooting Matrix

Symptom	Likely Cause	Fix
SF BUS LED on S7-400 module steady red after download	Configured slave address differs from SI-P3 DIP / F6-30	Match F6-30 to project; or set termination; check cable integrity
ERR LED blinks red on SI-P3	Station address conflict on bus or wrong PPO type selected	Check address uniqueness; re-select PPO type matching drive parameter settings
SFC14 RET_VAL = FFFF non-bus error	LADDR points outside slave range or inconsistent length set wrong	Verify address book matches HW Config; verify RECORD length matches slave PZD count
Drive ignores control word, displays "bb" or "CALL"	Drive is not in "control from comm" mode	Set b1-01 appropriately (commonly 0 for keypad, choose comm source); set b1-02 / b1-03 run/stop source to option
Motor runs but reference is wrong scale	Reference scaling mismatch (e.g., -10..+10 V vs. 0..+10 V vs. 0..100%)	Configure SI-P3 Command Scale (F6-33/34), Drive Reference (b1-04 / b5-01)
Status word b3 always reports "fault" despite no faults	Bit semantics differ from Danfoss CTW map	Cross-reference Yaskawa SI-P3 manual for status word mapping
PLC reports "Slave not found" after re-download	Old SFC14/SFC15 RET_VAL still tracking old address range	Update LADDR parameter on SFC14/SFC15 call to new configured base address

Notes on Drive Lifecycle and Future Retrofits

Danfoss Drives (now part of the Danfoss Power Electronics business unit, after the 2023 acquisition of Vacon by Danfoss Drives culminating in a brand-aligned portfolio of VACON^® and VLT^®) runs a lifecycle program called DrivePro^® Retrofit that helps with end-of-product replacements, but this typically applies to drive-to-drive replacements within the same product family. When the original drive is end-of-life and a third-party replacement (like Yaskawa A1000) is the field option, the FB-rewriting approach above is the engineering-correct path. Reference: Danfoss Low Voltage Drives for the broader lifecycle services landscape.

Final Field Notes

• Always back up the original STEP 7 program (Upload-from-CPU + Upload-Online for the S7-400 station) before deleting any objects.
• Keep a static parameter list of the original Danfoss drive (current setpoint scaling, ramp rates, brake behavior, slip comp, etc.) to compare with the A1000 equivalents — most settings have direct counterparts but parameters are renumbered.
• Validate the new drive's E-stop category and STO (Safe Torque Off) wiring. Yaskawa A1000 supports STO via terminal inputs; do not rely solely on the bus control word for safety.
• If multiple drives are on the same Profibus segment, the master project must reflect the new device for only the migrated node; remaining drives remain unchanged.

Frequently Asked Questions