Grundfos MG, Instructions Manual

Page: 11 / 76

English (GB)
11
9. Start-up
9.1 Measuring the insulation resistance
Measure the insulation resistance before start-up and in case of
any risk of moisture in the windings.
Calculate the minimum permissible insulation resistance, R,
by multiplying the rated voltage (in kV) of the motor with the
constant 0.5 megohm/kV.
Stop using the motor immediately if the insulation resistance falls
below this value.
Example
If the rated voltage is 690 V, the measured resistance must be
higher than 0.69 kV x 0.5 megohm/kV = 0.35 megohm.
Measure the minimum permissible insulation resistance at a
winding temperature of 25 °C (+/- 15 °C).
Procedure:
• Connect the megaohmmeter between phase and earth at a
measuring voltage of 500 V DC.
• Read the value on the megaohmmeter.
If the minimum insulation resistance is not attained, the windings
are too moist and must be oven-dried.
The oven temperature must be 90 °C for 12-16 hours and then
105 °C for 6-8 hours.
9.2 Direction of rotation
The direction of rotation is clockwise, seen from the motor drive
end when the mains conductors are connected in accordance
with the diagram located in the terminal box cover. The direction
of rotation can be changed by switching two random mains
conductors.
10. Operation
10.1 Max. number of starts per hour
See page 70 .
11. Maintenance
11.1 Motor
Inspect the motor at regular intervals, determined by the
environment in which the motor is installed. To ensure adequate
ventilation, it is important to keep the motor clean. If the motor is
installed in a dusty environment, it must be cleaned and checked
more often than if it is installed in non-dusty environment.
In standard motors, condensed water cannot escape. The drain
hole at the lowest point of the motor can be opened and ensure
the escape of water entering the stator housing, for example in
connection with condensation.
11.2 Motor bearings
11.2.1 Motors without lubricating nipples
The bearings are greased for life. The expected life is at least
18000 operating hours at an ambient temperature of up to 40 °C.
A higher ambient temperature reduces life. A temperature
increase of 10 °C reduces life by 50 %.
Bearing grease
The technical specifications of the grease must correspond to
DIN 51825, K3N or better.
• 50 cSt (mm
2
/s) at 40 °C
• 8 cSt (mm
2
/s) at 100 °C.
Grease filling rate: 30-40 %.
11.2.2 Motors with lubricating nipples
Lubricate the bearings with high-temperature grease as specified
on the motor nameplate with mechanical data.
Lubricating intervals are stated on the lubricating plate for 40 °C
and 60 °C.
We recommend to dismantle the motor when the bearings have
been relubricated five times. Clean and check the bearings for
damage; replace them if necessary.
In the case of seasonal operation (motor is idle for more than six
months of the year), we recommend to lubricate the motor
bearings when you take it out of operation.
It is important to relubricate the bearings as specified on the
motor nameplate with mechanical data. If this interval is not
observed, the bearing life will be reduced.
Reduced lubricating interval
The lubricating interval must be reduced in these situations:
• Dirty and dusty environments. Reduce the lubricating interval
by a factor 0.75.
• Very moist environments. Reduce the lubricating interval by a
factor 0.9.
If the environments are both dusty and moist, multiply the factors.
Grease type and quantity
See the motor nameplate with mechanical data.
12. Technical data
12.1 Weight
See nameplate, WinCAPS or WebCAPS.
12.2 Enclosure class
See nameplate, WinCAPS or WebCAPS.
12.3 Dimensional sketches
See page 71 .
12.4 Sound pressure level
See WinCAPS or WebCAPS.
12.5 Winding resistances
See WinCAPS, WebCAPS or MG Product Information, PI-052,
section "Technical data".
Warning
When measuring the insulation resistance,
carefully follow the safety regulations of
EN 50110-1 (operation of power plants) and the
instruction manual for measuring and test
equipment.
Warning
During and immediately after the measurement,
there will be a risk of electric shock. Do not touch
the terminals until the windings are de-energised.
Note Remove any drain plugs before heating.
Caution
Some MG motors have a properly directed fan.
The direction of rotation must be as stated on the
motor.
Warning
During operation, the motor surface may be so
hot that it may cause personal injury.
Note
Never mix grease with thickeners, such as
lithium-based grease with polycarbamide-based
grease.