DC Speed Governor Excitation Board C98043-A7014-L2 C98043A7014L2 C98O43-A7O14-L2

Siemens C98043-A7014-L2 | SIMOREG DC Drive Field Supply Board — DC Speed Excitation Control

Part Number: C98043-A7014-L2

Manufacturer: Siemens AG (Germany)

Product Type: Field Supply Board — DC Motor Excitation Control (DC Speed Excitation)

Product Family: SIMOREG DC Drive Series

Function: Controlled DC voltage supply for separately-excited DC motor field winding

Production Status: Discontinued by Manufacturer

Country of Origin: Germany

Overview

The C98043-A7014-L2 is the DC field supply (excitation) board for Siemens SIMOREG DC drive systems. This board delivers controlled direct current to the field winding of a separately-excited DC motor — establishing and regulating the magnetic flux that the motor needs to produce torque from its armature current.

Without a correctly-functioning field supply board, a separately-excited DC motor cannot be energised regardless of the armature supply's condition, and the drive will fault on field loss before attempting any armature operation.

The A7014 series of field supply boards occupies a specific position in the SIMOREG C98043 board family.

The C98043 series serves the larger power-range SIMOREG converter configurations, where the armature currents are substantial and the field supply board is designed accordingly.

The L2 suffix within the A7014 designation identifies this specific design generation, incorporating the component selections and circuit refinements appropriate to this production stage.

DC motor speed control operates on two distinct variables: armature current, which controls torque, and field current, which controls flux. Below base speed, field current is maintained at its rated value and speed is controlled through armature voltage.

Above base speed — in the field-weakening range — field current is progressively reduced to allow higher rotational speeds at reduced maximum torque. 

The C98043-A7014-L2 is the board that executes both modes of field control: maintaining full field at and below base speed, and executing controlled field reduction above base speed.

Key Specifications

Field Supply in Large DC Drive Architecture

The separately-excited DC motor has two electrically independent windings: the armature winding in the rotating part, and the field winding in the stationary frame.

The field winding is relatively low-current but high-inductance — it can take several seconds for field current to establish fully after the supply is switched on, due to the field circuit's time constant.

The C98043-A7014-L2 contains the thyristor bridge that converts the AC supply to a controlled DC output for the field winding, along with the control electronics that regulate this output.

The field current loop closes through a current transformer or shunt that measures the actual field current and feeds this measurement back to the board's regulator. The regulator adjusts the thyristor firing angle to maintain the commanded field current precisely.

This closed-loop control of field current is what makes accurate field weakening possible. As speed rises above base speed, the CUD1 controller commands a reduced field current setpoint.

The C98043-A7014-L2 smoothly reduces field current to match this setpoint, allowing the motor to accelerate further.

The board's response time and regulation accuracy directly affect how smoothly the drive transitions through the base speed point and how tightly it follows field weakening profiles.

Field Loss Protection

The most safety-critical function of the field supply board is field loss detection. If field current drops to zero or falls below the field loss threshold — due to a board failure, a field winding fault, or a field supply failure — the motor loses its magnetic flux.

An unfluxed motor connected to a live armature supply may accelerate without effective current control, potentially reaching dangerous speeds.

The C98043-A7014-L2 monitors field current continuously.

A detected field loss triggers an immediate armature trip through the drive's protection chain, removing the armature supply before a runaway condition can develop.

This protection responds faster than any software loop — it is implemented as hardware monitoring that acts independently of the main control processor.

Discontinued Status and Aftermarket

The C98043-A7014-L2 has been discontinued by Siemens. It is no longer available through Siemens' active product channels. The aftermarket — specialist DC drive repair companies holding tested spare boards — is the primary supply source.

Boards are typically supplied in refurbished, function-tested condition with warranty. When sourcing, confirm the L-variant (L2 in this case) against the installed board's label, as the L2 and L1 series may differ in circuit configuration.

FAQ

Q1: The SIMOREG drive shows fault F036 (field current regulator deviation too large) immediately at startup. The motor field winding resistance has been measured and is within spec. Could the C98043-A7014-L2 be the fault source?

With a confirmed-healthy field winding, F036 at startup points to either the field supply or its measurement circuit. Check the AC supply voltage at the C98043-A7014-L2's input terminals and confirm any field fuses are intact.

If supply and fuses are good, check the field current measurement signal at the board's output — an open or faulty measurement path produces a zero actual value reading, which the regulator interprets as maximum deviation.

If the measurement checks out, the thyristor bridge on the A7014-L2 may have a failed device producing insufficient or zero field current.

Q2: The C98043-A7014-L2 is described as a "DC speed excitation board." What does "DC speed excitation" mean in this context?

"DC speed excitation" refers to the function of providing controlled DC excitation current to a DC motor — the term "excitation" in DC motor terminology means the magnetisation of the motor's field poles.

Speed control of a DC motor depends on both armature current (torque) and field current (flux/speed).

The field supply board — the "speed excitation" board — directly participates in speed control by managing field current, particularly in the field-weakening range above base speed.

Q3: Can the C98043-A7014-L2 be replaced with the C98043-A7004-L2 (the field supply board for standard 6RA70 drives)?

No — the A7014 and A7004 series field supply boards are different products for different drive platforms. The A7004 series serves the standard SIMOREG 6RA70 drives, while the A7014 series serves larger SIMOREG converter configurations.

They differ in current rating, circuit design, and physical form factor. Always use the exact series and variant matching the installed board.

Installing a lower-rated A7004 in an A7014 position would result in undersized field current capability and potential board damage.

Q4: After replacing the C98043-A7014-L2, the field current is present but shows a slow, oscillatory response during speed changes. What should be adjusted?

Oscillatory field current response indicates a mismatch between the field current regulator gains in the CUD1 and the motor's field circuit inductance/resistance characteristics. The field circuit time constant of large DC motors can be several seconds.

If the regulator gains were not re-entered or checked against the original commissioning data after the board replacement, they may not match the motor. Access the field regulator parameters in the CUD1 and confirm they match the original values or the motor's field winding specifications.

An auto-tune sequence (if the firmware version supports it) will re-calculate the gains.

Q5: The drive is in a continuous rolling mill application where the field supply board must have maximum reliability. Is there a modern successor product that could improve reliability compared to the discontinued C98043-A7014-L2?

For installations willing to undergo drive modernisation, the SINAMICS DCM (DC Master) is Siemens' current platform for high-performance DC motor speed control. The SINAMICS DCM integrates field supply as an internal function — there is no separate field supply board to maintain.

For sites where maintaining the existing SIMOREG hardware is preferred, preventive replacement of the field supply board during a planned shutdown — before a fault in service — is the best reliability strategy, using a verified aftermarket C98043-A7014-L2 as the spare.