Type of
Starter |
Voltage
at Motor |
Line
Current |
Starting
Torque |
Advantages |
Limitations |
|
------------------------------------------------------------------------------- |
| Full Voltage |
100% |
100% |
100% |
-
Lowest cost
-
Less maintenance
-
Highest starting torque
|
- Starting inrush current may exceed limits of
electrical distribution system
- Starting torque may be too high for the application
|
|
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| Auto Transformer |
80
65
50 |
64
42
25 |
64
42
25 |
- Provides most torque per ampere of line current
- Taps on auto transformer permit adjustment of
starting voltage
- Suitable for long starting periods
- Closed transition starting
|
- In lower Hp rating, is most expensive design
- Heavy, physically largest type
- Low power factor
- Most complex of reduced voltage starters because
proper sequencing of energization must be maintained
|
|
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Primary
Resistance |
80 |
65 |
42 |
- Lease complex method to obtain reduced voltage
starting characteristics on low capacity systems because
interlocking of contactors is unnecessary
- Smoothest acceleration of electromechanical types
- Improves starting power factor because voltage
current lag is shortened by putting a resistance in series with the
motor
- Less expensive than auto transformer starter in
lower Hp ratings
|
- Additional power loss in resistors compared to
other types of starters
- Low torque efficiency (decreases as voltage is
decreased)
- Starting characteristics not easily adjusted after
manufacture
- Duty cycle may be limited by resistor rating
- High initial inrush current
|
|
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| Part Winding |
100 |
65 |
42 |
- Starter less expensive than other types of reduced
voltage control
- Closed circuit transition
- Most dual voltage motors can be started part
winding on lower of two voltages
- Control smaller than other types
|
- Torque efficiency usually poor for 3600 RPM motors
- Possibility of motor not fully accelerating due to
torque dips
- Unsuitable for high inertia, long standing loads
- Requires special motor design for voltages other
than 230V
|
|
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| Wye Delta |
100 |
33 |
33 |
- Low torque efficiency
- No torque dips or unusual winding stresses occur as
in part winding starting
|
- Requires special motor design
- Starting torque is low
- Usually not suitable for high inertia loads
- Control more complex than many other starter types
|
|
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| Solid State |
Adjust |
Adjust |
Adjust |
- Includes constant current, ramped current, or
tachometer type starting
- Adjustable current limit and starting time
- Increased duty cycle compared to electromechanical
types
- Power factor controller and line voltage limiting
included
- Multiple adjustable point over wide range
- Smoothest acceleration
|
- Specialized maintenance required
- Shorting contactor is required for NEMA 4 and 12 enclosure
- Ventilation required
- Higher priced
- Isolation contactor may be required
|
