10
Installation and maintenance - Three-phase induction motors
4850 en - 2018.11 / f
ASSEMBLY
2.4 - Electrical guidelines
2.4.1 - Limiting problems caused by motor
starting
In order to protect the installation, any significant
temperature
rise in the cabling conduits must be prevented, while ensuring
that the protection devices do not interrupt starting.
Operating problems in other equipment connected to the same
supply are due to the voltage drop caused by the current
demand on starting - many times greater than the current
absorbed by the motor at full load (approximately 7).
See the LEROY-SOMER induction motors technical
catalogue).
Even though the mains supplies increasingly allow D.O.L.
starting, the current inrush must be reduced for certain
installations.
Jolt-free operation and soft starting ensure greater ease of use
and an increased lifespan for the machines being driven.
The two essential parameters for starting cage induction
motors are:
- starting torque
- starting current
The starting torque and the resistive torque determine the
starting time.
Depending on the load being driven, it may be necessary to
adapt the torque and the current to the machine starting time
and to the possibilities of the mains power supply.
The five essential modes are:
- D.O.L. starting
- Star/delta starting
- Soft starting with autotransformer
- Soft starting with resistors
- Electronic starting
The «electronic» starting modes control the voltage at the
motor terminals during the entire starting phase and enable
very soft, jolt-free starting.
2.4.2 - LEROY-SOMER «Digistart» electronic
starter
This is a multi-function electronic system with a microcontroller,
which is used with all 3-phase cage induction motors.
It provides soft starting of the motor with:
- Reduction of the starting current
- Gradual, jolt-free acceleration, achieved by controlling the
current absorbed by the motor.
After starting, the DIGISTART performs additional motor
control functions in its other operating phases: steady state
and deceleration.
- 18 to 1600 A models
- Supply: 220 to 700 V - 50/60 Hz
DIGISTART is economical to install, as a fused switch is the
only additional device needed.
Optional: Standard slide rails (conforming to standard NFC 51-105)
These steel slide rails are supplied with tension screws and the 4 nuts and bolts for fixing the motor on the slide rails, but the fixing
bolts for the slide rails are not supplied.
Motor
Type
Dimensions
Weight per pair
frame size
of slide rail
A
E
H
K
L
X
Y
Z
Ø J
of slide rails (kg)
90
G 90/8 PM
355
395
40
2.5
50
324
264
294
13
3
100, 112 and 132
G 132/10 PM
420
530
49.5
7
60
442
368
405
15
6
160 and 180
G 180/12 PM
630
686
60.5
7
75
575
475
525
19
11
200 and 225
G 225/16 PF
800
864
75
28.5
90
-
623
698
24
16
250 and 280
G 280/20 PF
1000
1072
100
35
112
-
764
864
30
36
315 and 355
G 355/24 PF
1250
1330
125
36
130
-
946
1064
30
60
H
L
Y
Z
X
A
E
K
ØJ
