Three-Phase Motors; Lightning Protection - Grundfos MS Serie Instrucciones De Instalación Y Funcionamiento

5.2.2 Three-phase motors

MS motors are available with or without a built-in
temperature transmitter.
Motors with a built-in and operational temperature
transmitter must be protected by:
• a motor-protective circuit breaker with thermal
relay or
• an MP 204 motor protection unit and
contactor(s).
Motors with or without a non-operational temperature
transmitter must be protected by:
• a motor-protective circuit breaker with thermal
relay or
• an MP 204 motor protection unit and
contactor(s).
MMS motors have no built-in temperature
transmitter. A Pt100 sensor is available as an
accessory.
Motors with a Pt100 sensor must be protected by:
• a motor-protective circuit breaker with thermal
relay or
• an MP 204 motor protection unit and
contactor(s).
Motors without a Pt100 sensor must be protected by:
• a motor-protective circuit breaker with thermal
relay with max. trip class 10 according to
IEC 60947-4-1 or
• an MP 204 motor protection unit and
contactor(s).
5.2.3 Required settings of the motor-protective
circuit breaker
For motors with an MP 204 motor protection unit,
Grundfos recommends using a special trip curve with
P-characteristics at a setting of U
1 second.
For cold motors, the tripping time for the motor-
protective circuit breaker must be less than
10 seconds at five times the rated maximum current
of the motor.
For all Grundfos submersible MMS motors, the
maximum start and stop ramp time is 3 sec.
(minimum 30 Hz).
If this requirement is not met, the motor
Caution
warranty will be invalidated.
12
In order to ensure optimum protection of the
submersible motor, set the motor-protective circuit
breaker in accordance with the following guidelines:
1. Set the overload to the rated maximum current of
2. Start the motor and let it run for half an hour at
3. Slowly grade down the scale indicator until the
4. Increase the overload setting by 5 %.
The highest permissible setting is the rated
maximum current of the motor.
For motors wound for star-delta starting, set the
motor-protective circuit breaker as above, but the
maximum setting must be rated maximum current
x 0.58.
The highest permissible startup time for star-delta
starting or autotransformer starting is 2 seconds.

5.3 Lightning protection

The installation can be fitted with a special
overvoltage protection device to protect the motor
from voltage surges in the power supply lines if
lightning strikes somewhere in the area. See fig. 7.
PE
times 5 for
n
The overvoltage protection device will not, however,
protect the motor against a direct stroke of lightning.
Connect the overvoltage protection device to the
installation as close as possible to the motor and
always in accordance with local regulations.
Ask Grundfos for lightning protection devices.
MS 402 submersible motors, however, require no
further lightning protection as they are highly
insulated.
Ask for a special cable termination kit with a built-in
overvoltage protection device for Grundfos 4"
submersible motors (product no. 799911/799912).
the motor.
normal performance.
motor trip point is reached.
L1
L2
L3
825045
Three-phase
Fig. 7 Connecting an overvoltage protection
device
L
N
PE
825017
Single-phase