Explains about Motor parts and characteristics.

1. MOTORS

2.  To convert electrical energy into
mechanical energy in order to accelerate
the motor and load to operating speed –
Starting Function
 To convert electrical energy into productive
work output from the machine – Work
Function

3.  STATOR-The stator consists of magnetic poles
and stator windings within the frame of the motor.
By variation of winding configuration and the
contour of the stator laminations , the full load
characteristics are determined
 The motor speed is determined by the number of
poles

4.  ROTOR- The rotor consists of a cylindrical short-
circuited winding around iron laminations The
rotor design affects starting performance.
 The shape, position and material of the rotor bars
affect the current drawn and torque produced
during motor starting.

5.  Full load characteristics are well understood with
factors such as motor speed,torque and efficiency
being the typical selection criteria.
 A motor‘s start performance characteristics are
usually the least understood but set the limits of
what can be achieved with either a full voltage or
reduced voltage starter.
 It is especially important to consider motor start
characteristics when seeking to:
- Minimise start current
- Maximise start torque

7.  Starting Torque (LRT) is produced by a motor
when it is initially turned on. Starting torque is the
amount required to overcome the inertia from
standstill.
 Pull-up Torque is the minimum torque generated
by the motor as it accelerates from standstill to
operating speed. If the motor’s pull-up torque is
less than that required by its application load , the
motor will overheat and eventually stall.

9.  Current rises instantaneously to LRC levels. This
causes a current transient that can have
undesirable effects on the supply.
 Current gradually falls as motor speed increases.
 Motor loading affects only the time taken for
acceleration, not the magnitude of current which
is always LRC.

10.  Current transient
 Current magnitude
 Torque transient
 Torque magnitude
Reduced voltage starting attempts to overcome
these limitations by applying the voltage gradually.