PRECILEC RE.0444N Guide for On site Maintenance and Replacement of DC Speed Generator

Tighten the flange screws (torque reference M6 screws about 8-10 N · m).

Connect the coupling, tighten the screws, and leave an axial gap of about 1mm to prevent thermal expansion.

6.4 Electrical Connection and Polarity Verification

Connect the output line according to the original label. If the polarity of the new speedometer is opposite, two wires can be exchanged or the controller parameters can be changed.

Use a multimeter to measure the resistance range of the output terminal to the casing, which should be greater than 1M Ω. If it is too small, check whether there is an internal short circuit.

Manually rotate the motor shaft slowly (or jog), and use a DC voltmeter to measure whether the output polarity corresponds to the direction of rotation.

6.5 No load and load testing

Start the motor to the lowest stable speed (e.g. 100 rpm) and observe whether the controller speed feedback display is stable.

Gradually increase the speed to the rated value and record the corresponding relationship between the output voltage and the set speed. If the deviation exceeds 2%, the controller speed feedback gain can be adjusted.

Use an oscilloscope to monitor the output ripple. If it exceeds the standard, a 0.1 μ F~1 μ F capacitor can be temporarily connected in parallel (at the input of the controller and without causing oscillation).

After continuous operation for 1 hour, the temperature of the touch speed measuring machine casing should not exceed 80 ℃ (environment 25 ℃). If it is too high, check if it is due to excessive radial stress or poor lubrication.

6.6 Fill in maintenance records

Fill in the replacement date, new speedometer serial number, Ke value, and test data in the equipment file for future traceability.

Chapter 7 Preventive Maintenance Suggestions

To extend the service life of RE.0444N, it is recommended to perform the following maintenance every 6-12 months:

Electric brush inspection: Remove the electric brush and measure the remaining length (about 8-10mm for a new brush). If it is less than 5mm, it needs to be replaced. Check that the electric brush leads are not loose.

Cleaning of the commutator: Wipe the surface of the commutator with a cotton cloth moistened with anhydrous alcohol to remove carbon powder accumulation. If there are grooves on the surface, use 00 grit sandpaper to polish.

Bearing lubrication: For bearings without sealing covers, add special bearing grease (such as Shell Alvania RL2). For ZZ type double caps, if there is no grease injection or abnormal noise, replace them immediately.

Insulation resistance test: Use a 500V megohmmeter to measure the insulation between the winding and the casing, and record the resistance value. If it is lower than 2M Ω, it needs to be dried (dried at 80 ℃ for 12 hours).

Output signal inspection: Measure the output voltage at commonly used speed points (such as 20%, 50%, 100% of rated speed) and compare it with historical data. If there is a persistent deviation, consider demagnetization or line attenuation.

Chapter 8 Quick Q&A of Common Questions

Q1: Can RE.044N be used in situations with frequent forward and reverse rotation?

A: Okay. The polarity of the output voltage of the permanent magnet DC tachometer generator changes with the direction of rotation and can be used for four quadrant speed feedback. However, frequent commutation will accelerate the wear of the electric brush, so it is recommended to use precious metal electric brushes.

Q2: Can the output end be directly connected in parallel with a voltmeter or PLC analog input?

A: Sure, but the load impedance should be greater than 10k Ω, otherwise it will cause nonlinearity. If the PLC input is 0-10V and the output of the speedometer is higher, precision resistor voltage division is required (note that high input impedance is still required after voltage division).

Q3: What should I do if the AC component of the speedometer output is too large, causing fluctuations in the speed of the frequency converter?

A: Connect a first stage active low-pass filter (cut-off frequency 100Hz) in series before the signal line enters the frequency converter, or use an isolation transmitter (such as a signal isolator) to achieve filtering and isolation simultaneously.

Q4: Can RE.044N be replaced with an encoder?

A: In principle, the encoder provides digital pulses, while the speedometer provides analog voltage. If the control system only accepts analog signals, an encoder with an F/V module can be used as a substitute, but it is necessary to confirm whether the dynamic response meets the requirements (the speedometer time constant is 2.5ms, and the F/V may be delayed by 5-10ms).

Q5: Does the outer shell of the speedometer have induced voltage and feel numb when touched?

A: Possible poor grounding or accumulation of static electricity. Use a multimeter to measure the voltage of the casing to ground. If there is AC voltage, check if the shielding layer is grounded at both ends (single ended). The shell must be reliably grounded.