Sr. No.

Notes
1) Motor starting analysis are generally performed for the largest motor connected to a
switchboard.

2) For worst case results, motor starting analysis are generally performed considering the
weakest source.

3) Considering the above two facts, any given electrical network, where a starting analysis of
a motor is required, can be reduced to a simplified network consisting of a source
(generator/s or grid), the starting motor (largest motor), the running motor/s (second
largest motor/s or motor of same rating as the largest motor under study) and other loads
lumped together.

4) Modeling
This spread sheet allows the user to model a given network as follows:
a) Generator/s: The details of one generator shall be entered. If there are more than one
generator of identical rating, these can be modeled simply by enter the number of
generator in parallel.

b) Grid: The details of grid shall be entered

c) Transformer/s: The details of one transformer shall be entered. If there are more than one
transformer of identical rating, these can be modeled simply by enter the number of
transformer in parallel.

d) The spread sheet considered either the "Generator/s" or the "Grid" supply for the motor
starting analysis. The "source for the motor starting analysis" can be selected by the
use via the drop down menu. The selection automatically simulates switching "ON" or
"OFF" the respective source breaker.

e) Starting Motor: The details of the largest motor connected to the switchboard shall be
entered.

f) Running Motor/s: The details of the second largest running motor/s (or motor of rating
same as the starting motor) connected to the switchboard shall be entered. This model can
also be utilized by the user to check the voltage drop at the terminals of any remote
motor/s.

g) Lumped Load: The details of the remaing load on the switchboard can be modeled as a
lumped load. The % motor can be defined which shall be modeled as constant power load
while remaining % of load shall be modeled as constant impedance load for the
calculation.
h) Error in data entry of the "voltage" input shall be highlighted, if bus voltages are much
different from the generator terminal voltage input of transformer voltage ratio inputs.

5) Calculation: The spread sheet performs a static motor starting analysis using the iterative
method. The re-acceleration of motors is not considered.
Ensure that the following options are enabled:
Tools=>Options=> Calculation=> Automatic=> Iteration=>Max iteration= 100=> Max
change = 0.001
Note: Change of any variable in the spread sheet, automatically initiates the iteration and
recalculated the results. It may happen that due to incorrect details, the iteration diverges
and erroneous results are displayed. In such case, check and correct the input and press
"Ctrl+Shift+H" to reset.

6) Results: Two sets are of results are displayed on the spread sheet as follows:
 Prestart: These voltages and power flows results are for "Pre-start" condition. i.e. before
the starting of the "Starting motor"
During: These voltages and power flows results are for "Starting" condition. i.e. at the time
of starting of the "Starting motor"
The voltage variations shall be highlighted if they exceed the permissible limits
Also power flow over the cable-1 shall be highlighted if it exceeds the generator capacity

7) Application: This spread sheet can be useful for following checks

a) Accessing normal running and starting voltage drops
b) Deciding the number/rating of the generator for starting a given rating of largest motor
c) Checking adequacy of selected cable sizes etc.
8) Feedback:
Please send the feedback regarding the spread sheet to hemant.kashikar@gmail.com
Your feedback is valuable and shall help me to improvise.
 Notes
Grid Fault MVA Grid Grid Grid
E= ### kV X/R Z1 R1 X1
1) The spread sheet cells highlighted as are for user
3-ph ohms ohms ohms
data entry.
100 6 12 0.36000 0.02990 0.35876
2) Following voltage variation is permissible:
Min Max
100.00
SOURCE FOR STATIC MOTOR STARTING ANALYSIS = GRID ONLY During normal operation: 95% 105%

0.817 MVar 0.488 MVar

0.842 pf
0.868 MW 0.762 MW

87.0 A
Prestart
During motor starting condition: 80% 115%

3) The static motor starting analysis allows user to select

either the generator/s or grid supply as source. (Weak

115.1

0.728
source should be considered for worst case results).

During
Set Grid 4) The spread sheet allows more than one number of
100.0%
Terminal voltage = transformer /generator / motor of identical rating to be
Vt-prestart 100.00% modeled in parallel. The load flow result indicated on the
Bus-3 Voltage = 6.000 kV branch side are for single circuit.
Vt-duringstart 99.66%
5) Voltages and power flows for "pre-start" condition, i.e.
before starting of the motor are displayed in "black" font.
Voltages and power flows for "during-start" condition, i.e.
6) at the time of starting of the motor are displayed in "blue"
4.5 0.3 font.
Transformer/s

Nos. of 7.5 0.5

Transformers = 1
in parallel X'mer X'mer X'mer X'mer X'mer X'mer
X'mer X'mer
pri sec Imp - Z1 Z1 R1 X1
MVA X/R
kV kV (pu) ohms ohms ohms

Nos. of Generator 2.5 6 0.4 0.060 10.67 0.00384 0.00036 0.00382

= 1
E= 100.0% circuits in parallel Vt-prestart 100.0%
0.060
0.3
Generator/s Vt-duringstart 99.66%
R 0.0016
0.5
G pf Xd" Xd' Xs Qmax
Set Generator MVA kV Xd"/R
100.0% (pu) (pu) (pu) (pu) Mvar
Terminal voltage =
Bus-1 Voltage = 0.400 kV 1 0.4 0.8 0.20 0.28 20 1.55 0.835 0.80

0.817 MW 0.488 MVar

0.842 pf
0.868 MW 0.762 MW

1726.4 1305.2 A
Vt-prestart 100.00% 0.20 0.0448 0.248

Prestart
Vt-duringstart 100.00%

0.728
0.000 MVar 0.000 MVar
1.000 pf

0.000 MW 0.000 MW
0.0 A

Cable-1 : size 3C185

Prestart
0.00

During
r x
Nos of length
(ohms/ (ohms/
runs (km)
km) km)
0.00

0.0

1.000

During

0.1270 0.0780 3 0.1

OFF ON
MW Mvar pf Amp
Bus-2 Voltage = 0.400 kV
Prestart 0.760 0.468 0.851 1305.2
Vt-prestart 98.68% 97.19% 98.68%
During 0.865 0.783 0.741 1726.41
Vt-duringstart 97.52% 96.35% 97.52% ON ON ON

Cable-2 : size 3C185 Cable-3 : size 3C185 Cable-4 : size 3C185

r x r x r x
Nos of length Nos of length Nos of length
(ohms/ (ohms/ (ohms/ (ohms/ (ohms/ (ohms/
0.316 MVar 0.000 MVar

0.425 MVar 0.427 MVar

0.042 MVar 0.042 MVar

0.107 MW 0.000 MW

0.691 MW 0.693 MW

0.067 MW 0.067 MW
runs (km) runs (km) runs (km)
Prestart

Prestart

Prestart
km) km) km) km) km) km)
0.1270 0.0780 1 0.1 0.1280 0.0750 1 0.15 0.1280 0.0750 2 0.15
During

During

During
Vt-prestart 98.68% Bus-4 Voltage = 0.400 kV Vt-prestart 87.22% Bus-5 Voltage = 0.400 kV Vt-prestart 98.12% Bus-6 Voltage = 0.400 kV

Vt-duringstart 95.09% pf eff LRC LRC pf Vt-duringstart 85.96% Vt-duringstart 96.96% pf eff REVISION-1
MW kV MW kV pf (pu) % Motor MW kV
M (pu) (pu) (pu) (pu) M (pu) (pu)
Nos. of Motor
= 1 Prepared By
0.045 0.4 0.75 0.75 4.5 0.3 0.65 0.4 0.85 75% circuits 0.05 0.4 0.85 0.75
Starting Running
Motor Lumped Motor/s
FLC Amp 115.47 494.14
Load
FLC Amp 1189.8 1200.2 FLC Amp 115.37 116.76 GshopNmore