Harmac Software: Harmonics Calculation for Siemens Drives

1. Overview

Harmac was a Windows-based harmonics analysis utility developed by the Siemens US drives engineering team roughly a decade before the deprecation of its public download link. Its purpose was narrow but well-defined: build a model of an industrial power system containing a population of Siemens variable frequency drives, calculate the total harmonic distortion (THD) the drives inject back into the supply, and report whether the resulting bus complies with IEEE 519-2014 (and the 1992 revision that was current at the time of release).

The application was a single-machine, single-bus study tool rather than a full power-system simulation. It did not perform load flow, short-circuit, or transient analysis; it computed only the harmonic current spectrum of each drive, summed the bus voltages, and compared the result to the recommended limits in the standard.

2. Harmac Software Architecture and Function

The Harmac executable runs as a 32-bit Windows application and does not require a network connection or licensing server. The modeling approach is intentionally simplified so that a field engineer can answer a single question in a few minutes:

1. Define the source transformer (kVA, %Z, primary/secondary voltage, primary fault level).
2. Add the drive count and model family.
3. Enter the cable and bus impedance to the point of common coupling (PCC).
4. Run the harmonic calculation.
5. Read the THD values and per-order spectrum at the PCC.

Internally Harmac uses a Norton-equivalent current-source model for each drive: the rectifier is treated as a harmonic current source, with magnitudes read from a static table indexed by drive family, frame size, and operating point. The tables are populated from laboratory measurements of Masterdrives 6SE70/6SE71 units at 480 V and 575 V. The bus voltage distortion is then computed by linear superposition of these sources against the network impedance (transformer + cable) at each harmonic order.

3. IEEE 519 Compliance Methodology

Harmac reports compliance against the IEEE 519-2014 Recommended Practice and Requirements for Harmonic Control in Electric Power Systems. The two limits that matter for a drive-only study are:

The current limits from the same standard depend on the short-circuit ratio Isc/IL at the PCC and are documented in §5.1 of IEEE 519-2014. Harmac applies the current limits when the user enters transformer impedance and load kVA; otherwise only the voltage limits are evaluated.

4. Masterdrives Harmonic Models

The Harmac model library is keyed to the Masterdrives VC (Vector Control, 6SE70) and Masterdrives MC (Motion Control, 6SE71) families with 6-pulse rectifiers. The default model assumes:

• 6-pulse diode rectifier input (no active line filter, no 12-pulse option)
• DC link with no reactor beyond the standard bus capacitor
• Continuous operation at 100% load current
• Balanced 3-phase source

For 12-pulse Masterdrives the user selects a 12-pulse rectifier; Harmac then cancels the 5th and 7th harmonics and significantly reduces the 11th and 13th. Active line modules (Active Line Interface, ALI) and clean power filters (CBM, AFE) are not modeled — Harmac was released before these topologies were common on Masterdrives.

Typical Masterdrives 6SE70 harmonic current spectrum (480 V, 6-pulse, % of fundamental)

Total demand distortion (TDD) for a single 6-pulse Masterdrive at 100% load is typically 35–45 %; THDv at the drive terminals is usually 3–5 %. Numbers move with transformer impedance: lower %Z stiffens the bus and reduces voltage distortion but does not change the current spectrum.

5. Micromaster and SINAMICS Compatibility

Harmac does not contain a measured harmonic model for the MICROMASTER 4 (MM4) family. Attempting to load a MM4 project produces either a "model not found" warning or, depending on version, silently substitutes a Masterdrives profile, which is inaccurate. The MM4 rectifier topology is similar to Masterdrives (6-pulse, B6U bridge) but the DC link inductance is different, the IGBT switching produces a different high-frequency signature, and the controlled-cooling fan contributes a 3rd-harmonic injection at low speeds that Masterdrives does not exhibit.

The SINAMICS V20, G120, G120C, G130, G150, S110, S120, S150, and V90 families are not in the Harmac library at all. SINAMICS drives with a standard 6-pulse rectifier behave similarly to MM4 at the fundamental switching level but include optional line filters (B84143 series) and active line modules (ALM/SLM) that change the spectrum significantly. Harmac will not model these options.

6. SIZER Migration Path for Harmonics Analysis

SIZER is the current Siemens engineering tool for drive selection and system engineering, and it includes a harmonics module that is the direct functional replacement for Harmac. SIZER is available from the Siemens Industry Online Support portal and supports Windows 10/11. The harmonic analysis engine in SIZER handles:

• SINAMICS V20, G110, G120, G120C, G120P, G130, G150, S110, S120, S150, V90
• MICROMASTER 4 (with a reduced-fidelity model)
• Legacy Masterdrives (still supported for spare-part projects)
• 6-pulse, 12-pulse, 18-pulse, AFE, and basic LCL filter topologies

The workflow is the same as Harmac: define the network, add the drive population, evaluate. SIZER additionally outputs a per-order bar chart of Ih/IL and a pass/fail summary against IEEE 519 and G5/4.

SIZER vs. Harmac feature comparison

7. Alternative Tools: PATH Plus and Energy Analysis

PATH Plus (Power System Analysis Tool with Harmonics) is a free utility from Siemens that performs load flow, short-circuit, and basic harmonic analysis. The harmonic module is less detailed than Harmac — it uses generic 6-pulse profiles rather than measured Masterdrives data — but it does run on Windows 10 and is still distributed.

Energy Analysis (formerly SinaSave Energy Analysis) is a different class of tool: it estimates energy consumption and cost over a duty cycle rather than calculating harmonic distortion. It is not a substitute for Harmac or SIZER when IEEE 519 compliance is the deliverable. It is useful only for the energy-cost side of a project that also needs a harmonic study.

Third-party options for code-mandated harmonic studies include ETAP, SKM Power Tools, and DIgSILENT PowerFactory, all of which can import manufacturer harmonic data sheets and apply the same IEEE 519 evaluation. These are the standard tools for utility-interconnected studies in the US and are acceptable to most authorities having jurisdiction (AHJs).

8. Harmonic Calculation Formulas and Parameters

For a single 6-pulse drive the per-phase harmonic current amplitude is read from the manufacturer table; the bus voltage at order h is then

Vh = h · Zbus(h) · Ih

where Zbus(h) is the magnitude of the network impedance at the harmonic frequency, including transformer and cable. For a transformer, the impedance scales linearly with frequency:

Zbus(h) = Rtx + j·h·Xtx

Total harmonic distortion of the bus voltage is the RSS sum over all considered orders:

THDv = sqrt( Σ Vh² ) / V1 · 100%

Total demand distortion (current) is the RSS sum of the per-order current harmonics expressed as a percentage of the maximum demand load current IL, evaluated at the worst-case operating point (typically the highest running load):

TDD = sqrt( Σ Ih² ) / IL · 100%

For a parallel group of n identical drives, Harmac (and SIZER) combine the harmonics with a diversity factor kd(h):

Ih,group = kd(h) · sqrt(n) · Ih,single

with kd(5) = 0.9, kd(7) = 0.85, kd(11) = 0.8, kd(13) = 0.75, and kd(h) = 0.7 for h ≥ 17. Identical drives running in lockstep (same speed reference, same load) have kd approaching 1.0; independently controlled drives have kd approaching the values above.

9. Drive Input Current Harmonic Spectrum Reference

The following typical per-order values can be used to sanity-check a Harmac or SIZER output for a 480 V 6-pulse drive at 100% load, 60 Hz source, 5% source impedance:

The line filter reduces the low-order harmonics by roughly a factor of 4–5 but does not eliminate them. To meet the 5%/8% IEEE 519 limits on a stiff bus, a passive line filter plus 5–6% line reactor is usually the minimum configuration; active front ends (AFE/ALM) are required when bus voltage is already near the limit.

10. Field Commissioning Notes

When a Harmac or SIZER study predicts borderline IEEE 519 compliance, always verify in the field with a power-quality analyzer (Fluke 435, Dranetz HDPQ, Hioki PW3198). The measurement should be taken at the PCC defined in the model, with all drives running at the worst-case load identified in the study.

1. Set the analyzer to capture at least 30 cycles of steady-state data with a 10-minute averaging window.
2. Record THDv, TDD, and per-order harmonics from h = 2 to h = 50.
3. Compare measured Ih to the Harmac/SIZER predicted value. A deviation greater than 20% indicates either a transformer impedance mismatch, a capacitor bank interaction, or a non-linear load not in the model.
4. If TDD is below the IEEE 519 current limit and THDv is below the voltage limit, the system is compliant regardless of individual harmonic order magnitudes.
5. If THDv exceeds the voltage limit, the corrective action sequence is: (a) de-tune any switched capacitor banks away from the dominant harmonic, (b) add a passive line filter at the drive input, (c) upgrade to a 12-pulse or AFE rectifier.

11. Verification and Cross-Check Procedure

For a documented IEEE 519 study, the deliverables should include:

1. A one-line of the modeled system with the transformer kVA, %Z, and source fault level.
2. The Harmac or SIZER input file (or its printout) listing every drive, model, frame, and operating point.
3. The output table showing per-order bus voltage and current harmonic magnitudes.
4. A pass/fail statement against the appropriate IEEE 519 table for the bus voltage class.
5. For utility interconnection, a TDD evaluation at the POC (point of common coupling with the utility) and confirmation that the utility's own harmonic limits are met.

When porting an old Harmac study to SIZER, the expected deviation between the two outputs is typically ±5 % for the dominant orders (5th, 7th, 11th) on a Masterdrives system, because SIZER uses an updated Masterdrives profile that reflects the late-2000s hardware revisions. A larger deviation indicates either an incorrect transformer entry or a load not represented in the original model.

12. Quick Selection Guide

FAQ