Siemens MM440 and SINAMICS G120 1 Hz/Second Ramp Rate

Overview

Engineers controlling large positive-displacement blowers such as the Aerzen Delta series (200 kW class) with Siemens MICROMASTER 440 and SINAMICS G120 drives frequently need to separate the initial acceleration ramp from the subsequent PID-controlled setpoint tracking. The requirement in this application is straightforward: the drive should accelerate normally to the operating point during the initial ramp, and after that point every additional 1 Hz of frequency gain or 1 Hz of frequency loss should take one full second. This is a rate-of-change limit, not a single ramp time, and it is the right approach for blowers where mechanical surge at low frequency, oil-seal thermal stress, and acoustic pulsation must be avoided.

This reference walks through the parameter set on both drive families, the role of rounding (P1130 to P1133 in MM440, p1130 to p1133 in SINAMICS G120), the use of PID output limits and the integral time constant (P2285 / p2285) to enforce the 1 Hz/s behavior, the STARTER and TIA Portal commissioning procedure, and the verification steps needed before hand-over to operations.

Prerequisites

• Drive firmware verified: MM440 at least FW 3.2 (CPU1) for the full parameter set described; G120 with CU240B-2 / CU240E-2 / CU250S-2 control unit at FW 4.7 SP10 or higher.
• STARTER V5.4 SP1 or TIA Portal V15.1 or newer with SINAMICS Startdrive V15.1.
• USB or RS485 cable (MM440) and PROFINET/Ethernet (G120) for online commissioning.
• PLC providing the master process setpoint or feedback (typically S7-1200, S7-1500, or third-party PLC).
• Pressure transducer or flow transmitter 4 to 20 mA / 0 to 10 V wired to the analogue input used as PID feedback (MM440: ADC1 / ADC2; G120: AI0 / AI1).
• Blower nameplate data: rated power, rated speed, minimum continuous frequency (typically 20 Hz for Aerzen Delta positive-displacement units), and maximum permissible frequency.

Understanding the Ramp Structure on MM440 and SINAMICS G120

Both the MM440 and the SINAMICS G120 share the same ramp generator topology. The setpoint frequency reference is processed through a ramp function generator (RFG) that uses four editable segments:

1. Initial rounding (ramp-up) – P1130 / p1130
2. Ramp-up linear slope – controlled by P1120 / p1120
3. Final rounding (ramp-up) – P1131 / p1131
4. Final rounding (ramp-down) – P1133 / p1133
5. Initial rounding (ramp-down) – P1132 / p1132
6. Ramp-down linear slope – controlled by P1121 / p1121

P1120 (ramp-up time) defines the linear portion: the time to accelerate from 0 Hz to P1082 (maximum frequency). For a 50 Hz motor with P1120 = 10 s, the linear slope is 5 Hz/s. If the application needs the drive to reach setpoint quickly but then track at 1 Hz/s for further corrections, the linear slope must be set conservatively and the rounding parameters tuned to provide the slower rate during the bulk of the run.

On both families, the rounding type parameter P1134 / p1134 = 0 selects continuous smoothing (the rounded portion is added to the linear ramp time), while P1134 / p1134 = 1 selects discontinuous smoothing (the rounded portion is subtracted from the linear ramp time). For blower service, continuous smoothing (0) is almost always the correct choice because it avoids abrupt torque transients.

Parameter Mapping: Ramp-Up, Ramp-Down, and Smoothing

The reasoning behind the long P1131 (final rounding ramp-up) is critical. With P1120 = 25 s and P1082 = 50 Hz, the linear slope is 2 Hz/s. With P1131 = 20 s, the drive spends the last 20 seconds of the approach to setpoint in an S-curve that progressively slows the rate of change to nearly zero as it arrives at the target. The effective rate during this final segment can be tuned to land very close to 1 Hz/s, which is exactly the post-ramp behavior the application calls for.

To verify: with P1120 = 25 s and P1131 = 20 s on a 50 Hz base, the drive reaches the setpoint at approximately t = 32 s, and the last 10 Hz are covered in roughly 10 s, giving an effective rate of 1 Hz/s in the upper portion. Adjust P1131 to fine-tune this rate.

Implementing the 1 Hz/s Rate Using Rounding

The most reproducible way to achieve "each Hz takes 1 s after the acceleration ramp" is to define two conceptual zones:

1. Acceleration zone: 0 Hz to operating minimum (e.g., 0 to 25 Hz) governed by P1120 / p1120.
2. Tracking zone: 25 Hz to 50 Hz governed by P1131 / p1131 final rounding so that every additional Hz takes approximately 1 second.

For tracking zone, target frequency F and current frequency f_c, with P1131 set such that:

For a 1 Hz/s rate in the tracking zone when F − f_c = 5 Hz:

However, in practice the rounding curve is non-linear (parabolic), so empirical tuning is expected. Use the STARTER trace function or TIA Portal trace to record r0024 (output frequency) and r0020 (setpoint frequency), then iterate P1131 until the slope in the tracking zone matches 1 Hz/s.

PID Controller Configuration for Blower Pressure Control

For PID-driven setpoint tracking on Aerzen blowers, the PID output must also be rate-limited. Even with perfect ramp tuning, an aggressive PID can command large step changes that propagate through the RFG and cause the motor to overshoot or surge.

The integral time P2285 / p2285 is the principal parameter that controls how fast the PID output slews. With P2285 = 30 s and a step error of 5 %, the integrator will accumulate and produce a steady change of approximately 5/30 ≈ 0.17 %/s. With a full-scale frequency range of 50 Hz, that translates to roughly 0.08 Hz/s — too slow. With P2285 = 5 s, the integrator slews at about 1 %/s = 0.5 Hz/s — still below 1 Hz/s.

For exactly 1 Hz/s, set P2285 = (error span in %)/(1 Hz/s × 100 % / max Hz):

Operationally, start with P2285 = 5 s, observe, and reduce carefully. If the PID starts oscillating, increase P2285 or reduce P2280.

STARTER and TIA Portal Commissioning Procedure

STARTER (MM440 or G120)

1. Connect via RS485 (MM440) or PROFINET (G120) and go online.
2. Open the parameter list and apply the values from the table above.
3. Save to RAM, then perform a "Copy RAM to ROM" (icon on the toolbar) so the values survive a power cycle.
4. Open the trace recorder, add r0020 (setpoint frequency), r0024 (output frequency), r0026 (DC link voltage), and r0063 (actual speed).
5. Run the drive from 0 Hz to 50 Hz and back. Confirm visually that the final segment of the ramp-up exhibits a slope of approximately 1 Hz/s.

TIA Portal with Startdrive (G120)

1. Add the SINAMICS G120 device to the project, configure the control unit, and go online.
2. Navigate to "Parameters" and edit p1120, p1121, p1130 to p1134, p1080, p1082.
3. For PID, enable the technology controller and configure p2200 = 1.
4. Use the trace viewer to capture the same signals as in STARTER.
5. Save the project to the drive's memory card if used; otherwise perform "Save in the drive".

Alternative: PLC-Based Rate Limiting

When two drives (one MM440, one G120) must be coordinated, or when the operator requires different rates during different process phases (for example, faster rate during startup, slower rate during normal PID control), the PLC is often the better place to enforce the 1 Hz/s rule.

A SCL block for an S7-1200/S7-1500 PLC can implement a rate limiter on the speed setpoint sent to the drive:

IF ActualFrequency < SetpointFrequency THEN
    SetpointFrequency := MIN(SetpointFrequency, ActualFrequency + 1.0 * CycleTime);
ELSE
    SetpointFrequency := MAX(SetpointFrequency, ActualFrequency − 1.0 * CycleTime);
END_IF;

Where CycleTime is the PLC scan time in seconds (typically 0.1 s for OB1). This guarantees a 1 Hz/s slew rate regardless of PID activity inside the drive. In this topology, the drive's own ramps can be set short (P1120 / p1120 = 5 s) because the PLC limits the setpoint change, eliminating the need to tune P1131 for the post-ramp behavior.

Verification and Acceptance Test

1. Step response: Command a 10 Hz step from 30 Hz to 40 Hz. The drive should reach 40 Hz in approximately 10 ± 1 seconds.
2. PID stability: With the process running at steady state, induce a 5 % disturbance in the feedback signal. Observe r0024 settles within two minutes with no more than one oscillation.
3. Blower surge check: Monitor the blower discharge pressure and current. Confirm that the drive never operates below P1080 / p1080 (typically 20 Hz for Aerzen Delta units).
4. Thermal check: After 1 hour of operation, check the drive heatsink temperature (r0037). It must remain below the warning threshold (typically 90 % of the alarm threshold).
5. Acoustic check: Listen for pulsation or surge noise. If present, increase P1080 / p1080 by 2 Hz and reduce P2285 / p2285 by 1 s.

Troubleshooting Matrix

Field-Commissioning Notes Specific to Aerzen Delta 200 kW Blowers

Aerzen positive-displacement blowers have a characteristic that distinguishes them from centrifugal compressors: the delivered flow is essentially proportional to speed and largely independent of discharge pressure. This means the PID loop sees a process gain that does not change with load, simplifying tuning. However, two constraints are unique:

1. Minimum speed limit: Aerzen specifies a minimum continuous speed, typically 1500 to 1800 rpm depending on frame size. For a 4-pole motor, this corresponds to 25 to 30 Hz on the supply side. Set P1080 / p1080 accordingly; never let the drive command below this value, even briefly.
2. Thermal shock to the rotor: Cold starts with rapid acceleration cause differential thermal expansion in the rotors. P1120 / p1120 should be at least 20 s for a 200 kW unit. Cold-start P1131 / p1131 should be longer than warm-start P1131 / p1131 by approximately 30 %.
3. Acoustic noise: The Aerzen Delta uses internal pulsation dampers. Below 30 Hz, the damper geometry is less effective. If the application requires operating below 30 Hz, install an external acoustic enclosure or limit operation to above 30 Hz.

Summary of Recommended Parameter Set

For a typical Aerzen Delta 200 kW blower controlled by MM440 or SINAMICS G120 with the goal of "1 Hz per second after the acceleration ramp":

• P1080 / p1080 = 20 Hz (or per Aerzen nameplate)
• P1082 / p1082 = 50 Hz (or per motor nameplate)
• P1120 / p1120 = 20 s
• P1121 / p1121 = 30 s
• P1130 / p1130 = 5 s
• P1131 / p1131 = 20 s (this is the parameter that produces the 1 Hz/s approach rate)
• P1132 / p1132 = 5 s
• P1133 / p1133 = 20 s
• P2200 / p2200 = 1 (PID enabled)
• P2285 / p2285 = 5 s (start here; adjust to taste)

FAQ