1.2.2. Graphic portion of the course work

The graphic portion of the work shall contain the following:

• assembly drawing of output shaft unit on A3 format sheet;

• data sheet for the unit assembly drawing, compiled on separate A4 format sheets.

1.3. Selection of task for the course work

A drive unit – is a device, including power source (electric motor 1, Figure 1) and a transmission mechanism (single-reduction unit) which serves to engage actuation mechanism 4. Couplings 2 serve to connect rotating shafts and to transmit the torque. The gear reduction unit is reviewed as a transmission mechanism herein.

Reduction unit is a toothed gearing to be mounted within sealed housingand serves to reduce frequency of rotation and increase the torque. Within reduction units the helical bevel gears are applied having high load-bearing capacity and smoothness. Scheme of the drive unit and general view of the reduction unit are outlined on Figure 1. The term “single reduction” specifies the number of gears .

Figure 1. Scheme of the drive unit and general view of the reduction unit

For the design work the benchmark data is as follows:

• capacity at outlet shaft;

• rotational frequency of outlet shaft;

• gear ratio of the drive unit.

The option of benchmark data for the design work is to be selected from Table 1 as per the last two digits of Test book number 21012/05.

Table 1.

The options of benchmark data for the design work

А	, kWт	В	, Rpm		Hardness option of gear as per Table 5
0	2,0	0	230	3,15	1
1	2,8	1	230	4	2
2	3,7	2	260	3,15	3
3	5,0	3	260	5	4
4	7,0	4	250	4	5
5	2,0	5	280	5	1
6	2,8	6	300	3,15	2
7	3,7	7	300	4	3
8	5,0	8	310	3,15	4
9	7,0	9	320	4	5

2. Guidelines of calculation portion of the course work

2.1. Electric-motor selection

The main benchmark data for electric-motor selection is as follows:

• outlet drive shaft capacity ;

• outlet drive shaft rotational frequency .

Electric-motor power requirements: ,

where – totalefficiencyof reduction unit;

–number of bearings.

Furthermore, due to the lack of additional gears in the drive, then , where  – transmission ratio of a gear.

Recommended values of toothed gear and bearings are outlined on Figure 2.

Figure 2.

Gear and bearings efficiency

Transmission components	Average value
Toothed gear	0,96…0,98
Rolling bearings (one pair)	0,99

Electric-motor rotational frequency:

.

Electric-motor rated capacity is to be:

.

Rated capacity is the capacity that electric motor is capable to produce continuously without overheating above permissible temperature.

In general machine building industry three-phase short closed asynchronous motors of 4A series (4 stands for serial number of series; A stands for asynchronous type of the motor) are used. (Table 3).

Table 3.

Rated capacity and rotational frequency of 4A type motors.

, kW	Synchronous frequency, revs per minute
	3000	1500	1000	750
0,75	4А71А2/2840	4А71B4/1390	4А80A6/915	4А90LA8/700
1,1	4А71В2/2810	4А80A4/1420	4А80B6/920	4А90LB8/700
1,5	4А80А2/2850	4А80B4/1415	4А90L6/935	4А100L8/700
2,2	4А80В2/2850	4А90L4/1425	4А100L6/950	4А112MA8/700
3	4А90L2/2840	4А100S4/1435	4А112MA6/955	4А112MB8/700
4	4А100S2/2880	4А100L4/1430	4А112MB6/950	4А132S8/720
5,5	4А100L2/2880	4А112M4/1445	4А132S6/965	4А132M8/720
7,5	4А112M2/2900	4А132S4/1455	4А132M6/970	4А160S8/730
11	4А132M2/2900	4А132M4/1460	4А160S6/975	4А160M8/730
15	4А160S2/2940	4А160S4/1465	4А160M6/975	4А180M8/730

Note.

To make the above table more indiscrete after the slash the rated speed (rpm) is indicated that is not included into the motor symbol.

The following parameters are to be included into the explanatory note for this type of the motor. motor symbol;

• rated capacity, кВт;

• speed under rated load , rpm.