Motor Protection; Lightning Protection - Grundfos SP Series Installation And Operating Instructions Manual

6.1 Motor protection

6.1.1 Single-phase motors
Single-phase MS402 motors incorporate a thermal switch and
require no additional motor protection. As an exception, the 1.1 kW
(1.5 hp) MS402 requires external current protection.
DANGER
Electric shock
Death or serious personal injury
‐
Switch off the power supply before starting any work
on the product.
‐
Make sure that the power supply cannot be accidental-
ly switched on.
DANGER
Electric shock
Death or serious personal injury
‐
The pump must be connected to protective earth.
‐
Switch off the power supply before starting any work
on the product.
‐
Make sure that the power supply cannot be accidental-
ly switched on.
Single-phase MS4000 motors must be protected. A protective
device can either be incorporated in a control box or be separate.
6.1.2 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 the following:
• 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 the following:
• 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).
6.1.3 Required settings of 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 times 5 for 1 second.
n
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 seconds (minimum 30 Hz).
If this requirement is not met, the motor warranty will be
invalidated.
In order to ensure optimum protection of the submersible motor, set
the motor-protective circuit breaker in accordance with the
following:
1. Set the motor-protective circuit breaker to the rated maximum
current of the motor.
2. Start the pump and let it run for half an hour at normal
performance.
3. Slowly grade down the scale indicator until the motor trip point is
reached.
4. Increase the setting by 5 %.
The highest permissible setting is the rated maximum current of the
motor.
For motors wound for star-delta starting, the motor-protective circuit
breaker must be set 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.

6.2 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. 8
L1
L2
L3
PE
825045
1
Connecting an overvoltage protective device
Pos. Description
1 Three-phase
2 Single-phase
The overvoltage protective device will not, however, protect the
motor against a direct stroke of lightning.
Connect the overvoltage protective device to the installation as
close as possible to the motor and always in accordance with local
regulations. Ask Grundfos for lightning protective devices.
MS402 motors, however, require no further lightning protection as
they are highly insulated.
L
N
PE
825017
2
13