1. Electric Motor Drive Systems
Stewart Prince
Electric Motor Drive Systems
DN4K 35
By
2. 1
Terms of Reference Stuart Logan has instructed Stewart Prince to
produce a report on Electric Drive Systems, and to include
appropriate recommendations. The report was required for
submission on November 2014.
Procedure
This project was discussed and agreed with the
teacher/lecturer.
Various books and papers from the library were analysed.
Information was obtained from several different websites.
The load conditions that the motor will operate in are:-
Maximum Load - 11kW
Speed -1480rpm
Ambient temperature -60oC
Supply Voltage - 400V
Supply Frequency -50Hz
Location -Internal
3. 2
Contents
Section 1 Selected motor
Section 2 Transmission system
Section 3 Electrical protection
Section 4 Starting and braking arrangements
Section 5 conclusion
Section 6 appendix
4. 3
Section 1
Selected motor
Manufacturer ABB
Output
Kw
Motor
type
Produc
t code
Spee
d
R/min
Eff on
full
load
100%
¾ of
load
75%
Power
factor
cos ϕ at
100%
Curren
t In
A
Curren
t Is
In
A
Torque
Tn
Nm
11 M3BP
V 160
M
3GBP
162
501-
••E
1460 90.7 91.5 0.84 21 7.2 71
So I have chosen totally enclosed squirrel cage 3 phase motor, this
type of motor is suitable for high ambient temperatures, these
motors are good at maintaining a constant output power. Another
consideration is the heat the motor will produce, so this is why I
have decided to go for a motor that can handle 90oC ambient
temperature.
Three phase squirrel cage motors are used in industry due to them
being rugged, very dependable and the running cost of them is very
low and therefore in the current economic climate is a must,
especially in industry applications.
These motors can been used as a fixed speed motor but advances
in technology has resulted in variable frequency drives , this allows
us to slow or to speed these motors up if we require them to do so.
These motor require to be taken out of duty every 3400 hours to be
greased so at this interval I would have them maintained, it would
be necessary to have another motor ready so that the centrifugal-
fan attached to this motor to continue to run.
5. 4
Section 2
Transmission system
They are several different ways to transmit power these include
Pulley drives
Clutches
Motor drive gearboxes
Chain and sprocket
All of these systems will link motor drives to the mechanical load,
this depends on several factors these factors include
Distance to the load
What torque is required to drive the load
Environmental conditions
So I need to look at the load, I have a centrifugal fan which requires
a constant torque so this rules out any belt driven system due to
when the belt is attached and turned on it will start to slacken off
and therefore it can cause a lowering of torque and therefore can’t
be used.
Next one clutches again due to how close my motor will be to the
load this is again not possible to use.
Next system is motor drive gearbox again this is not suitable for my
load due to how close my motor sits beside the load.
The sprocket and chain is the link system for my load, this will give
a constant torque that goes to my load ensuring that it will
continuously run and not lose any torque.
6. 5
Section 3
Electrical protection MCB
Type D MCB rated at 25A
Merlin Gerin C60HD type D (10 - 14In)
This mcb is for protection against short circuits and overloads,
especially useful against high inrush of current during the motor
start-up and is good for electric motors. It will trip in 0.1 seconds if
overcurrent or a short circuit is detected, so the motor will stop and
will not be damaged.
Fuse
When selecting a suitable fuse we must take into consideration the
full load current of 21 amps which I found on the manufacturers
website for the selected motor, as I could not find a 21 amp motor
rated fuse I had to look for a 25amp fuse, I selected one from
Bussman by Eaton which is suitable (see appendix for technical
data) even though is rated 4 amps above the rated, if I had chosen
a 20 amp fuse this would not be suitable.
7. 6
Section 4
Starting and braking arrangements
Again there are several methods of starting an electrical motor
these include:
Variable speed drives
Variable frequency drives
Star delta starting
Direct On Line
The main benefits in using variable frequency drives or variable
speed drives are
Low starting current
Variable speed control over the load
Economical
Reduced power consumption
Variable frequency drives offer especially important energy savings
opportunities for existing and prospective induction motors in
variable-torque especially with such applications as centrifugal
fans, pumps and compressor load application.
These motors can also be started by Direct On Line but these can
cause damage to fuses because the demand for current and
overload the fuses causing them to trip if you do not take this into
account when selecting suitable fuses.
We can use starts electric motor by using a star delta starter this
reduces the current going into the motor and therefore we don’t get
in-rush of current and therefore tripping the mcb.
But due to the cost of the VFD`s or VSD`s I have chosen just to
Direct On Line starter, and use a MCB of higher rating.
Schneider Electric component number LE1D25N7, described
by Schneider as: DOL STARTER 25A 415V 50/60HZ PB I
So I have chosen Direct on line starter due to the cost over the Vsd
& Vsf drives. The direct on line starter will also protect the motor
from under-current, if one of the phases go`s down it will again stop
the motor.
8. 7
Braking arrangements
There is no Braking arrangement ,because a centrifugal fan does
not requirement for one and due to it being located straight onto a
housing of the centrifugal fan their will not be any room for one.
Section 5
Conclusion
In this report I have been asked to look at what is required to install
an electrical motor, for given situation and also provide electrical
protection as well as starting and braking arrangements, also had
to include fuse ratings and mcb ratings, as well what transmission
of power is best for this situation.
This is my opinion is the best way to connect a motor to the
electrical supply, in this investigation I have tried to keep costs
down.
