Code of Practice for the Electricity (Wiring) Regulations - 2009 Edition

(3) Starting facilities of electric motors
(a) The starting facilities of induction motors of various sizes should
restrict the starting current of the motors to maximum acceptable
limits as required by the electricity supplier.
(i) Low voltage induction motors
(A) The choice of motor size and maximum acceptable starting
current should be in accordance with the following table:
Supply Arrangement
From Electricity
Supplier’s Overhead
Line System
From Electricity
Supplier’s
Non-overhead Line
System
Motor Size (M) in
Kilowatts
M 1.5
1.5 M 3.8
3.8 M 11
M 2.2
2.2 M 11
11 M 55
No. of
Phases
1-phase
3-phase
3-phase
1-phase
3-phase
3-phase
Maximum Starting
Current (in Multiple of
Full Load Current)
6 .0
6 .0
2.5
(B) Motors exceeding the limits stipulated in the table above
must be approved in writing by the electricity supplier.
(ii) Synchronous motors and high voltage motors should only be
installed by special arrangement with the electricity supplier.
(b) Except where failure to start after a brief interruption would be likely
to cause greater danger, motors should be provided with means to
prevent automatic restarting after the stoppage due to drop in
voltage or failure of supply, where unexpected restarting of the
motor might cause danger. These requirements do not preclude
arrangements for starting a motor at intervals by an automatic
control device, where other adequate precautions are taken against
danger from unexpected restarting.
26D Supply Connection to Transformers
(a) Where an autotransformer is connected to a circuit having a neutral
conductor, the common terminal of the winding should be connected to
the neutral conductor.
(b) Where a step-up transformer is used, a linked switch should be provided
for disconnecting the transformer from all live conductors (i.e. phase and
neutral conductors) of the supply.
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6 .0
6 .0
2.5