SIMOREG 6RA70 Ride-Through with UPS: F006, P086, P361 Setup

SIMOREG 6RA70 Ride-Through with UPS: F006, P086, P361 Configuration

Configure a Siemens SIMOREG MASTER DC drive (6RA70 family, model 6RA7085-6DV62-0) for short-duration power-loss ride-through when fed through an Emerson/Vertiv NXA 200 kVA UPS in 1+1 parallel configuration. This reference covers the 10 ms voltage-failure window defined by parameter P086, the F006 line-failure fault path, the P361 restart coordination, and the Chapter 9.17 automatic restart logic needed to keep a 158 kW DC motor running through momentary mains disturbances without tripping the thyristor bridge.

1. Application Overview

A 6RA7085-6DV62-0 is a fully digital three-phase thyristor DC drive in the SIMOREG MASTER family, rated for armature currents up to 850 A and field excitation up to 30 A. The drive is the right candidate for a 158 kW DC motor: a 460 V class shunt-wound motor with 158 kW output draws on the order of 343 A armature (158 kW / 460 V) at full load, which sits well below the 850 A converter limit, leaving roughly 2.5x overload headroom for the standard 1.5x for 60 s / 1.8x for 30 s characteristic of the 6RA70.

The user's installation pairs the drive with two Emerson/Vertiv NXA 200 kVA double-conversion online UPS units running in parallel, for 400 kVA apparent / 320 kW real at the typical 0.8 power factor rating. The UPS bank is sized for 5 minutes of full-load autonomy. The technical question is whether the UPS can hold up the drive input during a short mains outage long enough that the SIMOREG never crosses its internal line-failure threshold, and which drive parameters need to be configured to exploit that ride-through window.

2. Why the SIMOREG Trips on Mains Loss

The 6RA70 is a phase-angle-controlled thyristor rectifier. Each thyristor pair on the three-phase bridge is line-commutated, meaning the device can only turn off when the AC line voltage reverses polarity across it. The firing pulses for the next device are synchronized to the line zero crossings. When the AC line collapses:

1. The armature current in the DC link inductor cannot freewheel through the supply; it continues through the load (armature + field + smoothing inductor).
2. After roughly 5-20 ms, the DC link voltage falls below the drive's undervoltage threshold (parameter U816 or the equivalent monitoring in the firmware build), and the controller raises fault F006 (line failure).
3. The drive pulses the thyristor gates off and the motor coasts to a stop under load, with the fault latched until manual or automatic reset.

The threshold of "when does the drive give up and raise F006" is the variable the user can adjust. It is governed by parameter P086 (line-failure time) in conjunction with the line-voltage monitoring defined in the firmware. A UPS that holds the AC bus within tolerance for the duration of P086 will be invisible to the drive: the drive never sees a fault, the thyristors continue to commutate, and the motor keeps running.

3. Sizing the UPS for a 158 kW DC Drive

The DC drive's AC input apparent power is governed by:

with η_drive at 0.96-0.98 and PF_drive strongly dependent on speed and load. The PF of a 6RA70 at full speed and full load is typically 0.85-0.90; at low speed it falls to 0.5-0.7 because the firing angle grows and displacement current dominates.

With two NXA 200 kVA units in parallel (400 kVA / 320 kW at PF 0.8), the UPS bank has roughly 1.6x to 2.1x headroom on the drive input at full speed, and only 0.75x margin at very low speed. The user's 320 kW real-power rating assumes a PF of 0.8, but the 6RA70's worst-case displacement can push the apparent power above the 320 kW real-power limit even though the actual watts stay below 158 kW. Two practical consequences:

• If the process forces the drive to hold low speed at full torque (e.g., a hoist at hold position), the apparent kVA climbs and the UPS may alarm on overload. In that case, derate the process or upsize the UPS.
• Regenerative overhauling loads (a descending hoist, a deceleration ramp) push real power back into the AC bus. The NXA double-conversion UPS must absorb this through its inverter section; verify with the Vertiv NXA documentation that the unit's bidirectional inverter handles the expected kW of regen for the process cycle.

4. Fault F006 - Line Failure

Fault F006 is the 6RA70's line-failure alarm. It is raised when the controller's line-voltage monitor (typically U816 or its firmware-build equivalent) detects a sustained undervoltage condition on the AC bus lasting longer than the time window defined by P086. With the UPS in the supply path:

• The UPS holds the AC bus within tolerance during the mains event (zero transfer time for a true online double-conversion UPS like the NXA).
• The drive's line-voltage monitor never crosses the undervoltage threshold.
• F006 is not raised; the drive continues to commutate normally.

The F006 path becomes relevant only when the UPS is bypassed, the UPS battery is depleted, or the mains event outlasts the UPS autonomy (5 minutes in the user's case). For events inside the ride-through window, the engineer can use P086 to define how long a true line disturbance the drive will absorb before giving up and raising F006.

5. Parameter P086 - Voltage-Failure / Ride-Through Time

P086 is the parameter that defines the line-failure ride-through time for the 6RA70. The 6RA70 manual describes P086 as the voltage-failure time window: a disturbance on the AC line shorter than P086 is treated as a transient and the drive continues to operate. A disturbance longer than P086 is interpreted as a line failure and the drive reacts according to the F006 path and the automatic-restart logic.

The user's discussion confirms a 10 ms setting for P086. Ten milliseconds is the standard engineering target for a thyristor DC drive:

• 10 ms covers a half-cycle of 50 Hz mains, which is the absolute minimum time the line-commutated bridge needs to find a new commutation point after a single-cycle disturbance.
• 10 ms is well within the ride-through capability of any double-conversion online UPS, including the Emerson/Vertiv NXA, which has zero transfer time.
• 10 ms is short enough that a true line outage lasting longer will not falsely keep the drive armed and risking an out-of-sync firing pulse.

Field-recommended settings for P086 in a UPS-backed installation:

6. Parameter P361 - Restart Coordination

P361 sits in the 6RA70 parameter tree as part of the restart and run-up logic. In the 6RA70 manual, P361 is the restart-waiting time that the controller inserts between the line coming back within tolerance and the drive re-energizing the thyristor bridge. Without this delay, the drive could re-fire the bridge on a partially stabilized bus and either:

1. Drop back into F006 if the bus collapses again, or
2. Inrush the supply transformer with a partially discharged DC link, tripping the upstream breaker.

With the UPS in the path, P361 is also a coordination parameter: the engineer sets P361 long enough to confirm the UPS is steady-state online (not still running on battery recovery), and short enough that the process restarts within an acceptable window. The user's discussion calls out P361 alongside P086; in practice, P361 typically ranges from 0.3 s to 3.0 s in a UPS-backed installation.

7. Automatic Restart Function (Chapter 9.17)

Chapter 9.17 of the 6RA70 operating instructions covers the automatic restart function. The user enables this chapter to allow the drive to recover from a line failure without operator intervention, which is the missing piece when P086 is set aggressively. With auto-restart enabled, the drive follows this sequence on detection of a recoverable line event:

1. Detect line undervoltage.
2. Wait for the disturbance to clear (P086 budget).
3. If disturbance cleared inside P086: continue firing pulses, motor keeps running.
4. If disturbance lasted longer than P086: latch F006, disable firing pulses, motor coasts.
5. Once line returns and stays within tolerance, start the auto-restart timer (P361).
6. When P361 expires, re-arm the thyristor bridge, pre-charge the DC link, ramp the motor back to its setpoint with the configured acceleration ramp.

Engineer field note: auto-restart is appropriate for a process that can tolerate an uncontrolled coast-down. It is not appropriate where the coast-down itself is hazardous (elevator, crane hoist with suspended load, fan with surge risk, conveyor with material on the belt). For those applications, do not enable Chapter 9.17; let F006 latch and require operator reset after verifying the process state.

8. Commissioning Procedure

The commissioning sequence for a UPS-backed 6RA70 ride-through installation runs in this order. The engineer should record the parameter set after each step.

1. Verify UPS installation. Confirm both NXA 200 kVA units are in online double-conversion mode, static bypass is healthy, battery string is at full charge, and paralleled output is load-shared correctly. The Emerson/Vertiv NXA panel will show a parallel-status indicator; both units must report a healthy parallel link.
2. Power the drive from the UPS output. Energize the 6RA70 from the UPS bus with the motor disconnected. Confirm three-phase voltage at the drive input is balanced and within the drive's tolerance (typically +/-10% of nominal).
3. Set the line monitoring threshold. Configure the drive's line undervoltage threshold (referenced in the manual as a U8xx or equivalent monitoring parameter in your firmware build) to a value below the UPS's worst-case output deviation but above the level that would damage the drive. This is the boundary the P086 timer watches.
4. Set P086 to 10 ms. This is the line-failure ride-through window. The drive treats any sub-10 ms disturbance as a transient and continues firing.
5. Set P361 to 1.0 s (or process-appropriate restart delay).
6. Enable Chapter 9.17 automatic restart. Configure the maximum restart attempts, the ramp time, and the enable condition (e.g., line healthy AND enable input present).
7. Connect the motor and run at no load. Verify the drive runs from the UPS bus, current limit, and field are healthy.
8. Run at full load. Apply the 158 kW mechanical load and let the drive stabilize. Record input kVA, kW, displacement PF, and UPS loading. Confirm UPS loading stays below 80% in all speed/torque points of the process cycle.
9. Backup the parameter set. Save to OP1S, DriveMonitor, or an automation software archive. Note the firmware version on the CU of the 6RA70.

9. Verification and Field Testing

A ride-through installation is not commissioned until the engineer has proven, on the running plant, that the drive survives a real mains event. Recommended test sequence:

1. Static-bypass transfer test (UPS-only). Force the UPS to static-bypass and back to inverter while the drive runs at no load. The AC bus should be continuous; the drive should not raise F006. If F006 fires here, the UPS is not as clean as the spec sheet claims, or the drive's line monitor is set too tight.
2. Mains-out simulation, 1 second. Open the upstream breaker feeding both UPS units. The UPS runs on battery; the drive sees no disturbance. Restore the breaker. The drive should not have raised F006 and should not have triggered P361 / auto-restart.
3. Mains-out simulation, 4 minutes (under 5-min autonomy). Open the breaker, run the drive on UPS battery for 4 minutes, then restore. The drive should ride through cleanly.
4. Mains-out, 6 minutes (over autonomy). Open the breaker, run past the 5-minute autonomy, let the UPS drop load. The drive should fire F006 and stop. This is the bounding test that proves the protection chain works when the UPS is exhausted.
5. Regenerative test. If the process has a regenerative load (hoist lowering, conveyor with descending material), run that portion of the cycle on UPS. Confirm the UPS absorbs the kW without alarm. The Emerson/Vertiv NXA spec sheet should be checked for its regenerative handling capability before this test.

For each test, capture the drive's fault buffer (read the F006 history via the OP1S or DriveMonitor), the UPS event log, and a clamp-meter reading of the input current at the drive. Save all traces against the test record.

10. Edge Cases and Caveats

A few field-proven caveats that frequently surface after a 6RA70 + UPS installation is commissioned:

• Harmonic current back into the UPS. A 6RA70 is a 6-pulse rectifier and draws 5th, 7th, 11th, 13th harmonic currents. Most double-conversion UPS units can absorb this, but the input transformer of the UPS can overheat if the drive is more than 50% of the UPS load and there is no harmonic filter. Verify UPS input transformer thermal margin in the NXA documentation.
• UPS static-bypass backfeed. If the drive regenerates and the UPS goes to static bypass, the regen energy can backfeed the bypass source. The Emerson/Vertiv NXA has backfeed protection; verify the drive's regen path does not defeat it.
• Battery DC bus ride-through. A double-conversion UPS rectifies AC to a DC bus and inverts back. During a mains event, the battery discharges into that DC bus. The drive's load on the inverter creates a step-load transient at the moment of mains loss; a 6RA70 drawing 200 kVA is a hard load for the inverter. The NXA's inverter step-load capability is the parameter to verify with Vertiv.
• Drive firmware versions and F006 behavior. The exact undervoltage threshold and the way the firmware interprets P086 can change between 6RA70 firmware builds. Always read the firmware release notes for the version on the CU and cross-check F006 behavior against the matching section of the operating instructions.
• Replacing a SIMOREG with SINAMICS DCM. For a greenfield install today, the Siemens successor is the SINAMICS DCM. The same ride-through logic applies (line-failure detection, ride-through time, restart coordination), but the parameter numbers are different. New installations should use SINAMICS DCM; this 6RA70 reference is for the installed base.

References for the Engineer

To verify the parameters, fault codes, and automatic restart logic for the exact firmware build on the user's 6RA7085-6DV62-0, refer to the SIMOREG DC MASTER 6RA70 operating instructions, Chapter 9.17 (Automatic Restart), and the parameter list for P086 and P361. The full document set is available through Siemens Industry Online Support by searching for 6RA70. The Emerson/Vertiv NXA installation and sizing manual is available through Vertiv's support portal.

Frequently Asked Questions