Why Siemens 6SE7023-2ES87-2DA1 Trips During Deceleration: Six Field Checks
2026-11-06
Why Siemens 6SE7023-2ES87-2DA1 Trips During Deceleration: Six Field Checks
Siemens braking-unit troubleshooting
Why faults appear during deceleration or regenerative loading
Siemens 6SE7023-2ES87-2DA1 may operate normally at steady speed yet show DC-link overvoltage, resistor overheating or a braking fault during fast or repeated stops. These symptoms point to a problem in how regenerative energy or heat is handled, but they do not prove the braking unit itself has failed.
Start with six field checks: event pattern, resistor identity, cabling, cooling, protection signals and braking duty. Use P3, P20 and PDB only after the operating conditions have been recorded.
The short answerRecord whether the event follows fast deceleration, an overhauling load or repeated stops. If F006 appears on the connected drive, verify the supply and complete braking path before replacing the unit.
DC-link behavior
Why the fault often appears during regenerative stops
Siemens 6SE7023-2ES87-2DA1 is a SIMOVERT MASTERDRIVES braking unit for a problem that appears whenever a driven machine returns energy to the drive. During deceleration, an overhauling load or a high-inertia rotor can drive the motor as a generator. The returned energy raises the DC-link voltage.
The braking unit monitors that DC link. When its response level is reached, the chopper transfers pulses of energy to the external resistor. The resistor then converts electrical energy into heat, limiting the rise in DC-link voltage.
Regenerative-energy path. During deceleration, returned motor energy raises the DC-link voltage; the braking unit diverts that energy to the external resistor, where it becomes heat.
Motor and loadMechanical energy returns during deceleration or overhauling operation.
→
Drive DC linkReturned energy pushes the DC-link voltage upward.
→
6SE7023-2ES87-2DA1The braking chopper switches energy into the resistor circuit.
→
Braking resistorElectrical energy becomes heat and must be safely dissipated.
Field sequence
Six checks before blaming the braking unit
Use the symptom and the installed hardware together. The aim is to identify where returned energy or heat stops being handled correctly—not to replace diagnosis with one fault code.
1
Confirm the event patternRecord whether the fault appears during fast deceleration, lowering load or repeated stops. If the connected drive reports F006, Siemens identifies it as DC-link overvoltage; also verify supply voltage and phase condition.
2
Verify the braking resistorConfirm 6SE7023-2ES87-2DC0, 20 Ω, thermal-contact wiring and any visible heat damage. Do not judge the resistor from appearance alone.
3
Inspect the cable pathCheck twisted DC-link conductors, a drive-to-unit length no longer than 3 m, a resistor cable shorter than 15 m, and tight undamaged terminals.
4
Check airflow and heatVerify at least 100 mm around ventilation slots, enclosure airflow, ambient temperature and nearby heat sources. Record discoloration or repeated overtemperature.
5
Test the protection chainCheck the braking-unit fault or overtemperature output, the resistor’s normally closed thermal contact and the resulting main-contactor action.
6
Compare duty with capacityRecord deceleration time and cycle interval. P3 and P20 describe short events; repeated or long braking must be judged against the 5 kW continuous PDB limit.
Important: an F006 message does not by itself prove that 6SE7023-2ES87-2DA1 has failed. The operating condition, supply, resistor circuit, cabling, cooling and protection signals must be checked together.
Quick answer
What P3, P20 and PDB actually mean
Siemens defines these figures on a 90-second duty-cycle basis. Use them only after the operating pattern has been recorded.
Duty value
Published power
Meaning during troubleshooting
P3
30 kW
Brief peak profile: full peak for 3 seconds, followed by a linear reduction over 20 seconds.
P20
20 kW
Available for 20 seconds within the 90-second cycle; not a continuous rating.
PDB
5 kW
Continuous limit; the key figure when braking lasts longer or repeats with little cooling time.
Documentation basis: the 20 kW P20, 30 kW P3 and 5 kW PDB values above are published in the Siemens application table on its stated 774 V DC response-threshold basis. The applicable unit instructions, nameplate and switch configuration remain authoritative during service.
Published hardware
The exact braking-unit and resistor record
Record
Published value
Why it matters
Braking unit
6SE7023-2ES87-2DA1
Exact SIMOVERT MASTERDRIVES order number.
DC input
510–650 V DC
Shown in the operating instructions for this exact unit.
Assigned resistor
6SE7023-2ES87-2DC0
Published Siemens braking-resistor assignment.
Resistance
20 Ω
The resistance belongs to the assigned resistor record.
Fusing
2 × 3NE4102
Application-table requirement associated with the configuration.
Product identity
Read the hardware and nameplate together
Complete unit. Confirm the SIMOVERT MASTERDRIVES construction and full order number before service. Click to enlarge.Connection side. Record terminal condition, cable routing and ventilation before the fault evidence is disturbed.
Order number6SE7023-2ES87-2DA1
Published DC input510–650 V DC
Record in serviceThreshold marking and switch position
Read the complete nameplate: threshold markings in the unit documentation may differ from the basis used in a separate application table. Commissioning and repairs should follow the instructions applicable to the installed hardware.
Installation boundaries
Cable length and heat explain many repeated faults
≤ 3 mTwist the DC-link connecting cables and keep the drive-to-braking-unit connection no longer than 3 m.
< 15 mKeep the cable from the braking unit to the external resistor shorter than 15 m.
≥ 100 mmMaintain at least 100 mm clearance around ventilation slots according to the operating instructions.
IP20The braking unit and assigned resistor are open equipment; enclosure and site conditions must respect the published protection class.
Hot surfaces are normal but hazardous. Siemens warns that braking-unit exit air can exceed 80 °C, the housing surface can exceed 65 °C, and the resistor surface can reach several hundred degrees Celsius. Keep combustible material and explosive gases away, provide airflow, and mount the resistor on a nonflammable surface.
Protective monitoring
Use both fault and overtemperature signals
The braking-unit signal output changes state if the unit detects a fault or excessive temperature. The external resistor also provides a normally closed overtemperature contact that opens when it overheats. Siemens describes integrating these signals so the drive is isolated from the line through the main contactor when a braking fault or resistor overtemperature occurs.
Braking-unit statusFault / overtemperature output
+
Resistor thermal contactNormally closed; opens hot
→
Protective shutdownMain contactor isolates the drive
Special case
Check the storage history only when it applies
More than one year without operation
Siemens states that the DC-link capacitors in the braking unit must be formed after more than one year of non-operation. Record the storage or shutdown date so this requirement is not missed during recommissioning.
Do not switch onto a live DC link
The instructions warn against connecting the braking unit to a charged DC link through a contactor. The DC-link connection procedure belongs in the controlled isolation and commissioning plan.
This is safety-relevant power-electronics work. Qualified personnel should use the applicable Siemens operating instructions, verify that the DC link is discharged and follow the site’s lockout procedure.
Quick FAQ
Common 6SE7023-2ES87-2DA1 questions
Why can the fault appear only during deceleration or an overhauling load?
During regenerative operation, the motor returns energy to the drive and raises the DC-link voltage. The braking unit must transfer that energy to the external resistor. A problem in energy dissipation, cooling or the protection chain may therefore appear only in these operating conditions.
What does F006 mean on a connected SIMOVERT MASTERDRIVES drive?
Siemens defines F006 as DC-link overvoltage. Record whether it occurs during deceleration, but also check the supply voltage and phase condition before concluding that the braking unit itself is faulty.
Which resistor is assigned to the unit?
The Siemens application note assigns braking resistor 6SE7023-2ES87-2DC0, rated at 20 ohms. The stated resistor dimensions are 485 × 485 × 305 mm and its mass is approximately 17 kg.
How long can the DC-link and resistor cables be?
Siemens states that the DC-link connection should be twisted and no longer than 3 m. The braking-unit-to-resistor cable should be shorter than 15 m.
Why can a braking resistor overheat even when the peak power looks adequate?
Peak power covers a short event; temperature is driven by energy over time and the interval between events. A high braking frequency can exceed continuous or cyclic thermal capacity even when each individual peak remains below P3.
Which protection signals should be checked?
Check the braking-unit fault or overtemperature output, the normally closed thermal contact on the external resistor, and the resulting main-contactor action. Siemens describes using these signals to isolate the drive when a braking fault or resistor overtemperature occurs.
Which rating matters during frequent or long braking events?
The continuous PDB value is the relevant limit when braking lasts longer or cycles repeat with little cooling time. For this unit, Siemens publishes 5 kW PDB; the 20 kW P20 and 30 kW P3 figures describe shorter events.
What should be checked after more than one year out of service?
Siemens says the braking unit’s DC-link capacitors must be formed after more than one year without operation. This work should follow the applicable Siemens instructions and be performed by qualified personnel.
Documentation
Technical sources
Siemens application note — MM440 with MASTERDRIVES braking unitSiemens document ID 22093967 · Version 4.2
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