Stewart PrinceElectric Motor Drive SystemsDN4K 35

By

Electric Motor Drive Systems

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

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

3

Section 1

Selected motor

Manufacturer ABB

Output Kw

Motor type

Product code

Speed R/min

Eff on full load 100%

¾ of load 75%

Power factor cos ϕ at 100%

Current In

A

Current Is In

A

Torque

Tn

Nm

11 M3BPV 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.

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.

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.

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

7

from under-current, if one of the phases go`s down it will again stop the motor.

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.

8

Section 6

Appendix 1

9

10

11