Sedgwick SM255t, Operation And Maintenance Instructions, Page: 10 / 32

SM255t Operation/Maintenance Instructions Page 10 of 32
4.0 Electrical Installation
Electrical wiring should only be carried out by a fully qualified electrician taking
in account the following safety instructions.
• The motor, starter, and isolator have been wired in at the factory and tested before
despatch. All that is required is to connect the power supply to the isolator.
• Check that the supply details on the motor nameplate correspond with the site
supply.
• It is important that the correct cable size is used to avoid a voltage drop at the
motor terminals. If the motor is operated on a voltage outside, plus or minus 6% of
the spot voltage, then premature failure will occur.
• Do not wire single-phase machines into a 13 amp plug socket.
• It is important to check rotation of the spindle which should be anti-clockwise when
viewed from the front of the machine.
Should you encounter problems on start-up check for the following likely causes:
Symptom
Check
Machine does not start at all. Isolator is switched to ON and all STOP buttons are out.
Overload button is reset.
Starter coil/contactor is operational.
There are no loose connections.
There are no fuses blown.
Supply is reaching the starter.
Supply is reaching the motor.
Voltage between the phases at starter and motor.
Motor runs but trips. Overload setting in starter.
Current drawn without load applied.
Current drawn under load.
Supply voltage without load and on moment of switch on.
Allowed variation plus/minus 6%.
Supply voltage under load.
Supply voltage with motor off.
Supply to all three phases at isolator, starter and at motor.
Note that it is possible for 3 phase machines to operate
with only 2 phases of the supply. This is known as single
phasing. Check all fuses.
Motor attempts to start then
trips. The machine is not jammed, and the spindle is free to
rotate.
Winding resistance of each motor phase (values should all
balance).
Insulation resistance between windings and earth.
The correct cable size has been used to install the
machine (long runs of cable can cause voltage drop).