YASKAWA CDMR-Z II User manual

INDUSTRIAL
USE THYRISTOR
CONVERTER UNIT
Varispeed-505 ZI1
Drive
INSTRUCTIONS
MODEL
CDMR-ZII
Before
initial operation, read
these instructions thoroughly, and retain for future reference .
YASKAWA

TOE-S505-30B

IMPORTANT
When properly installed,
operated and maintained,
this equipment
will
provide a lifetime of optimum
operation . It is mandatory
that
the
person who operates, inspects,
and maintains this equipment
thoroughly read
and understand this
manual .
.
Make
no withstand voltage test on the
VS-505ZII
because it incorporates
semi-conductor electronic
circuits .
If megger tests are necessary, makethem
only
in accordance
with the instructions given in this
manual .
. Do not tamper
with potentiometers of the
power
units since
they were pre-set at
the factory be-
fore shipment
.
Type CDMR-ZII
(Type S)
230V, 105A
681-50
RECEIVING /2

Terminal Sizes
and
STORAGE
/2

Carrying
Currents / 2
Location
/ 2

Interconnections /
2
INSTALLATION
/ 2
WIRING / 2
Component
Arrangement
Cautionswhen
Wiring / 2
TEST
RUN / 4
in
VS-505Z II / 2

Check
before Test Run / 4
Type
CDMR-ZII
(Type
M)
230V, 260A
CONTENTS
Varispeed-505ZII
(VS-505ZII) is a thyristor con-
verter unit for varispeed
non-reversing operation
of
industrial DC motors .
For correct operation of VS-505ZII,
users must
throughly
read these instructions . This manual
is also necessary
for maintenance and trouble-
shooting, and therefore
should be kept field
for
ready
reference .
For
details on DC motors, refer to "Instruc-
tions for Industrial DC
Motors" (TOE-C435-3) .
Type CDMR-ZII
(Type L1
230V, 550A
No-LoadOperation / 5

Parts Replacement / 9
Full-LoadOperation / 5

Cautions
in Replacing
ControlCircuit Board / 12
Adjustment / 6
Troubleshooting Guide
/13
MAINTENANCE / 9

SPAREPARTS / 14
Periodic Inspection / 9

REFERENCE / 14

RECEIVING
The
equipment has been put through severe
tests
at the factory before shipped .

After un-
packing,
however, check and see the following .
" Its nameplate data meets
your
requirements .
" It has sustained no damage while in transit .
" Fastening bolts and screws are not loosened .
" Devices built in the cabinet are not damaged
or missing .
STORAGE
If the equipment is temporarily stored or machine
stops for
an
extended length
of time, the following
precautions should
be taken .
LOCATION
Store the equipment under
the following condi-
tions .
" Free from rainfall and drops of water
" Clean anddry
" Free from corrosive
gas and liquid
" Ambient temperature : -10 0 C to 400
C
"
Less vibration
INSTALLATION
Select
a
location described in
STORAGE and in-
stall the equipment by proper procedure in keep-
ing the equipment in good working condition .
WIRING
Make connections in
reference to the interconnection
diagram furnished on your order and
the follow-
ing .
COMPONENT
ARRANGEMENT IN
VS-505Z11
Figs . 2 to 4 show component
arrangement in the
VS-505Z]l
TERMINAL SIZES AND CARRYING
CURRENTS
Table 1 shows the size and the current carrying
capacities of the terminals
of VS-505ZII . Select
leads with sufficient
current carrying capacity .
Refer to Cautibns
when Wiring .
Table
1 Terminal Size and Current Capacity
Note :
1 .'l'erminal size other than listed
above is M4 and
current
capacity is 2A or below .
2,l1ule of thumb
of AC main circuit power capacity
12 x/ X E x 1 (VA)
E : Supply voltage
is AC main circuit current
INTERCONNECTIONS
Make connections of
VS-505ZII
with
associate
units
according
to
the interconnection diagram
separately furnished .
CAUTIONS WHEN WIRING
Main Circuits
Use 600 V
PVC
insulated wires or
cabtyre cables
with the current carrying capacities of
the
com-
bined DC motor for AC main circuit
terminals
(U, V, W) and DC main circuit terminals (P, 1) .
Field Circuits
Use 600 V PVC insulated wires or cabtyre cables
with the current carrying capacities of the com-
bined DC motor for field power circuit terminals
(Uo .
Wo .
U1,
W1)
and field circuit terminals (J,
K) . Use stranded wires of
cross-section 5 .5 mmz
or larger for field
circuit terminals (J,
K) .
Signal Circuits
Use
shielded wires or twisted wires of twisting
pitches 20
mm or
smaller for the
speed setting
circuit
terminals (11 to 16), speed feedback ter-
minals (3 to 5),
tachometer circuit
terminals (38
to 40) .
D
-_
Fig . 1

Pitch of Twisted Wire

I

20 MM
MAX .
AC
Main DC Main Field
C Dh1R-Z11
Circuit Circuit Circuit
Rated Rated
Car- Car-
I
Car-
Volt- Out-
Ter
-
rying
Ter-
rying Ter- rying
minal Cur- minal Cur- minal Cur-
age put
Size rent Size rent Size rent
V
kW
A
A A
25 M6 21 M5
25
35
M6
_
29 _M8
i
~_ - 35-
45 M6 ` 37M8 45 104 i 1-'
90 M8 74 M8 90
230
105 M 8_ 86 M8 105 -
180 M10 147 M10 180
22
260 M10 213 M10 260
M4
420 M12 343
-
M12 420
M4 25
550 M12
-
449 M12 550
50 M8 41 M8 50
90
M8 74
M8 90
M4 12
105 M8 86 M8 105 I
460 180
M10 147 M10 180
260 M10 213
M10
260
M4 22
420 M12 343 M12 _, 420
M4
'
25
550 M12 449 N112 I 550

OCL RESET
PUSHBUT-
TON
EXTERNAL
CONTROL
TERMINALS
(53)
FUSE BLOWN
DETECTION
CONNECTOR
OCL RESET
PUSHBUT-
TON
EXTERNAL
CONTROL
TERMINALS
( 53)
FUSE BLOWN
DETECTION
CONNECTOR
(a) Control Circuit

(b) Power Circuit
Fig . 2

Type CDMR-ZII, -5 (230V,
150A)
POWER
CIRCUIT
BOARD
(2PCB)
CONNECTOR
FAILURE
INDICATING
LIGHTS (6)
(a) Control Circuit

(b)
Power Circuit
Fig . 3 Type CDMR-ZII,
-M (230V, 260A)
(a) Control
Circuit

(b) Power Circuit
Fig . 4 Type CDMR-Z11, -L (230V, 550A)
TIIYRISTOR
PROTECTIVE
FUSE
(2 FOR 220 V
CLASS, 3 FOR
MAIN CIRCUIT
'

440 V CLASS)
EXTERNAL
TERMINAL
POWER
CIRCUIT

THYRISTOR
BOARD

COOLING
CONTROL
(2PCB)

FAN
CIRCUIT
BOARD
(IPCB)
CONNECTOR

WIRING
(Cont'd)
Separation
of Signal Cables from main
Circuit Cables
To avoid
inductive interference
from other cables,
run the
shielded or twistedwires (1
to 53)
separatefrom main
circuit cables (U,
V, W : U0,
W
O ;
U1,
W1 ; P
, N ;
J, K) in a bundle or thru
a
duct .
CAUTION
After wiring,
check interconnections .
Make insulation resistance
tests using
a 500V megger . Connect
VS-505ZII
main
circuit terminals ( U , V, W ; Uo,
Wo ; U 1,
W
1 ;
P,
N ; J, K) with common
lead . Measure the
insulation resist-
ance between common lead and
the
ground .
When the test result is 2 MSS
or more,
it means that wiring is
successful .
TESTRU N
When the VS-505ZII
has been correctly installed
and wired, the unit shall
be tested through a
test
run as follows .
If trouble
is found during the test run, re-
fer to "Check
Before Test Run" and "Trouble-
shooting Guide" for necessary
measures . If the
cause of the trouble cannot be
located, or repair
is
impossible, notify our service station,
giving
the details
of trouble conditions .
CHECK BEFORE
TEST RUN
Make the
following checks prior
to the test run .
Table 2 Check
before Test Run
*VS-505ZII of
larger capacity
than 230V . 45A or 460V, 90A
are provided
with a thyristor
cooling fan .
Fig . 5 Inspection Window of DC
Motor
Either 230V or 460V
at 105A or
below
When suply
voltage is
200 or 4E

V , plug
the
housing in
the upper tap .
2(KAI
1(RIV~
~n1G
~-_ _n
141
VL___J
When supply voltage is
220 or 4 V, plug the
housing in the lower tap .
AKA P-_ -
_ i l
-A
L__-J
v
44uV
When supp ly
voltage is
200 or 400
V, plug the
housing in
the left tap .
r - ?
;HRIV 20%
4(KIV 1111\
When supply voltage is
220 or 440 V, plug
the
housing in the right tap .
r - ~
~lRl
yw
UKn 11W
Fig . 6 Tap Selection of
Control Supply Voltage
Fig . 7 Selection of Supply
Frequency
Tabl,e 3 Supply
VoltageAllowable
Range
681-200
" When supply frequency is
50Hz, slide the switch
key down .
" When :supply frequency
is 60Hz, slide the switch
key up .
Check Points
Check Items
Interconnec-
"
Correct
wiring .
tions
between " Tightening of terminal screws .
VS-505ZII
and Associ-
ate Units
DC Motor " Disconnection
from the driven machine .
" Removal of thrust
block .
" Remove inspection
covers and blow out
with air to clean commutato
r . (Fig . 5)
VS-505ZII
" Adhesion of dirt or dust on
the enclosure .
"
Smooth hand rotation of
thyristor cooling
fan .*
" Check
items in "Cautions in
Operation" on
the back
of the control board door .
" Correct
connection of the shunt
connector
to the
voltage selecting tap . (Fig . 6)
"
Corrent setting of the frequency
selector
switch .
(Fig
.
7)
" Correct
adjustment of potentiometers on
the control board
UPCB) Refer to red paint
.
Supply Volt- "
Voltages of
anytwo
of
phases U, V, W are
age at Input
within the values on Table
3 . Check with
Terminals of a
tester .
VS-505ZII "
Terminal
Uo
and U1 and
Wu
nd
Ware
connected
.
"
Rotating direction of the motor blower
meets
with the arrow marked on the blower
Nominal
Supply
Permissible
Voltage
Supply
Frequency
Voltage Selectoer
V oltage Variation Tap
220 V 50/60 Hz 170 - 220 V 200 V
220 V 50/60 Hz
187 - 242 V
220 V
400 V 50/60 Hz 340 - 440 V 400 V
440 V 50/60 Hz
374 - 484 V
440 V

NO-LOAD OPERATION
After making the checks
specified before
test run,
thoroughly check the environment to the system
for safety .
Check the polarity of DC tachometer gener-
atorfeedback voltage . When the motor is run-
ning forward, the polarity of VS-505ZII signal
terminal 3 (4 : OV) is minus and it is plus during
reverse running of the motor .
Then, run the motorwithout load according
to Table 4 .
Table 4 No-load Operation
Before starting full-load operation, stop the
power supply, couple the DC motor to the driven
machine, and check the motor and the driven ma-
chine for safe and obstruction-free conditions .
Table 5 gives full-loadoperation procedure .
Table 5 Full-load Operation
*VS-505ZII, rated230V,
45A and above and 460V, 90A and above are provided with
a thyristor
cooling fan .
O r
de
r Operation
l Set the speed at zero .
2 Turn on the main circuit power supply .
3 Turn on
increase
that the
correctly
operation signal and gradually
the speed . Check to be sure
motor and driven machine are
running
.
4 Turn off the operation signal .
5
Turn off main circuit power supply .
Order operation Check Items
1 Set t h e speed re f e rence at zero . -
2 Turn on main circuit power supply . I
Smooth rotation of the thyristorcooling fan .*
i
Smooth rotation of the blower for DC motor .
Rotating direction of the blower meets with the marking
on the blow er .
3 Make an operational sequence
and check
to be sure that
operation is ready . -
(Turn on ready signal,
motor cooling fan
ON /OFF
signal .)
4
Tur n-on the oper ati o n sig nal . I -
5 Gradually, increase
the speed setting Smooth acceleration of DC motor .
value .
No abnormal odor, smoke,
vibration and noise on DC
mot or .
(, Remove the hand-hole cover and check
No brush chattering and sparking at the brushes .
tht- commutator .
To avoid excessive temperature rise of DC
motor winding in frame 112, 132, reclose the
window within 5 minutes .
7
Gradually, turn the speed setting poten-
Smooth acceleration of DC motor .
tiometer cl o ckwise .
8 Increase the speed setting value to
the DC motor rotates at the maximum speed . Check with
maximum .
a speedometer .
9 Change the speed
to various values . Turning speed setting potentiometer rapidly
during
acceleration or deceleration changes motor speed
smoothly .
10
Turn off
the
operation signal . DC motor stops . (It stops suddenly by VS-505ZII with
a dynamic b ra k ing function .)
11
Turn off the main circuit powe r supp ly . I -

TEST
RUN (cont'd)
Adjuster locations on the control circuit board
ADJUSTMENT

and functions are shown in Fig . 8 and Table 7 .
Do not
tamper unnecessarily with the
potentiom-

The characteristics of control circuit board check
eters on the
control circuit board since they have

terminalsare shown in
Fig
.
9
and Table 6 .
been adjusted at the factory
before shipped .
®Ltn
®L
® `® r®
80
'0
JPDC-C036
O
0
Adjuster
Locations and
Functions
0
Cllt1C
l17
Clll

0
CH 6 0116 \~ CH 9

Cll 1
C1110
C112
C li 3
CH 14
-1/_C11
1 .' .
' ~ C H 13
V GB
/ 11116
C1 a J1'1)C-C03i .~11
0

:-1111 7

0
(a) Type JPDC-C035

(b) Type JPDC-C036

(a) Type JPDC-C035

(b) Type JPDC-C036
Fig . 8 Adjuster Locations on

Fig . 9 Control Circuit Board
Control Circuit Board

Check Terminals
Table 6
Control
Circuit Board Check Terminals
I / Cl14
-w
0
O
JPDC-C036
CHn CHI4
CHIP, ... ~\
OHIO
cxu
ees"~I,/ G8
all ~ e 0
CHI6
CHI7
CHII\~
a
0
Signal Names
Check
NormalValues
Terminals
Phase shifter
Approx
. +5 . 5 V at 60 Hz, +1 to +5 .5V at 60Hz,
input
C H4H4
+6.5 V
at 50
Hz +1
to +6 .5
V
at 50 Hz
when gate blocked when controlling
Current
limit
CH5
+3 V/100% current limit
Speed
feedback CH6 -6 V/100% speed
Current command CH7 -3 V/100% command
L Speed command CH8 +6 V /100% command
d
c
e . Gate
block
CH9 (Gateblock by OCL)OV normal, -24V at gateblock
GB 0 V normal, +12 V at
gateblock
L
U
Current control-
CH10 Approx . -1 V at gateblock
0 to +6 V when
c
ler output
controlling
.
eo
g
Current feedback
CH11 +3
V/100%
current
Stable power
CH12 0 V
(SG)
supply
CH13 +15 V
CH14 -15 V
CH 15 +24 V
Allowable
variation
Unstable power
supply
CH16
-24 V range : f20%
CH17
+24 V (pulse amplifier
power supply)
Current command
CHI Voltage value according -6 V/5 A
Ex .
c
Current feedback CH2
to field current .
+3
V /5 A
.
p
Phase shifter
Approx . +5 V at 60 Hz, +1 to +5
V at 60 Hz,
a1 input
CH3 approx . +6 V at 50 Hz +1 to +6 V at 50 Hz
u .
when field blocked
when controlling

Table 7
Control Circuit Board Adjuster Locations
and Functions
Note : The adjusters of the circled numbers are provided
with the control circuit board
Type JPDC-C036 (ET000491X) only .
Type
of AdjusterAdjuster
'
Adjuster Functions Adjusting Method Specifications
Adjusters Location Names
1 ACCEL
Acceleration time adjustment
. i
Clockwise rotation
increases a(Celeration 3 - 75 sec
I
i time .
2 DECEh
Deceleration
time " adjustrne " nl . Clcic
kwis, rotation
ine i-ease " 5 doce " le " r .itinn
3 75 sec
_-
3 GAIN
ASR G .rrrr .i d juslm e" nl . CIoc .kwi- rotation
increases g .iin . -
4 NMAX Speed feedback adjustrru " nt Clockwise " rotation clecrvases ~peed . -6/100% speed
5 LIMIT Currant limitalu m Clockwise rotation increases limit - __0 _- _250%
value . 0 - 125%
S peed l imitation
6 IFB Main circuit current feedbackClockwise rotation decreases
current
. +3V/100%
adjustment . current
Potentio- 7
SM Speedomete r adjustment .
Cloc kw ise rotation increasespointer swing .1
mADC max
meters
8 AM Am meter a djust ment .
- - -
Clockwis e rotatio
n decreases pointer swing .
1 mADC max
9 BIAS ASR offset adjustment . e VOILELge r~ (H) voltage -
10
KIPP
Phase shift lag limit adjust-
Clockwise rotation advances shift lag . 155°el
ment (Standard)
11 OL%
Setting
overload
detection Clockwise rotation increases overload 110%
start point . detection start po int . (Standard)
12 OLT Setting overload . Clockwise rotation increasesoperation 150% . 60 sec
time . (Standard)
13 I REF Setting field current Clockwise rotation inc reases t he curr ent . -
22 PSB
Phase shifter operating point
Clockwise rotation advances phase . Adjustable
adjustment b,-t%% een
90
and
160°el
14 1FBR- Rough adjustment of field
Potentio-
4FBR current detectionvoltage
meters
level .
Open the resistor according to speci(5-
Refer to motor
selection
(Open)
15 SFBR-
Rough
adjustment
of main
cations . specifications .
SFBR circuit detection voltage
level .
Slide switch
16 1SW Supply frequency selector . Selection of 50 Hz or 60 Hz . -
©3 ACTG/
Selection
of ACTG and DCTG For AC tack-gen, select ACTG, and for
DCTG according to
Type of TG . DC tack-gen,
select DCTG .
-
17 A - D Rough adjustment of speed Selection of the voltage level according to
detection voltage level . type of lath-gen and motor rated speed .
-
18 E Selection of soft start oper- El - -
ation
E2 Sof t start -
® F Selection of BIAS
Fl
AS
R BIAS A
djustment -
__ F2 1AC R BI AS Adjus tmen -
H Selection of LIMIT 111 Curr ant limitation -
112 Spied limitation -
19 J Selection of start interlock
J
1
Possible -
zero-speed
condition
JZ
_-_"-"--- ---'-
Plug
_-
selection
20
K Selection of motor stopping Kl Gale
block
at
zero speed when -
method
decelerating to stop .
K2 Gate block at stop command . -
© L Selection of use of exciter
Ll Exc iter used . -
according to motor field .
L2 _
Exciter not used . -
©
M Selection
of field block due MI Field blocked . -
to motor overheat .
M2
Fie
ld
not
blocked . -
21 N
Selection of zero-speed N
1
Field half-reduced after motor
condition at motor cooling zero-speeds by stop operation .
-
fan
stopping .
_
2
'F'ie d a
l -r
edu ce "_
= tc_
.)oc -
28 P Selection of Pl and P of ACR PI PI control
_-
control
P 2 P c
ontr ol -
29
01-IN -
Open
"Speed control by voltage detection . -
Short-
" Speed control by AC tac h-g c" n .
circuit
Shoat
_
-----
Exc ept for
the abov
--
-
jumper
30 OP
_
Olxn Spec ial application
Short E~capt for the above -

TEST RUN
(cont'd)
AdjustmentProcedure
NMAX (Speed feedback adjustment)
To adjust the DC motorspeed exactly to the
reference speed, proceed as follows .
1 . Prepare the tachometer having
required
accuracy .
2 . Operate the DC motor at no load (or
less
variation) .
3 . Measure
the speed reference voltage with a
voltmeter . Correct the
voltage to that of
desired motor speed .
4 . Measure the motor speed
with a tachometer .
5 . If the speed
does not reach the desired
speed, turn
NMAX counterclockwise to increase
the speed .
6 . If speed
exceeds the desired speed, turn
NMAX
clockwise to decrease the speed .
LIMIT (Limit
value
adjustment)
1 .
Current limitation (Speed control)
Connect the plug-connectors F and H
to
F 1 and
Ell on the control circuit board, respectively .
When the voltage at
CH 5 is
+3V,
100 ° % current
limit value is
obtained . Current limit value can
be set within the range of 0% to 250% by LIMIT .
2 . Speed limitation (Current control)
Connect
the plug-connectors F and H to F2 and
H 2 on the
control circuit board, respectively .
When the voltage at CH 5 is +6V, 100% current
limit value is obtained . Current limit
value can
be set within the range
of 0% to 125% by LIMIT .
PSB
(Phase shifter operating point
adjustment)
PSB sets the phase shifter operating
point .
1 .
When the current controller (ACR) is inte-
gral-controlled
Connect
the plug selector P on the control circuit
board at P1 . Turn PSB fully
counterclockwise .
2 . When
the current controller (ACR) is ratio-
controlled
Connect the plug selector P on the control board
at P2 . Turn PSB clockwise gradually with ref-
erence current at OV (OV at CH 10) , and set
at
the position where main circuit current
is ready
to start .
Adjustment of Field Current
The manner of adjusting field current when
field current is constant differs from that when
field
weakening control is made .
Constant Field Current
1 .

Connect DC ammeter to field circuit .
2 .

Adjust the potentiometers
(1FBR
to
4FBR)
and IREF on the control circuit
board
so that
ammeter indicates rated field current .
Field Weakening Control
Proceed
as follows to adjust field current in
combination with field adjuster type JGSM-51-'-_',
1 . Connect DC
ammeter to field circuit and
DC
voltmeter to output terminals ® and
4 .
Set the minimum field weakening current
using I REF . Set-value should be 80% field
weakening ; current at maximum speed .
6 . Increase speed referencegradually after
motor starts .
681-13
Firs . 10 Field Adjuster Type JGSM-51-L'
2 .

Select the
potentiometer (from 1FBR to 4FBR )
which corresponds to the desiredvoltage
level
of field current
detection . Remove those poten-
tiometersnot
being used .
3 . Turn the potentiometer ]REF on the control
board and' FORCE FLD and V LIMIT of the field
adjuster fully
counterclockwise .
5 . Setthe
rated field current (field intensifying)
using
FORCE FLD of field adjuster .
The voltage
across terminals ® and O increases
as speed rises and
reaches the limited value .
Turn V LIMIT clockwisegradually so that the
limited value is motor rated voltage (220V
or
440V) .

MAINTENANCE
VS-505Z11requires
almost no daily
inspection .
To keep the correct
and successful
operation,
periodic
maintenance
operations should
be per-
formed
. The usersshould
prepare their
own
maintenance programs
based on
the following
guidelines .
PERIODIC
INSPECTION
Table
8 shows the
minimum inspection
items and
the
procedures .
PARTS REPLACEMENT
Field Thyristor
With all the Models, thyristor modules
consisting
of a thyristor and a diode are
used as the field
thyristor . Replace them
as follows .
The
same replacement procedure applies to
all themodels .
1 . Loosen the bus bar
screwsand the lead clamp-
ing
screws, and unclamp the leads . In this case .
mark all the terminals for identification . (Fig .
11)
2 . Loosen the twoclamping screws,
andremove
the thyristor module .
3 . Check thereplacement
thyristor module for
type and
capacity, and install it by reversing
the
removal procedure, making connections to
the terminals
identified by the marks
made before
removing the old thyristor module .
Table 8 Periodic Inspection
Fig . 1 1
Field Thyristor (230V,
25A)
Main Circuit
Thyristor
230V, 25A System (Fig . 12)
The system uses a thyristor module
comprising
two thyristors . Replace
it as follows .
1 .
Remove the 6 bus bar clamping screws,
and
remove the bus bar .
2 . Loosen all the thyristor
lead screws,and U11-
clamp all the leads . In this
case, mark the termi-
nals for identification
.
3 . Remove the two thyristor clamping
scre%ks .
4 . Check the replacement
thyristor module for
type and capacity,
and reinstall it by reversing
the disassembly
procedure, identifying the
terminals by means of the marks made prior
to
disassembling .
NOTE
When installing the
thyristor module,
apply thermal
compound JOINTAL Z
(made by
Nippon Light Metal Co .,
Ltd .)
to the thyristor mounting
surface (reverse side) .
Fig . 12
Main Circuit Thyristor
Fig . 13 Bus
Bar Removal
Inspection
Item
Inspection
Item
Inspection
Procedure
What to do
Thyristor
" Noise " Check for any
Replace .
cooling intermittent or Rule of
thumb
fan
unusual noise . for cooling fan
"
Vibration " Feel by hand .
replacement :
15,000 hours
of operation .
General " Dust or " Check for
dust " Clean with
dirt .
clogging or an electrical
dirt adhesion .
cleaner .
"
Check for " Tighten .
loosening of
screws
or nuts :