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

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.