In DC drive systems, the Parker DC590 not only controls motor speed and torque but also integrates multiple monitoring and protection functions for the motor and the overall drive system.

When a DC motor experiences a fault in the Armature, Field winding, temperature sensor, or speed feedback circuit, the Parker DC590 can detect the abnormal condition and display the corresponding warning or trip message on the Drive.

However, a fault code does not necessarily mean that the Parker Drive itself is faulty. To accurately identify the root cause, it is necessary to check the Drive, wiring, SCR circuit, DC motor, and mechanical load as a complete system.

1. What Faults Can the Parker DC590 Detect in a DC Motor?

Some notable fault messages displayed by the Parker DC590 include:

The important point is that the same Drive fault can have several possible causes. Therefore, correctly identifying the fault code is only the first step in the troubleshooting process.

2. FIELD FAILED – DC Motor Field Loss Fault

FIELD FAILED is one of the faults that requires particular attention when a DC motor is not operating normally.

The field circuit generates the magnetic flux required for the DC motor to operate. If the field winding is open-circuit, the field supply is lost, the wiring is broken, or the field current does not reach the required level, the Parker DC590 can detect the loss of field and initiate a trip.

Common causes include:

• Open-circuit field winding in the motor.
• Blown field circuit fuse.
• Field supply contactor not closing.
• Broken wiring between the Drive and the motor.
• Fault in the field rectifier/SCR circuit.
• Damaged field winding or abnormal winding resistance.
• Incorrect field current settings.

Do not simply reset the Drive when FIELD FAILED occurs. The actual field current should be checked before restarting the motor.

3. FIELD OVER I – Excessive Field Current

The opposite condition is FIELD OVER I.

When the field current increases abnormally, the cause may be located anywhere along the following circuit:

Drive → Field circuit → Wiring → Motor field winding

If the field winding is shorted or there is a problem in the field circuit, the field current can increase significantly.

This fault should be investigated carefully before continuing operation because running the motor with excessive field current can cause overheating of the winding and reduce motor service life.

4. OVER I TRIP – Parker DC590 Armature Overcurrent

This is one of the faults that often makes operators immediately think:

“The DC motor has a short circuit.”

However, OVER I TRIP alone is not enough to conclude that the motor armature is damaged.

The following areas should be checked systematically:

Motor → Armature cable → Brushes/Commutator → Mechanical load → SCRs → Parker DC590

Possible causes of overcurrent include:

• Motor mechanically jammed.
• Excessive mechanical load.
• Armature short circuit.
• Poor brush contact.
• Burned or abnormal commutator.
• Armature cable or wiring problem.
• Faulty power SCR.
• Incorrect current limit settings.

Therefore, OVER I TRIP should be treated as an indication for fault isolation, not as a final conclusion that the motor has failed.

5. STALL TRIP – Motor Has Current but Does Not Rotate

This fault is particularly useful during troubleshooting.

A typical situation is:

RUN command → Parker DC590 supplies armature current → motor does not rotate or speed does not increase → Drive detects a stall condition.

Possible causes include:

• Motor mechanically jammed.
• Gearbox or transmission mechanism locked.
• Excessive mechanical load.
• Armature problem.
• Abnormal brushes or commutator.
• Incorrect speed feedback.
• Improper control parameters.

Therefore, when STALL TRIP occurs, do not check only the electrical system. The machine’s mechanical system should also be inspected.

6. THERMISTOR – DC Motor Overtemperature

If the motor is equipped with a temperature sensor connected to the Parker 590+ control system, the Drive can detect when the motor temperature becomes excessively high.

Possible causes include:

• Motor operating under excessive load.
• High armature current for an extended period.
• Motor cooling system not operating properly.
• Cooling fan failure.
• Dust accumulation reducing heat dissipation.
• Bearing or mechanical components becoming seized.
• Internal motor problems.

When THERMISTOR occurs, do not simply reset the Drive and continue operating. The root cause of the overheating should be identified first.

7. OVERSPEED – Don’t Blame the Encoder Immediately

Another important fault in DC motor systems is OVERSPEED.

When this fault appears, many people immediately check the encoder or tachogenerator.

That is reasonable, but it is not the only possibility.

For a separately excited DC motor, the following condition can occur:

Loss of Field → Reduced Magnetic Flux → Motor Speed Increases → Speed Exceeds the Limit → Parker DC590 Trips on OVERSPEED

Therefore, when an Overspeed fault occurs, the following should be checked together:

• Field current.
• Field circuit.
• Tachogenerator/Encoder.
• Feedback wiring.
• Speed-related parameters.
• Actual motor operating condition.

8. SPEED FEEDBACK – Speed Feedback Fault

The Parker DC590 requires a speed feedback signal for closed-loop speed control.

If the tachogenerator or encoder has a problem, such as:

• Loss of signal.
• Intermittent signal.
• Incorrect polarity.
• Broken feedback wiring.
• Feedback speed not matching the actual motor speed.

The Drive may detect the abnormal condition and generate a SPEED FEEDBACK related warning or trip.

This is why, when troubleshooting a DC Drive system, technicians should not only measure the armature voltage but also check the speed feedback signal.

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Troubleshooting the Parker DC590 by Three Main Areas

A practical troubleshooting method is to divide the system into three main groups.

Group 1 – Field

Check:

Parker DC590 → Field circuit → Wiring → Motor field winding

Key faults:

FIELD FAILED / FIELD OVER I

Group 2 – Armature

Check:

Parker DC590 → SCRs → Armature cable → Brushes/Commutator → Motor armature

Key faults:

OVER I TRIP / STALL TRIP / OVER VOLTS (VA)

Group 3 – Feedback

Check:

Motor → Tachogenerator/Encoder → Feedback wiring → Parker DC590

Key faults:

SPEED FEEDBACK / ENCODER FAILED / OVERSPEED

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A Drive Fault Does Not Necessarily Mean the Drive Is Faulty

This is one of the most important points when troubleshooting a DC Drive system.

For example:

FIELD FAILED

does not necessarily mean that the Parker DC590 itself is faulty.

The actual cause could be:

Open field winding in the motor → Loss of field current → Parker detects the condition → Drive displays FIELD FAILED.

Similarly:

OVER I TRIP

could be caused by:

Motor mechanically jammed → Armature current increases → Drive protection activates → OVER I TRIP.

Therefore, accurate troubleshooting requires checking the entire system:

Parker DC Drive + SCRs + Wiring + Armature + Field + Feedback + Mechanical Load

Conclusion

The Parker DC590 is equipped with multiple monitoring and protection functions to detect abnormal conditions in DC motor systems. Fault messages such as FIELD FAILED, FIELD OVER I, OVER I TRIP, STALL TRIP, THERMISTOR, OVERSPEED, and SPEED FEEDBACK provide valuable information for technicians to identify and isolate potential problems.

However, determining whether the DC motor or the Parker DC Drive is actually faulty requires a systematic inspection of each section of the system rather than relying solely on the fault code displayed on the Drive.

This is particularly important in high-power DC motor applications such as rolling mills, rewind/unwind machines, wire drawing machines, printing machines, coating lines, and other industrial production systems. Accurate troubleshooting can significantly reduce machine downtime and prevent unnecessary replacement of equipment.

Công Ty TNHH Kỹ Thuật Việt supplies genuine Parker DC Drives and provides technical support for DC motor control systems, including Parker DC590 fault diagnosis, configuration, replacement, and troubleshooting of industrial DC drive systems.

Contact us for technical consultation and a suitable solution for your DC Drive system.