Motor Protection - Grundfos SP Series Installation And Operating Instructions Manual

6.2 Motor protection

6.2.1 Single-phase motors
Single-phase MS 402 motors incorporate a thermal switch and
require no additional motor protection.
kW (1.5 hp) MS 402 requires external current protection
DANGER
Electric shock
Death or serious personal injury
- Switch off the power supply before you start any
work on the product.
- Make sure that the power supply cannot be
accidentally switched on.
DANGER
Electric shock
Death or serious personal injury
- The pump must be connected to protective earth.
- Switch off the power supply before you start any
work on the product.
- Make sure that the power supply cannot be
accidentally switched on.
Single-phase MS 4000 motors must be protected. A protective
device can either be incorporated in a control box or be separate.
Franklin 4" PSC motors must be connected to a motor-protective
circuit breaker.
6.2.2 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 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).
MS motors are available with or without a built-in temperature
transmitter.
The following motors must be protected by a motor-protective
circuit breaker with thermal relay, or a MP 204 and contactor(s):
• motors with a built-in and intact temperature transmitter
• motors with or without a defective temperature transmitter
• motors with or without a Pt100 sensor.
MMS motors have no built-in temperature transmitter. The Pt100
and the Pt1000 sensor are available as an accessory.
6.2.3 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 Un times 5 for 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 seconds (minimum 30 Hz).
12
As an exception, the 1.1
.
.
For cold motors, the tripping time of the motor-protective circuit
breaker must be less than 10 seconds at 5 times the rated
maximum current of the motor. During normal operating
conditions the motor must be running at full speed in less than 3
seconds.
If this requirement is not met, the motor warranty will
be invalidated.
In order to ensure optimum motor
motor, set the motor-protective circuit breaker
the followingmust be set as follows:
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.
protection of the submersible
in accordance with