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TB166 Rev3 Encoder Alignment on AC Brushless Motors
Purpose
AC drives rely on knowing the motor position in order to stay synchronized while driving the motor Before the motor is
mounted on a machine the motors encoder commutation tracks are aligned with the motor phases The drive applies
sinusoidal voltages to the three phase input to rotate the motor shaft to a starting position Typically there will be four poles in a full
rotation of the shaft In Centroid software t he index pulse can be aligned with any one of these
The drive also looks at the commutation lines from the encoder to give it a coarse position of the shaft for smooth movement
on power up These commutation signals are interpreted by the drive as zones 1 through 6 As the motor turns clockwise looking at the
output shaft the encoder counts should increase Centroid AC motors use a differential 8 pole 5V quadrature encoder with an index
pulse The encoder resolution depends on the motor and the drive see below
This procedure can also be repeated if you suspect the encoder alignment is incorrect An incorrect alignment will show
the following symptoms
1 Axis is jumping
2 Motor is running roughly
3 Motor runs better in one direction than the other
4 Motor has an uneven amount of current draw in one direction than the other
5 Large current draw with a light load
Prerequisites
Γ’Β’ If connecting a motor to a drive for the first time please completed the following steps
Γ’Β¦ Check for >100 M ΓΒ© between the motor chassis and power terminals
Γ’Β¦ With the motor connected to drive confirm continuity between the drive chassis and motor chassis
Γ’Β¦ On the drive terminal check for > 100 M ΓΒ© between your power and shield terminals
Γ’Β¦ Check VM wiring for correct polarity
Γ’Β¦ Additional information on motor testing can be found in your installation manual and Technical Bulletin 155
Tools and Equipment for Encoder Alignment
Γ’Β¦ A set of metric and SAE hex keys
Γ’Β¦ A small Philips head screw driver set
Γ’Β¦ Loctite Blue 242 Optional
Γ’Β’ If removing the motor from the machine a set of clamps such as Irwin Quick Grips
Γ’Β¦ If there is any contamination or debris inside the end cap basic cleaning supplies such as a paper towel and all purpose
cleaner
Γ’Β’ If changing the encoder the correct replacement encoder and pigtail see chart on next page
TB166 Rev3 Encoder Alignment on AC Brushless Motors
Stock Centroid AC Encoders
Encoder Model Encoder Description Typical Application Encoder Pigtail 2
Quantum Devices
QR12 2048 8 A B E A A 2 048 line 8 pole 5V
8mm shaft 750W 1KW and 2KW motors in systems not using
an AC/DC drive For 1KW and larger motors
Drawing Number S13244
For 750W motors
Drawing Number S13267Quantum Devices
QR12 10000 8 A B E A A 10 000 line 8 poles 5V
8mm shaft Motors used with the AC/DC drive
Dynapar
F144096/8395A 4 096 line 8 pole 5V
8mm shaft 3kW and 4KW motors in systems not using an
AC/DC drive Drawing Number S14427
OBSOLETE 1
Koyo
TRDA VC2048v8 7154
2 048 line 8 pole 5V
8mm shaft 750W 1KW and 2KW motors in older systems No drawings available online
Contact Centroid for details OBSOLETE 1
Dynapar
F142048/8395A
OBSOLETE 1
Renco
R35i 2048/8
1 Obsolete Encoders Obsolete encoders are replaced by Quantum Devices Model QR12 2048 8 A B E A A If you are replacing an obsolete encoder with a Quantum
encoder you may need to drill and tap new encoder mounting holes
2 Encoder Pigtails Drawings are for standard pigtails using standard Centroid motors T hese drawing might not apply to some rotary tables retrofits/upgrades or custom
systems
Older motors may have a temperature sensor on the motor connected to pins S & T of the MS connector Disconnect the temperature sensor by unplugging it if
possible or cutting the wires Use of the motor temperature sensor was never supported and newer encoder cables and pigtails use pin T as the shield ground At the
bottom of Figure 5 you can see an example of a cut temperature sensor
If you are replacing the encoder pigtail inspect the condition of the rubber gasket around the MS connector Worn gaskets need to be replaced A replacement gasket is
Centroid Part Number 4647
TB166 Rev3 Encoder Alignment on AC Brushless Motors
Alignment Setup
The motor must be disconnected from the machine or have the machine drive belt removed for the alignment process This
procedure is best performed on a sturdy bench where you have good lighting and easy access to the encoder If the motor is removed
from the machine the motor frame must be firmly secured to the bench using clamps or some other attachment method The motor
may try to jump around during the procedure especially if something goes wrong during the alignment Before starting the alignment
procedure the drive software must be configured correctly
Alignment Procedure
DANGER Do not jog the axis until instructed!
1 Remove the motor end cap
1 NOTICE Any dust dirt coolant or other contamination inside the motor end cap can get inside the sensitive
internal components of the optical encoder and cause a premature failure Make sure the inside of the motor
end cap and encoder mounting plate are clean before continuing with encoder alignment
If there is a large amount of contamination inside the end cap there is a high probability that the existing
encoder will work unreliably and need to be replaced If there is liquid inside the end cap there may also be
liquid inside the motor A motor with liquid inside is a serious safety hazard and will have to be replaced
2 If installing a new encoder remove the old encoder Attach the new encoder Loosely tighten the encoder ears
and encoder set screws so the encoder spins when the shaft moves TIP A small nylon washer between the
encoder mounting screws and the encoder ears will make alignment easier This step is optional
3 Connect power cable and encoder cable from the drive to the motor
4 Power up your drive and control system running Centroid CNC software
5 In your CNC software access the PID menu by pressing F1 Setup F3 Config F4 PID as shown below in
Figure 1 Homing the motor is not necessary
6 L ooking at the motor mounting flange manually rotate the motor shaft clockwise The Γ’absolute positionΓ’ on the
PID screen should increase as circled in the picture above If the position does not increase check the drive
communication encoder cable and encoder pigtail Figure 2 Drive Configuration Menu
TB166 Rev3 Encoder Alignment on AC Brushless Motors
1 NOTICE The AC/DC drive needs the encoder correctly connected/wired before starting up the CNC11
software or drive If the encoder is not detected upon start up you will need to restart both the AC/DC drive
and the CNC11 software before trying to test the encoder again AC/DC users can troubleshoot drive errors
through the HSC bit screen definitions as described in the AC/DC manual
7 Go to the drive configuration menu by pressing F8 Drive as shown below in Figure 2
8 Press F2 Move Sync as circled in Figure 2 The axis selected is shown underneath PWM Kp as circled in Figure
3 If you are not on the correct axis press F1 Toggle Axis until the correct axis label is on the screen Finally
press F10 GO The shaft should rotate The first move sync rotation may cause the motor to jerk or move
roughly Move sync a few more times by pressing F2 Move Sync then F10 GO repeatedly All move syncs after
the first sync should cause the shaft to rotate smoothly If the motor oscillates wildly moves erratically or
makes loud unusual noises kill the motor power immediately!
1 DANGER An incorrectly wired or configured motor may move violently or unpredictably when attempting
move sync Keep your body and others away from the motor when move syncing for the first time and be
prepared to hit the emergency stop
2 DANGER Large motors may have a tendency to oscillate violently during a move sync due to nature of the
current feedback loop It is recommended for 3KW and larger motors that you adjust the motor current to half
of the recommended value in the current feedback menu while move syncing After the encoder alignment
process is complete set the current back to the recommended setting
3 NOTICE If the motor slightly oscillates after move syncing or continues to move a little rough while move
syncing grab the motor on the shaft carefully with your hand Move sync the motor while gently squeezing
the motor shaft If the oscillations and/or jerky movements go away after applying a small amount of load to
the shaft this is normal This problem will not occur during normal motor operation
4 NOTICE If no motor movement occurs an error was encountered AC/DC users can troubleshoot drive errors
through the HSC bit screen definitions as described in the AC/DC manual Figure 3 Move Sync
Figure 2 Drive Configuration Menu
TB166 Rev3 Encoder Alignment on AC Brushless Motors
9 Keep running the move sync operation until the point where the encoder reading is closest to 0 or its maximum
encoder count The Γ’Encoder ReadingΓ’ is circled in Figure 4
10 Loosen the encoder collar set screws as shown in Figure 5
11 Move the encoder until the encoder reading is as close to zero as reasonably possible
12 Tighten the encoder collar set screws The encoder collar usually has two set screws on most encoders; make
sure both are tight if applicable
13 Loosen up the encoder ears and use them to fine tune the adjustment When the encoder is within specifications
a red message will appear on the control saying Γ’*** Tighten Encoder Now *** Γ’ as circled in Figure 4 Tighten
the encoder ears The encoder mounting plate is usually made out of aluminum so DO NOT OVERTIGHTEN! If
the screws do not fit tightly in the encoder mounting plate Loctite blue 242 or similar may be used
14 Press F2 Move Sync and F10 Go to rotate the motor shaft several full revolutions Verify that the software still
displays Γ’*** Tighten Encoder Now ***Γ’ when closest to the zero position Some encoder re adjustment may be
needed Observe the commutation count goes 1 through 6 consecutively The commutation count is displayed
below encoder reading as circled in Figure 4 At rest position the commutation zone should be either a 1 or a 6
only A 0 or a 7 as the commutation value indicates a bad encoder or wiring problem
15 Install the end cap onto the motor Be careful placing the encoder cable in the end cap If the cable is causing
any strain or tension on the encoder it will push the encoder out of alignment
16 Reboot the drive and control system Figure 4 Encoder Alignment
Figure 5 Encoder Collar Set Screws
TB166 Rev3 Encoder Alignment on AC Brushless Motors
17 After a reboot fast jog the motor in each direction to verify correct operation
18 In the drive configuration menu do a final move sync check to verify that the motor is still aligned correctly Look
for the red message saying Γ’*** Tighten Encoder Now *** Γ’ when the motor is closest to zero
19 The motor is ready for normal operation after the system has been rebooted again
Important Notice!
This procedure must be done every time a new encoder is installed on a Centroid AC Brushless motor
Document History
Rev3 Created on 2014 03 10 by #369
Rev2 Created on 2012 05 16 by #240
Rev1 Created on 2004 06 10 by #240