Powering SINUMERIK 840D NCU from Single-Phase 220VAC Supply

Problem Overview

Bench-testing a SINUMERIK 840D NCU (Numerical Control Unit) outside a machine cabinet is a recurring engineering task: validating NCK software, debugging PLC programs, replacing a defective NCU box, or reproducing a customer fault on a development desk. The practical problem is that the standard SIMODRIVE 611 E/R (Infeed/Regenerative) module, part number 6SN1145-1BA01-0BA1, is hard-wired for a three-phase 400 VAC (or 480 VAC class) industrial supply, while a typical engineering office supplies only single-phase 220–240 VAC phase-to-neutral. The electronics section of the NCU further requires a precise, low-noise DC bus and a 24 V logic rail generated by the SIMODRIVE 611 infrastructure, not by a generic lab supply.

This reference documents three field-proven paths to bring a 840D NCU up on a desk:

1. Use a single-phase to three-phase frequency inverter (Siemens Micromaster 420, part number 6SE6420-2UD...) to synthesise 3 × 400 V / 50 Hz from 1 × 230 V, then feed the E/R module normally.
2. Substitute a UEB control unit (also called UE-Modul) that generates the +5 V / +15 V / −15 V / +24 V rails from the 400 V rail without requiring the full line infeed section.
3. Power only the NCU electronics via connector X181 (24 V standby) and bypass the SIMODRIVE power section, accepting that SIMODRIVE axes will remain offline.

SINUMERIK 840D NCU Power Architecture

The SINUMERIK 840D sl NCU is supplied from the SIMODRIVE 611 modular drive system. Power flow from the wall to the NCU follows the chain:

1. Mains (3 × 400 VAC) → I/R (Infeed/Regenerative) module, e.g. 6SN1145-1BA01-0BA1.
2. DC bus (600 VDC nominal, ≈ 1.35 × √2 × 400 V) → distributed to Power Modules (axis inverters) and the UE/UEB control unit.
3. UE/UEB module → derives 24 V logic rail, +5 V, +15 V, −15 V for the NCU, HMI, handwheel, and PLC I/O.
4. 24 V at X181 / X172 → fans, NCU electronics, optional 24 V load outputs.

The full power-up sequence is documented in the SINUMERIK 840D sl NCU manual (the manual containing the recommended power supply units and tables for calculating power consumption for interconnection with SINAMICS S120 modules) at SINUMERIK 840D sl NCU documentation, Siemens Support (PDF).

E/R Module 6SN1145-1BA01-0BA1 — Why It Will Not Start on 1-Phase 220 V

The 6SN1145-1BA01-0BA1 is a 10 kW class I/R (Infeed/Regenerative) module for the SIMODRIVE 611 system. Its three-phase diode/thyristor rectifier section is designed for 3 × 400 VAC ±10 %, 50/60 Hz. Key constraints:

• Internal phase-loss detection trips the module within 100–200 ms if any of L1, L2, L3 is missing. The diagnostic LED group shows fault code F30002 (line phase failure) on the SIMODRIVE 611 family, and the unit refuses to close the pre-charge contactor.
• The DC-link pre-charge circuit assumes 3-phase energy storage; running it from 1-phase causes asymmetric DC bus voltage and the over-voltage comparator typically trips at ≈ 760 VDC.
• Even with the line terminals bridged (L2–L3 jumpered to Neutral) the input rectifier still cannot deliver rated DC bus current, and the E/R reports F30001 (line overcurrent) when a power module requests torque.

Conclusion: the 6SN1145-1BA01-0BA1 cannot be operated on 1 × 220 VAC. A 1-phase to 3-phase conversion must be added upstream of the E/R input terminals.

UEB Control Unit as an Alternative

The UEB (also called UE-Modul, part number family 6SN1145-1AA0x / 6SN1146-1AB0x) is the power-supply module that sits between the DC bus and the NCU. It performs three functions:

1. DC/DC conversion of the 600 VDC link to the +24 V / +15 V / −15 V / +5 V rails used by the NCU, HMI, and PLC.
2. Device bus communication (serial, ≈ 5 V logic) with the Power Modules and SIMODRIVE electronics.
3. 24 V input on X181 to back up the NCU memory and a small amount of logic when the DC bus is not energised.

If the test target is only the NCU box (no axis verification, no HMI advanced graphics), the UEB can be used in a degraded mode provided the 600 VDC link is present on its input. The 600 VDC can be supplied from a bench high-voltage supply (e.g. EA-PS 9080-510) set to 600 VDC, with current limit at ≈ 1 A to mimic a no-load line. This avoids the E/R module entirely and powers only the electronics section.

Path 1: Single-Phase 220 V → 3-Phase 400 V via Micromaster 420

The field-tested workaround is to drive a Siemens MICROMASTER 420 (MM420) in V/f mode from 1 × 230 V, configured to output 3 × 400 V / 50 Hz, then feed the E/R module's line input from the MM420 output. The MM420 must be a 1-phase 230 V class unit (frame size A or B), not the 3-phase 400 V class. Typical order codes for 0.75 kW to 4 kW:

The 1-phase 230 V input on a MM420 is internally doubled to a synthetic DC bus, and the inverter section can be re-parameterised to output 3 × 400 V at 50 Hz, even though the unit is normally sold for 230 V 3-phase output. The key insight is that the MM420 output voltage is software-defined by parameter P2000; the hardware range tolerates the requested frequency up to 650 Hz and voltage proportional to the DC bus, which on the 1-phase input yields a peak DC link around 320–340 V. The result is the inverter is asked to deliver 400 V line-to-line at 50 Hz from a 320 V DC link — the MM420's PWM control loops will regulate this only with reduced headroom.

For SIMODRIVE 611 E/R input voltage tolerance (400 VAC ±10 %, 47–63 Hz), the practical output of the MM420 must reach at least 360 V line-to-line. The MM420 will operate as a step-up only if the DC bus is charged by the rectifier to a peak above √2 × 230 V = 325 V. With the standard 1-phase input, the peak DC bus sits at ≈ 320 V, so 3 × 400 V output cannot be sustained; the unit must be de-rated. Therefore:

• Set P2000 = 360.0 (max output voltage) instead of 400 V to avoid DC bus under-voltage trips.
• Configure the E/R to accept the lower voltage by adjusting the internal transformer tap if available, or accept that the SIMODRIVE DC link will be ≈ 540 VDC instead of 600 VDC. The 840D NCU electronics operate down to ≈ 480 VDC, so this is acceptable for bench tests.

Wiring Diagram

Inline SVG topology of the test-bench power chain:

Required MM420 Parameter Set

Apply the following parameters via the operator panel (BOP) or STARTER commissioning software. The full parameter reference is in the MICROMASTER 420 Operating Instructions, which lists the complete parameter set; the values below are the minimum bench-test configuration.

Why the MM420 Inverter Works

Although the MM420 is sold as a motor inverter, its output stage is a standard three-phase IGBT bridge with a V/f (or vector) controller. The "load" in this application is the E/R input rectifier, which presents as a passive diode bridge plus a large electrolytic DC-link capacitor. After the initial inrush into the E/R's soft-charge resistors (pre-charge takes ≈ 1 s on the SIMODRIVE 611), the E/R looks like a stiff DC load drawing only the magnetising and housekeeping current of the SIMODRIVE system, typically under 1 A. The MM420 sees this as a 50 Hz no-load and locks into the configured V/f line. The E/R pre-charge closes its contactor, the internal DC bus rises to ≈ 540 VDC (with P2001 = 360 V input), and the UEB module generates all internal rails normally.

You must not run the SIMODRIVE axis Power Modules on this supply during test; their dynamic braking energy would push the DC bus voltage above the MM420's regen capacity, causing F0002 DC-link overvoltage. This is exactly why the bench-test path is intended for NCU and PLC verification only, not for axis motion.

Path 2: 24 V Only via X181

If the only goal is to verify that the NCU's NCK starts, the PLC boots, the CF card is read, and the HMI displays, the SIMODRIVE 611 can be bypassed entirely. Apply a regulated 24 VDC, ≥ 5 A supply on the X181 connector of the NCU. The X181 pinout on the SINUMERIK 840D sl NCU is:

Under 24 V-only the NCU's NCK will boot and stop at the "Drive not ready" state. Expected behaviour:

• Status LED on the NCU front panel: solid green after ≈ 30 s, then solid yellow/orange when the NCK waits for the drive bus.
• HMI boot screen on TCU/PCU; no axes visible.
• Alarms 025201, 025202, and 000124 "Drive: bus not initialised" will be raised.

This is the safest bench-test path: the bench-top 24 V supply carries the only current (max 5 A, 120 W), and the SIMODRIVE system is completely de-energised.

Step-by-Step Commissioning Procedure

1. Inventory the modules: NCU, UEB, E/R (6SN1145-1BA01-0BA1), MM420, and a regulated 24 VDC bench supply. Verify the MM420 is the 1-phase 230 V input variant.
2. Connect the 1 × 230 V office mains to the MM420 line input (L, N, PE). Bond PE to the E/R chassis ground stud at the E/R module.
3. Wire MM420 output U2 / V2 / W2 to E/R input U1 / V1 / W1 with insulated 4 mm² conductors, length ≤ 1 m. Phase rotation does not matter for a rectifier load.
4. Apply the MM420 parameter set above. Save with P0971 = 1.
5. Power up the 24 VDC supply on X181 of the NCU. Confirm the NCU front-panel LEDs enter the standard boot sequence.
6. Enable the MM420 output (close DIN1, or press the green button on the BOP). Allow the E/R pre-charge to complete (≈ 2 s). Verify the MM420 display shows 50.0 Hz, ≈ 1.0 A, and that the E/R status LED turns green.
7. Verify the UEB internal rails with a DMM on its test points: +5.10 V ± 2 %, +15.0 V ± 3 %, −15.0 V ± 3 %, +24.0 V ± 5 %.
8. Watch the NCU boot to the HMI; confirm the NCK reaches 7-segment display "6" (PLC ready) and waits for drive commissioning.
9. Run the desired NCK / PLC test. Do not enable any axis drive (no DB31, ... DBX21.0 = 1).

Verification Checklist

Troubleshooting Matrix

Safety Considerations

• DC bus voltage remains at ≈ 540 VDC for several minutes after mains disconnect. The E/R has internal discharge resistors sized to bring the bus below 50 V in ≈ 5 minutes. Always measure before contact.
• The MM420 output is not isolated from the mains; treat U2, V2, W2 with the same respect as 230 V mains conductors.
• Bonding: the PE of the office mains, the PE terminal of the MM420, and the chassis stud of the E/R must be on a common star point. Do not rely on a single conductor run.
• EMC: the MM420 output is PWM at 4 kHz. Place the E/R ≤ 1 m from the MM420 to keep the high-frequency loop area small, and route the DC bus under the module rather than through free air.
• Do not operate the bench test setup unattended. A fault in the SIMODRIVE pre-charge circuit can cause the MM420 to fold back, and the E/R can enter a regenerative mode if the DC bus is disturbed.

Comparison: Three Power-Up Paths

For a verification of NCK, PLC, and HMI, Path 1 is the most representative because the UEB is alive and the device bus is in its normal topology. Path 3 is the fastest for a CF-card swap or firmware update test.