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Diesel-generator sets

The loads unbalance problem and solution.

The solution of the unbalance problem under three-phase and single-phase loads simultaneously is the difficult task. Besides at the limited power the phase unbalance tends to the unreasonable increase of diesel generator power and as a result to the increase of minimal load capacity.

The solution is the installation of three-phase balancing transformer between DGS and electrical customer.

The transformer removes the unbalance under customer electric supply from diesel generator set or power grid. At the same time it accepts the 100% load unbalance. The maximum single-phase power provided by balancing transformer at diesel generator supply is not over 65% of DGS power under no load of two other phases.

The main technical parameters of transformer is written on tables 1,2.

Table 1

nominal load power, кVА	10;16;25;40;63;100;160;200;250;400; 630;1000
Nominal frequency, Hz	50
Nominal line voltage, В	380
Primary winding nominal current, А	15;24;39;60;96;150;240;300;375;600; 950;1500
Load current unbalance, %	100
Heat resistance class	В
Overload class according to ГОСТ 12.2.007.0	01

Table 2

Output power , кVА	Overall dimensions, mm	Weight, кг
10	420х300х410	50
16		65
25		70
40	550х350х500	95
63		110
100		160
160	800х420х680	250
200		290
250		320
300	850х500х870	370
400		430
630	1230х840х1020	740
1000		850
.

Besides the main function is phase load balance the transformer has the additional functions:

1. The transformation of three-phase grid into single-phase one:
   • - with galvanic separation between the supply grid and customer;
   • - with galvanic separation between the supply grid and customer and changing (increase or reduce)of output voltage;
   • - without galvanic separation between the supply grid and customer and changing (increase or reduce)of output voltage;
   • - without galvanic separation between the supply grid and customer;
2. transformation of three-phase three-wire grid into three-phase fought-wire grid (i.e. making of the neutral wire to connect with phase load).

The weight and dimension characteristics for balancing transformers which transform three-phase grid into single-phase one without galvanic separation (ТСТ-О) are written on table 3.

Table 3

Output power , кVА	Overall dimensions, mm	Weight, кг
10	420х300х410	80
16		100
25	550х350х500	115
40		140
63	800х420х680	210
100		305
160	850х500х870	410
200		650
250	1230х840х1020	720
300		805
400		910
.

Weight and dimension characteristics for balancing transformers which transform of three-phase grid into single-phase one with galvanic separation (ТСТ-О) are written on table 4.

Table 4

Output power , кVА	Overall dimensions, mm	Weight, кг
10	420х300х410	110
16	550х350х500	180
25	800х420х680	290
40		400
63		540
100	850х500х870	680
160		910
200		1230
250	1230х840х1020	1520
300		1680
400		2150
.

The transformation of three-phase grid into single-phase one is actual at the connection with single-phase loads located at a high distance from power supply (DGS and others). Moreover three-phase grid capacity is three times higher than single-phase one. This lets transfer higher power or reduce the supply cable section.

DGS
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