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Maintenance and service guide - LSPX-FLSPX ZONE
21 - Ex tb – LSES-FLSES ZONE
22 - Ex tc
5725 en - 2020.02 / c
CONSEQUENCES OF POWER SUPPLIED BY DRIVES
When power is supplied to the motor by a variable speed drive
with diode rectifier, this causes a voltage drop (~5%).
Some PWM techniques can be used to limit this voltage drop
(~2%), to the detriment of the machine temperature rise
(injection of harmonics of orders 5 and 7).
The non-sinusoidal signal (PWM) provided by the drive
generates voltage peaks at the winding terminals due to the
significant voltage variations relating to switching of the IGBTs
(also called dV/dt). Repeated overvoltages can eventually
damage the windings depending on their value and/or the
motor design.
The value of the voltage peaks is proportional to the supply
voltage.
This value can exceed the limit voltage for the windings which
is related to the wire grade, the impregnation type and the
insulation that may or may not be present in the slot bottoms or
between phases.
Another reason for attaining high voltage values is when
regeneration phenomena occur in the case of a driving load,
hence the need to prioritise freewheel stops or stops that follow
the longest permissible ramp.
7.1.2 - Minimum recommendations
The specific instructions given in the specific instruction
manuals must be followed if a drive is used. In particular the
following minimum requirements must be observed:
- Check that the drive switching frequency is 3 kHz minimum.
- Check that the motor has a second nameplate which give the
maximum characteristics and performance levels of the motor
during its use at variable speed.
- The reference voltage, usually 400V 50 Hz, is given on the
motor nameplate. The drive must deliver a constant voltage/
frequency ratio.
- Programme the maximum current value as well as the min
and max frequency values shown on the second nameplate of
the motor into the drive.
- Connect all the temperature sensors present on the motor
(windings and, if relevant, bearing housings) to safety devices
which are independent of those used for operation under
normal conditions.
Drives and sensor connection components
must
be located outside hazardous zones (zones 0, 1, 2,
20, 21 and 22).
7.1.3 - Special conditions for safe use
- As standard the motors’ impact resistance corresponds to
“low” mechanical risk, therefore they must be installed in a low
mechanical risk environment.
- The motor must be equipped with 3 thermal sensors (1 per
phase) placed in or on the stator connection side winding
heads (all frame sizes) and on the front bearing housing (from
frame size 355) in the following cases:
- motor supplied by frequency inverter
- motor in a sufficient, non self-ventilated airflow (IC418)
- motor adapted to no longer be self-ventilated (IC410)
- motor equipped with a backstop
- motor equipped with an auxiliary fan (IC416A) or radial
fan (IC416R)
The thermal protection devices must be connected
to a device which de-energises the motor when the
setting value is reached and before the maximum surface
temperature T° of the motor reaches the classification
temperature shown on the nameplate.
- When the motor is equipped with auxiliary or forced ventilation
(IC416) a device must prevent the main motor form operating
in the absence of ventilation. Stopping the auxiliary motor must
cause the main motor to stop.
- Heaters must only be supplied when there is no supply to the
motor and the latter is cold. Their use is recommended for
ambient temperatures of less than -20°C.
- Supply voltages and frequencies must comply with those
stated on the motor nameplate.
- The frequency range stated on the motor nameplate must be
strictly observed.
- In the event of several motors being supplied by the same
drive, for safety reasons individual protection must be provided
on each motor outlet (e.g. thermal relay).
- The specific instructions given in the specific instruction
manuals must be followed if a drive is used.
- Cable glands and components must be compatible with the
protection mode used for the connection portion. Alternatively,
with integral cables, the motor connection must be made
outside the explosive atmosphere or in a housing protected by
a recognised protection method which is suitable for this use.
- The degree of protection of the motor, of its main connection
housing and of any auxiliary connection box(es) is:
* for zone 21: IP65 - IK08
* for zone 22: IP55 - IK08
The user must provide additional protection if there is a high
risk.
- Variable speed
The use of these motors with a frequency or voltage inverter
supply requires specific precautions for use:
The reference voltage (inverter output or
motor input) is 400 V at 50 Hz; the drive must supply
a constant voltage/frequency to the motor.
The voltage and supply frequency range specified
by the motor nameplate must be rigorously
observed
.
Drives and sensor connection components
must
be located outside hazardous zones (zones 20, 21
and 22).
INSTALLATION AND MAINTENANCE - LSPX-FLSPX ZONE 21 - Ex tb – LSES-FLSES ZONE 22 - Ex tc