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

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).