FIRE PUMPS
Electric Motor Driven
8
14
10
7
11
6
12
13
9
Approved Controller Starting Methods
Type Starting
Characteristics
Across the line
Connects motor directly to power
source. Full voltage applied to motor when
controller is actuated.
Primary
Resistance
Reduced Voltage
When controller is actuated, a resistance
is connected to each phase. Resistors are
bypassed after a time delay and motor then
runs at full voltage.
Part Winding
Motor starts on one winding. After a
time delay, second winding is connected in
parallel to the line.
* Low relative cost
* Low starting torque
* Low maintenance
On controller activation, motor windings wyeconnected for starting, After a time delay,
automatically converts to delta connection
for running, applying full voltage to motor
windings. Most often used with transfer
switch/emergency generator applications.
Wye-Delta
Same sequence as Open Transition.
Closed-Transition Connected to resistors in each phase
during transition from wye to delta.
* Moderate to low
relative cost
* Low motor stress
* Low starting current
Wye-Delta
Open-Transition
Auto
Transformer
Reduced Voltage
w/50% tap
w/ 65% tap
w/80% tap
Soft Start/Stop
Starters supply reduced voltage starting
at motor terminals through use of tapped,
3-phase autotransformer. A timing relay
causes transfer of motor from reduced
voltage start to line voltage operation without
disconnecting motor from power source.
Reduces inrush current to motor with
adjustable ramp time. Stop sequence reduces
possibility of surges occurring in the system.
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Advantages
* Least expensive
* Highest starting torque
* Low maintenance
* Standard motor used
* Smooth starting
* Low shock to motor
* Standard motor used
* Moderate to high relative cost
* Low motor stress
* Low starting current
* No line transients
* Good for heavy
starting loads
* Highest starting torque
* Standard motor used
* Low starting current
* Starting torque adjustable
* Low inrush current
* Adjustable ramp time
* Reduces system surges
* Standard motor used
Restraints
* High inrush current
* High power loss through resistors
* Must dissipate heat
* Low torque per ampere input
* Medium relative cost
* Not recommended for transfer
switch applications
* Not recommended for
frequent starting
* Low starting torque
* Special motor required
* Medium starting torque
* Special motor required for
200V–208V
* Power line transients
* Can affect other equipment
sharing same power source
* Medium starting torque
* Special motor may be required
for 200V–208V
* High relative cost
* Large heavy cabinet
* Legacy technology
* High relative cost
Starting Current Starting Torque
Type
(% Motor Full Load
(% Locked
Transition
Starting Current)
Rotor Torque)
600%
100%
N/A
300%
25%
Closed
390%
42%
Closed
200%
33%
Open
200%
33%
Open
Closed
150%
252%
384%
Adjustable
50–500%
25%
42%
64%
Varies,
down to 30%
Closed
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