Overview: Master Drive MC Parameterization Context
The SIMOVERT Master Drive Motion Control (MC) platform uses a connector/binector-based parameterization model in which every speed-dependent signal in the closed-loop control structure is normalized against a single reference quantity. Two parameters anchor this normalization for the speed and position control paths: P205 (rated speed for position control) and P353 (reference speed). Misalignment between these two parameters is one of the most common sources of gain drift, position-following error, and overspeed faults on retrofitted Master Drive MC axes.
This reference consolidates the parameter definitions from the SIMOVERT Master Drive Motion Control parameter list and the relevant function diagrams (FD 330 actual-value weighting and FD 340.3 position-controller reference/feedback), then walks through the calculation, indexing, scaling, and commissioning checks needed to deploy them on rotary axes.
P205 — Rated Speed for Position Control
P205 defines the motor speed that corresponds to 100 % of the position-control actual value. The unit is 1000 LU/min (length units per minute) — functionally identical to mm/min when the mechanical linear units and rotary-to-linear conversion have been pre-scaled into the LU domain. The factory default of 12288 (i.e. 12 288 000 LU/min, or 12 288 m/min equivalent) reflects the default motor configuration:
- Default motor rated speed
P108 = 3000 rpm - Default position resolution
P171 = 12→ 2^12 = 4096 increments per revolution - Default actual-value weighting factor AVWF = 1.0 (set via
P169andP170)
The published formula is:
P205 = (2^P171 × P108) / 1000 [unit: 1000 LU/min]For the default configuration this evaluates to (4096 × 3000) / 1000 = 12288.
Why P205 Exists Separately from P108
The motor nameplate speed (P108) describes what the motor can deliver; P205 describes what the position controller expects to see at its 100 % reference point. When a gearbox, leadscrew, or position-resolution change is introduced between the motor shaft and the load, only P205 is re-calculated; the underlying P108 value remains the motor's electrical/thermal speed limit.
Reading Non-Default P205 Values
The non-default P205 values reported in practice (368 968 for motor 1 and 437 387 for motor 2) are not raw rpm counts. They are 1000 LU/min quantities that already include the resolved position scaling of each individual motor/encoder combination. Working backwards from a non-default P205 recovers the implied product 2^P171 × P108:
| Motor | P205 reported | Implied 2^P171 × P108 | Diagnostic interpretation |
|---|---|---|---|
| Motor 1 | 368 968 | 368 968 000 | Higher encoder resolution and/or rated speed than default |
| Motor 2 | 437 387 | 437 387 000 | Higher rated speed and/or finer resolution still |
The difference between the two motor entries (≈68 419 increments of 1000 LU/min, or roughly 18.5 %) tells the engineer that motor 2 has either a higher nameplate speed, finer encoder resolution, or a non-unity AVWF relative to motor 1 — it is not a parameter error, it is the auto-calculated P205 for that motor's data set.
P205 directly without re-deriving it from P108, P171, and the AVWF. Manually punching a value into P205 without updating the scaling chain it represents produces a position loop whose KV factor silently doubles or halves.P353 — Reference Speed for Normalization
P353 is the parameter against which all speed variables in the drive are normalized. Its value corresponds to a connector value of 4000 H (hex), i.e. 100 % in the SIMOVERT dual-format (hex/decimal) connector representation. The closed-loop control structure can process up to 2 × P353 as the upper end of its linear operating range; values above this enter saturation.
P353 Index Structure
Because the reference speed often contains fractional rpm values, P353 is split into two indices:
| Index | Meaning | Range | Notes |
|---|---|---|---|
| P353.01 | Integer part of reference speed (rpm) | 1 ... drive-dependent max | Zero is not permitted — the drive rejects P353 = 0 |
| P353.02 | Fractional part of reference speed, four decimal places | 0 ... 9999 | Pad with leading zeros; 1234.0120 → 0120 |
Worked Index Examples
| Desired reference speed | P353.01 | P353.02 |
|---|---|---|
| 1234 rpm exact | 1234 | 0000 |
| 1234.5 rpm | 1234 | 5000 |
| 1234.123 rpm | 1234 | 1230 |
| 1234.0120 rpm | 1234 | 0120 |
Always pad fractional values to four digits — the drive parser does not auto-zero-extend. For most rotary axes the integer-only entry (P353.02 = 0000) is sufficient.
P353 also rescales the speed limits (P504 family) and the ramp reference. Never change P353 alone — update P352 (frequency reference) by the same integer multiple, update P205 by the inverse multiple to keep the position-loop KV constant, then verify with a low-speed jog.Relationship Between P205 and P353
Both parameters describe a speed in rpm, but they serve different scaling domains:
| Aspect | P205 | P353 |
|---|---|---|
| What it normalizes | Position-control actual value (LU domain) | All speed connectors (speed domain) |
| 100 % corresponds to | P205 in 1000 LU/min | P353 in rpm (= 4000 H) |
| Default value (factory) | 12288 (= 12 288 000 LU/min) | 3000 rpm |
| Affected by changing it | Position-loop KV factor | Speed limits, ramp times, all speed connectors |
Coupling Rule (From the Parameter List)
The Master Drive MC parameter list states explicitly: "The reference variable for frequency (P352) or speed (P353) should just be changed with the same integer multiple number. The effective n-regulation will be changed by the same factor. The position control amplifier will be increased by the reverse of this factor. The rated speed for position control P205 has to be changed by this factor to enable the effective position control gain to remain."
Translating that into algebra, if you scale P353 by integer factor k:
- Multiply
P352byk - The speed regulator (n-controller) gain scales by
k - The position controller gain scales by
1/k(i.e. it decreases) - To hold effective position KV constant → multiply
P205byk
Numerical Example — Doubling the Reference Speed
Starting from the default P353 = 3000 rpm, suppose the application requires a 6000 rpm reference (high-speed spindle repositioning):
- Set
P353.01 = 6000,P353.02 = 0000 - Set
P352(frequency reference) from 50.00 Hz default to 100.00 Hz (same integer multiple k = 2) - Multiply
P205by 2 →P205 = 24576 - The n-controller (KV_n) now acts twice as aggressively at the same % reference
- The position controller (KV_s) acts half as aggressively at the same % reference — this is exactly compensated by the P205 doubling, so the closed-loop KV stays identical
Function Diagram References
| Function Diagram | Content | Parameters shown |
|---|---|---|
| FD 330 | Actual-value weighting (AVWF) | P169, P170, scaling factors for motor/load |
| FD 340.3 | Position controller reference/feedback path | P205, P171, position resolution |
| FD 170 | Speed setpoint channel | P352, P353, ramp generator references |
| FD 200 | Speed limiting | P504 family, derived from P353 |
Always cross-reference FD 330 and FD 340.3 when changing either P205 or P353; both diagrams must be reviewed to confirm there are no parallel scaling blocks that would otherwise be missed.
Parameter Interdependency Map
Commissioning Procedure
-
Capture motor nameplate data. Record
P108(rated speed), encoder type, and any gearbox ratio. Save to drive parameter file via DriveMonitor / SIMOVIS. -
Set encoder resolution. Configure
P171to the encoder line count exponent so that2^P171= increments per motor revolution. For a 4096 incr/rev encoder → P171 = 12. -
Configure actual-value weighting. Set
P169(numerator) andP170(denominator) to encode the gearbox ratio and load-side scaling. The resulting AVWF = P169/P170. -
Compute P205. Use the formula
P205 = (2^P171 × P108) / 1000. Verify against the value auto-calculated by the drive during motor identification, where supported. -
Set P353. Enter the reference speed into
P353.01(integer) andP353.02(fractional × 10 000). Pad P353.02 with leading zeros. Verify P353 ≠ 0. -
Couple P352. Scale
P352by the same integer multiple as P353 was changed from its factory value. - Recompute P205 if P353 was scaled. Multiply the P205 from step 4 by the scaling factor k from step 6.
- Verify position loop. Issue a 1-revolution index move; check that the drive reports the same LU count as the encoder (4096 for the default).
- Verify speed loop. Command 100 % speed setpoint; the drive should ramp to P353 rpm (within tolerance) without overspeed or speed-controller-at-limit alarms.
- Save and back up. Upload the parameter set via DriveMonitor or SIMOVIS. Store in the machine documentation folder.
Verification Checks
| Check | Expected result | Fault symptom if wrong |
|---|---|---|
| Read P205 on PMU | Matches formula output exactly | Drift = wrong P171 or AVWF |
| Read P353.01 / P353.02 | P353.02 padded to 4 digits | Normalization error = wrong P353.02 padding |
| Index move of 1 motor revolution | Position actual advances 2^P171 LU | Mismatch = P205 or AVWF wrong |
| Command 50 % speed | Motor runs at 0.5 × P353 rpm | Wrong speed = P353 scaling wrong |
| Overspeed alarm at 110 % setpoint | Triggers at 1.1 × P353 | Late/no trip = P504 limits not coupled |
| Position loop following error at 1000 mm/min | Same as before parameter change (if KV preserved) | Increased following error = P205 not rescaled with P353 |
Troubleshooting Matrix
| Symptom | Likely root cause | Corrective action |
|---|---|---|
| Position loop oscillates after motor change | P205 not recomputed for new P171 | Recompute P205 = (2^P171 × P108) / 1000 |
| Drive faults overspeed at low commanded speed | P353 scaled down without P205 scaling | Apply k-factor coupling rule to P205 and P352 |
| Speed actual reads wrong by integer factor | P353.02 padded incorrectly | Pad P353.02 to 4 digits with leading zeros |
| Following error grows with speed | P205 and P353 out of coupling | Recompute P205 = k × old P205 |
| Speed limits (P504) don't match commanded max | P353 changed without re-deriving P504 | Recompute P504 family from new P353 |
| Position KV suddenly halved after commissioning | P205 doubled (k=2) but P171 not changed | Verify 2^P171 and P108 still match the formula |
| Encoder/feedback fault at high speed only | P205 too high → position loop demands impossible rate | Verify mechanical max speed vs. P205 / 1000 |
| Drive rejects parameter download | P353 = 0 | Enter a non-zero P353.01 value |
Edge Cases and Field-Proven Pitfalls
-
Hex-vs-decimal confusion: PMU displays of
4000 Hmean 100 % in 16-bit hex (16384 decimal). Do not convert P353 to hex when reading PMU — it is already normalized in hex-percent. - Zero P353: The drive rejects P353 = 0 because that would make every speed connector undefined. If a "speed setpoint invalid" or similar alarm appears after parameter upload, P353 is the first parameter to inspect.
- Motor data set switch-over: When switching between motor 1 and motor 2 data sets (e.g. via a motor-selection parameter in the P36x family), P205 is also switched. Verify that both motor P205 values are individually correct — this is why field installations show P205 = 368 968 for motor 1 and 437 387 for motor 2.
-
P205 unit awareness: The unit is
1000 LU/min. A value of 368 968 corresponds to 368 968 000 LU/min, which for a default AVWF of 1.0 implies a motor/encoder combination of (368 968 × 1000 / 4096) ≈ 90 078 rpm if P171 = 12 — clearly the AVWF must be non-unity for this to make sense in a real installation. - Firmware index behaviour: Older parameter lists treat P353 as a single value. Later MC firmware revisions split the parameter into P353.01 and P353.02 for higher-resolution entry. Confirm the parameter-list version of the connected drive before commissioning.
- Rotary vs linear axis scaling: The formula assumes rotary LU; if the downstream axis is a linear stage with a leadscrew, an additional mm-per-revolution factor must enter the AVWF (P169/P170) — do not fold it into P205 directly.
- Backup before any change: Always upload the parameter set to DriveMonitor/SIMOVIS before editing P205 or P353. A mis-scaled normalization cannot be undone by editing a single parameter.
Related Parameters at a Glance
| Parameter | Function | Coupled with |
|---|---|---|
| P108 | Motor rated speed (rpm) | P205 via formula |
| P169 / P170 | AVWF numerator / denominator | P205 scaling |
| P171 | Position resolution exponent (2^P171 incr/rev) | P205 formula |
| P205 | Rated speed for position control (1000 LU/min) | P108, P171, AVWF, P353 |
| P352 | Frequency reference normalization (Hz) | P353 by same k-factor |
| P353.01 / P353.02 | Reference speed normalization (rpm + fractional) | P352, P205, P504 family |
| P504 family | Speed limits (positive, negative, absolute) | Derived from P353 |
How do I calculate P205 for a non-default encoder resolution?
Use the formula P205 = (2^P171 × P108) / 1000. Set P171 to the exponent so that 2^P171 equals the encoder's increments per motor revolution (P171 = 12 for 4096 incr/rev, P171 = 13 for 8192 incr/rev). The result is in 1000 LU/min.
What happens if I change P353 without updating P205?
The position-loop gain changes by the inverse of the scaling factor. Doubling P353 without doubling P205 halves the effective KV, producing growing following error at high speed and possible position-controller faults.
Why does the drive reject P353 = 0?
The drive uses P353 as the normalization basis for every speed connector (4000 H = 100 %). A zero reference makes the percentage-to-rpm conversion undefined, so the firmware rejects the parameter download.
How do I enter a fractional reference speed into P353?
Use P353.01 for the integer rpm and P353.02 for the four-decimal fractional part (0–9999). For 1234.5 rpm set P353.01 = 1234 and P353.02 = 5000; pad the fractional with leading zeros (e.g. 1234.0120 → P353.02 = 0120).
Where do I find the canonical parameter list and function diagrams?
See the SIMOVERT Master Drives Motion Control Compendium for the full parameter, connector and binector list, and cross-reference function diagram 330 (AVWF) and 340.3 (position controller reference).