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

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

In industrial speed control and regulation systems, a DC tachometer generator is a feedback component that converts mechanical speed into an analog voltage signal. It is widely used in applications that require precise speed closed-loop control, such as elevators, steel mills, CNC machine tools, and generator excitation regulation. RE.0444N (model suffix N represents standard type) is a permanent magnet DC tachometer generator produced by a European manufacturer. With its maximum speed of 12000 rpm, maximum electromotive force of 600V, and multiple mechanical/electrical options, it has become an irreplaceable feedback component in many old equipment or imported production lines.

However, as the service life of the equipment increases, the original RE.0444N may face end-of-life, performance degradation, or accidental damage. How to accurately select substitutes, install and debug on site, and diagnose typical faults (such as excessive ripples, poor linearity, and temperature drift) has become an urgent need for maintenance engineers. This article is based on the original technical specification of RE.0444N, combined with the general maintenance experience of the speed generator, systematically sorting out the key parameters, installation dimensions, wiring polarity, performance verification methods, and replacement process of this model, to help engineers quickly restore the equipment speed feedback function.

Chapter 1 RE.0444N Core Parameters and Technical Characteristics

1.1 Basic Structure

RE.0444N is a two pole (2 poles) permanent magnet DC tachometer generator, which uses Alnico permanent magnet material for excitation and does not require an external excitation power supply. The number of armature slots is 19, the number of commutator segments is 57, the insulation level is Class B (IEC 34-1), and the maximum allowable winding temperature is 130 ℃. The protection level is IP44, and if a sealing cover is selected, it can be increased to IP55, suitable for general industrial dust and drip environments. The climate protection level complies with the Ca level (moisture and heat resistance) of IEC 68-1.

Key mechanical parameters:

Net weight: 1.8 kg (single commutator type), 2.1 kg (double commutator type)

Moment of inertia: 0.95 kg · cm ²

No load driving torque: 1.5 N · cm

Time constant: 2.5 ms (fast response)

1.2 Electrical performance indicators

Parameter symbol numerical description

Maximum speed n_max 12000 rpm, short-term allowable

Maximum electromotive force E-max 600 V output upper limit

Recommended load for high impedance input with load current of 5 mA

Calibration accuracy Δ E ± 1% E factory calibration deviation

Maximum linear error Δ E ≤ 0.15% E Optimal linearity

Overall ripple rate (peak to peak value) Δ E ≤ 0.5% E commutation ripple

Slot harmonic (Z · n) Δ E ≤ 0.3% E frequency is the number of slots multiplied by the rotational speed

Rotating harmonic (2p · n) Δ E ≤ 0.2% E frequency is 2 x number of poles x speed

Electromotive force temperature drift (uncompensated) 0.02%/℃ per degree change of 0.02%

Electromotive force temperature drift (compensation) 0.005%/℃ improved by compensating winding

Analysis: The low linear error (≤ 0.15%) and low ripple rate (≤ 0.5%) of RE.0444N make it suitable for high-precision speed control. When the temperature drift is not compensated, it changes by 0.2% every 10 ℃. For a wide temperature environment, a compensation type or an external temperature compensation circuit should be selected.

1.3 Optional Filter Parameters

If a built-in or external filter is used, its time constant is 0.47 ms, which can effectively weaken the commutation ripple, but it will introduce a small phase lag. A trade-off is needed in the fast response speed loop.

Chapter 2 Detailed Explanation of Installation Forms and Dimensions

RE.0444N offers two standard mechanical installation forms: flange installation (B5) and foot installation (B3), and supports multiple shaft diameters and bearing options.

2.1 B5 flange mounting

The flange is installed by fitting the front circular flange to the motor or machine end face and fixing it with bolts. Suitable for coaxial direct connection with the dragging motor.

Key installation dimensions (unit: mm):

Shaft diameter (D) 1 commutator A 2 commutator A 1 commutator B 2 commutator B 1 commutator C 2 commutator C

Ø7 mm 126 142 132 148 14.5 30.0

Ø11 mm 131 —— 137 —— 17.5 ——

Ø14 mm 128 —— 141 —— 21.5 ——

A: The length from the flange end face to the first commutator installation face

B: The length from the flange end face to the installation surface of the second commutator (if any)

C: The length of the commutator itself (axial direction)

Note: The dual commutator model (2 commutators) only offers Ø 7 mm shaft diameter, and the two commutators are arranged axially, increasing the total length.

2.2 B3 Base mounting

The foot installation is fixed on the substrate through four mounting holes at the bottom of the machine base, suitable for independent installation or connection through a coupling.

Typical appearance: The height from the surface of the foot to the axis meets IEC standards. Please refer to the original factory drawings for specific dimensions (detailed data is not provided in the PDF, but can be confirmed by measuring the actual object).

2.3 Shaft Extension and Bearing Options

The standard configuration adopts 7x22x7 ZZ double-sided dust-proof cover deep groove ball bearings (corresponding dimensions: inner diameter 7mm, outer diameter 22mm, width 7mm). According to user requirements, special shaft diameters (up to 14mm) and larger bearings (such as 11x28x8 ZZ or 15x32x9 ZZ) can be provided. When used in situations beyond clutch or heavy load, reinforced bearings should be selected and the radial allowable stress should be confirmed.

Shaft diameter (D) Standard bearings Special bearings (optional) Allow radial stress (F)

7 mm 7x22x7 ZZ-0.4 daN (7x30mm axis length)

11 mm —— 11x28x8 ZZ 1.0 daN (11x30mm)

14 mm —— 15x32x9 ZZ ——

Radial stress warning: Exceeding the allowable value can result in shortened bearing life or shaft bending, leading to abnormal output waveform.

Chapter 3 Electrical Connections and Polarity Determination

3.1 Standard wiring (single commutator type)

RE.0444N adopts color lead output:

Red: Positive polarity (+)

White: Negative polarity (-)

Polarity definition (when viewed counterclockwise from the axis extension end): red positive white negative. If the rotation direction is changed to clockwise, the polarity of the output voltage will be reversed.

3.2 Dual commutator type (2 independent output channels)

The dual commutator model provides two independent speed measurement outputs, suitable for redundant feedback or simultaneous driving of two controllers:

First commutator: blue (+), white (-)

Second commutator: yellow (+), green (-)

The two outputs are electrically isolated but share the same permanent magnet magnetic field. When a short circuit occurs on one side, the other side can still work (attention should be paid to magnetic field interference).

3.3 Shielding and Grounding

The output of the speed generator is a low-level analog signal (up to 600V at full scale, but commonly ranging from 0 to 10V or 0 to 100V). To reduce noise:

Use twisted pair shielded cables (such as Belden 8761).

The shielding layer is grounded at a single point on the receiving end (controller side).

Avoid laying power lines in the same conduit as communication power lines.

Chapter 4 Typical Fault Diagnosis and Troubleshooting

4.1 Fault phenomenon: Abnormal low output voltage or no output

Possible reasons:

Demagnetization of permanent magnets (commonly found in high temperature or severe vibration environments).

Electric brush wear or sticking (oxidation on the surface of the commutator).

Winding open circuit (overcurrent burning or solder joint detachment).

The coupling slips (the actual speed is zero).

Diagnostic steps:

Manual turning, measure the output terminal with a multimeter in DC voltage range, and there should be millivolt level voltage generated. If it is 0V, check the brush grip pressure and the surface of the commutator.

Measure the insulation of the winding to ground with a 500V megohmmeter (normal ≥ 10M Ω). If it is low, it may be affected by moisture or breakdown.

If the insulation is normal but there is no output, remove the electric brush and measure the resistance between the commutator segments with a resistance meter. Normal should be continuous and uniform (several ohms to tens of ohms). If something is infinitely large, it is a broken line.

Check the magnetic field strength: Measure the air gap magnetic density with a Gaussian meter and compare it with the factory value (usually 0.2~0.4T). If the demagnetization exceeds 20%, it is recommended to replace it as a whole.

4.2 Fault phenomenon: The output voltage ripple is too large (>0.5% peak value), and the speed display jumps

Possible reasons:

The surface of the commutator is rough and the mica groove protrudes.

Uneven contact pressure of the electric brush or mismatched material of the electric brush.

The load current exceeds 5mA (output impedance is too low).

The controller input has not been filtered.

Exclusion method:

Use an oscilloscope to observe the output waveform and identify the ripple frequency: if it is the commutation frequency (approximately speed x number of commutator segments/60), it is a problem with the commutator itself. Polish the surface of the commutator with fine sandpaper and clean the mica grooves between the plates.

Check the load resistance: Disconnect the controller input, connect a 10k Ω~100k Ω load, and then check if the ripple decreases significantly. If it decreases, the internal resistance of the original load is too low (<2k Ω), and a voltage follower needs to be added.

External RC low-pass filter (e.g. R=1k Ω, C=0.47μF， The time constant of 0.47ms can effectively suppress high-frequency ripple. But note that it may slightly decrease the response.

4.3 Fault phenomenon: Nonlinear output voltage and speed (especially at low speeds)

Possible reasons:

The contact resistance of the electric brush is non-linear (especially below 100 rpm).

Hysteresis effect or remanence effect.

The coupling is not concentric, causing the shaft to twist.

diagnosis:

Drive the speedometer with a standard speed source (such as a calibrated motor) and measure the output voltage at different speeds. Draw an E/n curve, which should theoretically be a zero crossing straight line. If the low-speed section is significantly bent, the reason is due to the voltage drop caused by the contact of the electric brush. Low noise electric brushes (including silver graphite) can be replaced.

Check the concentricity of the shaft: Install the speedometer separately and measure the shaft runout with a dial gauge, which should be less than 0.05mm. Otherwise, it needs to be realigned.

4.4 Fault phenomenon: Output decrease after temperature rise

Reason: The negative temperature coefficient of permanent magnet materials (aluminum nickel cobalt is about -0.02%/℃). The uncompensated type has an output variation of 0.8% at a temperature difference of 40 ℃, which is unacceptable for precision systems.

Solution:

Select compensation model (provided by the original factory with Δ E ≤ 0.005%/℃). Compensate the winding in series with a thermistor or utilize an additional magnetic shunt.

Perform temperature compensation in the controller software: install PT100 temperature measurement and modify the gain coefficient.

Or replace it with a higher grade rare earth permanent magnet tachometer generator (but pay attention to the external dimensions).

4.5 Fault phenomenon: abnormal bearing noise or shaft jamming

Reason: The bearing grease has dried up, worn out, or foreign objects have entered.

handle:

Remove the speedometer and manually rotate the shaft smoothly without any jamming. If it gets stuck, try cleaning the bearings and adding low-temperature grease (such as Kluber NBU15) first.

If it still fails, replace the bearing with the same specification (such as 7x22x7 ZZ). Pay attention to protecting the commutator and winding during disassembly.

Chapter 5 RE.0444N Replacement Selection Guide after Discontinuation

When the original RE.0444N cannot be purchased, an alternative tachometer generator can be determined by the following steps:

5.1 Record key parameters

Obtain from nameplate or manual:

Voltage constant (Ke): Unit V/krpm (RE.0444N is not directly given, but can be calculated from rated speed and voltage). For example, if the output is 60V at 1000 rpm, then Ke=60V/krpm.

Maximum speed: 12000 rpm.

Maximum output voltage: 600V (but only needs to cover the voltage corresponding to the highest system speed in practice).

Installation dimensions: shaft diameter, flange or foot hole spacing.

Number of commutators: single or double.

5.2 Finding direct alternatives

Priority should be given to subsequent models of the same brand (such as RE.0444N which may be replaced by RE.0444N2 or RE.0444L). Other European brands (such as Siemens 1KV, Leine&Linde, AVTRON) with compatible size models can also be selected. Need to verify:

Axis extension size and flange installation hole.

Output polarity (whether it matches the original controller, otherwise signal conditioning is required).

Temperature drift level (compensated/uncompensated).

5.3 Transformation and replacement (when the size does not match)

If you cannot find a directly compatible mechanical size, you can:

A universal speedometer installed with a foot and a self-made transition flange.

Adopting a split type speedometer: sensor (encoder)+analog conversion module. For example, using an incremental encoder in conjunction with an F/V converter to output 0-10V, but attention should be paid to response time.

In special circumstances, keep the speedometer casing and only replace the internal armature components (provided by the repair shop).

5.4 Verification testing after replacement

After the installation of the new speed measuring machine, the following verifications must be carried out:

Polarity check: Drive at low speed and confirm that the feedback voltage polarity is correct for the speed loop polarity (positive feedback can cause runaway).

Linearity test: Use a standard speed source or compare it with another known speedometer, record the voltage at 5 speed points, and calculate the nonlinear error.

Ripple test: Measure with an oscilloscope to ensure that the ripple rate meets the original system requirements (generally<1%).

Temperature rise test: After running continuously for 2 hours, measure the output voltage drift, which should be within the allowable range.

Chapter 6 On site Replacement Operation Process (Taking B5 Flange Installation as an Example)

Assuming that the original RE.0444N is damaged and needs to be replaced with a new part (of the same model or substitute):

6.1 Preparation work

Power off: Turn off the power to the drive and control system, and hang the lock indicator.

Tools: Allen wrench, socket (M4~M6), wheel puller, torque wrench, multimeter, oscilloscope.

Record the original wiring: Take photos to record the color and terminal number of the leads.

6.2 Disassembling the old speedometer

Remove the junction box cover from the speedometer casing and remove the output leads (clearly marked).

Loosen the fastening screws of the coupling between the speedometer and the motor. Use a wheel puller to pull the speedometer out of the motor shaft end, avoiding hitting the shaft end.

Remove the 4 mounting screws from the flange and remove the old speedometer.

6.3 Installing a new speedometer

Clean the motor shaft end and flange joint surface, and apply a thin layer of rust proof oil.

Install the coupling half onto the new speedometer shaft, paying attention to aligning the keyway.

Align the flange of the new tachometer with the end face of the motor, pre tighten the screws, and adjust the coaxiality (check the radial runout with a dial indicator<0.1mm).

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.