Actually, both equipments are "Resistive Loads": we use to call them in two different ways since they are intended for two different purposes.
Standard technical specifications
| Specification | Description |
|
Rated ohmic value tolerance |
± 5% related to each resistive element. |
|
Airflow direction |
Vertical direction, from bottom to top. |
| Fan standard specifications |
Conveyor in carbon steel, impeller in polyamide reinforced with glass fiber (PAG). The device will be supplied with its test balancing certificate. Motor specifications: IP55 protection, F insulating class, EEF2 efficiency class, S1 service, tropicalized. Unducted frame. |
| Electric power connections | On screw terminals for sizes up to 64 kW. By bolting on copper bars for bigger sizes. |
| Handling | Holes for forklift on bottom, eye-bolts on top |
| Controls | Remote. Connections predisposed on appropriate terminal strip. |
| AUX power supply | From external grid |
Resistive Loads
We use to call "Resistive Loads" (differently from the "Dummy Loads", described below) the ones intended for performance tests on power generating systems (mainly Gensets or UPSs). They are characterized by several increasing power steps, from 1 kW (the lowest) up to over 250 kW for the biggest one.
The table shown below reports the standard power sizes of equipments, referred to a 400 V - 50 Hz supply.
| kW |
Dimensions (WxHxD,mm) |
Nr.of steps |
Airflow (m3/h) | Weight (kg) |
| 31 | 573x1015x825 | 5 |
5.750 | 95 |
| 63 | 573x1015x825 | 6 |
5.750 | 105 |
| 95 | 700x1350x825 | 7 |
9.950 | 150 |
| 127 |
700x1350x825 | 7 | 9.950 | 165 |
| 191 | 700x2050x1370 | 8 | 11.500 | 310 |
| 255 | 700x2050x1370 | 8 |
19.900 | 360 |
| 351 |
1150x2050x1370 | 9 |
33.800 | 480 |
| 415 |
1150x2050x1370 | 10 | 33.800 | 540 |
| 511 |
1150x2050x1370 | 9 | 38.200 | 610 |
| 607 | 1150x2050x1370 | 10 | 38.200 | 690 |
The resolution of power values is as high as possible (1 kW on the whole scale values) to allow a thin modulation of load power, especially near to the rated power of generator, to verify with a good accuracy if the real performances are in compliance with the declared ones.
We gave a particular care to the sizing of cooling airflow, which must prevent the power loss due to the thermal drift and guarantee the maximum precision of test measurements.
During long duration test sessions, performed in real working conditions and at full load power, we have could test that power loss of our loads due to thermal drift is less than 2%.
In summary, this kind of resistive load is distinguished by a very high resolution on power scale values (min. variation: 1 kW) and by a high steadiness of load power, thanks to a plentiful cooling.
The system modularity also allows future expansions of power, by adding further loads with the actually needed power and number of steps.
Dummy Loads
An insufficient thermal equilibrium, due to a too low temperature, decreases the machine efficiency.
Moreover, the low pressure into cylinders is not able to fully expand the sealing rings of pistons: that fact causes fuel unburned and some lube oil leaking into fire chamber.
The consequences of this wrong running mode are dark smoke emission and settling of oily and carbon residues into cylinders, filters and drains with potentially destructive effects.
To avoid such troubles, under a definite percentage of the rated power (typically less than 60%) are used dummy loads, which easily can be turned on or off by an ampermetric relay, so that the power output of diesel engine is always high enough to ensure good operating conditions.
See some of the main features in the table below (powers referred to a 400 V - 50 Hz supply):
| kW | Dimensions (WxHxD,mm) | Nr.of steps |
Airflow (m3/h) | Weight (kg) |
| 32 | 573x1015x825 | 2 | 5.750 |
95 |
| 64 |
573x1015x825 | 2 | 5.750 |
100 |
| 96 | 700x1350x825 |
3 | 9.950 | 145 |
| 128 | 700x1350x825 | 2 | 9.950 | 155 |
| 128 | 700x1350x825 | 4 |
9.950 | 155 |
| 256 |
700x2050x1370 | 2 | 19.900 |
350 |
| 256 | 700x2050x1370 |
4 | 19.900 | 350 |
| 512 | 1150x2050x1370 | 2 | 33.800 | 590 |
| 512 | 1150x2050x1370 | 4 | 33.800 | 590 |
Dummy loads are also very important for periodic tests of emergency systems in all those situations (e.g.: hospitals) in which it is mandatory that the perfect efficiency of the machine is constantly verified.
In this context are not so important load steadiness and a high resolution of power scale, which is therefore divided into few large steps. This means that can be used materials and design criteria less extreme, all resultant in a cheaper solution.
- All specifications listed above are approximate and can be changed because of design improvements.
