FREQUENTLY ASKED QUESTIONS
Q. Why consider a generating set?
There are 3 main reasons:
- There is no other source of electricity available.
- There is insufficient capacity from the commercial supplier to meet requirements.
- An alternate source of electrical power is necessary in the event of a periodic or sustained loss of commercial mains power. Such power losses can seriously affect different organisations:
- In Hospitals – a loss of patient monitoring and/or life support.
- In Data Centres – a loss in data processing and some data.
- In offices and ACCOMMODATION buildings – a loss in power, lighting and lifts.
- In Processing Plants – loss of production, raw material and/or product.
Q. What type and size of Generating Set do I need?
There are many types of Generator Sets; there are single phase or three phase units, petrol, diesel, gas or electric motor driven. They can be basic manual start, automatic start or continual running units. They come in open form, WEATHERPROOF enclosed, sound attenuated, fixed, skid-mounted or trailer mounted. When sizing a Generator Set consideration should be given to the following:
Lighting and heating: The total resistive load can be calculated by adding all the installed resistive loads in kilowatts (kW).
Motors and transformers: Consideration must be given to the size, type and starting method of each electric motor.
|Rating||240 Volt- SINGLE phase portable Generators|
|1 kVA||Small PA systems, TV, Video and lighting to 700 Watt, small drills to 900 Watt.|
|2-3 kVA||P.A systems, video and audio equipment, small electrical tools, kango hammer, drills, saws, lighting to 2800 Watt.|
|6-8 kVA||Multiple use of tools as above, small bench cut-off saws, 240 Volt 140 amp welder, air compressor, Heater, Urns, Mobile fridge and 1.5 kW air conditioner.|
|Rating||415/240 Volt- Three phase silenced diesel Generators|
|20-25 kVA||Construction power- ablution block, site sheds, lunch room, approx 4-6 sheds subject to heating and air con appliances, 5000-6000 Watts per phase, 3 phase audio and lighting, electric motor starting up to 7.5 kW, Approx. 8 food stalls.|
|50-100 kVA||Construction power- Approx 15-25 sheds, small office buildings, electric motor starting 15-30 kW, lighting and audio, approx 15-30 food stalls, large video screens.|
|100-1000kVA||Construction, mining, large refrigeration, power outages, industrial and commercial power, tower cranes, back up power supply, factory units, entertainment, large motor starting.|
Q. Why is the size of a generating set often measured in kVA?
Apparent power is defined as the power that is “apparently” absorbed by a system. That is, the product of current times voltage tells us a device appears to be using a certain amount of power. However, this does not take into account the fact that the device can store (or delay) current or voltage and this results in the CALCULATIONS being slightly skewed.
Apparent power is useful when we have a device like a diesel generator, where the wires inside have a limited capacity to pass current and we may not know in advance what will be connected to the generator. In other words, it doesn’t matter what the delay (or phase angle) is, the generator can only allow a limited amount of current to pass through its wires.
Because of this, many generators (and most transformers) are rated in volt-amperes (VA), or thousand-volt-amperes (kVA). The apparent power in KVA multiplied by the power factor
(PF) is the real power in kilowatts (KW).
Q. What type of oil should I use in my generating set?
All modern engines, whether they are diesel or petrol, have specific requirements in relation to oil specification. It is therefore important that individual engine maintenance and operation guidelines be FOLLOWED when selective oil type and quantity for routine maintenance. If in doubt, please refer to the supplier or Distributor representative.
Q. Where can we obtain original spare parts for the generating sets sold by Generator Power?
Generator Power carry the more frequently called for spare parts including filters, gaskets, belts, AVR’s in our warehouse. For those parts that are not always “off the shelf”, we make it our business to obtain these items quickly and at competitive pricing so that we can keep YOUR downtime to a minimum.
Q. How much fuel will my generator consume?
|kVA||kW||AMPS PER PHASE||Fuel Cons L.P.H. @ 50% load (approx.)||Fuel Cons L.P.H. @100% load (approx.)|
Q. What are some useful electrical formulas for quick calcs?
|To Obtain||SINGLE Phase||Three phase|
|Kilowatts||V x I x pf |
|1.732 x V x I x pf |
|kVA||V x I |
|1.732 x V x I |
|Horsepower When required kW Known||kW |
0.746 x EFF (GEN)
0.746 x EFF (GEN)
|kW input when HP Known||HP x 0.746 |
|HP x 0.746 |
|Amperes When HP Known||HP x 0.746 |
V x pf x EFF
|HP x 0.746 |
1.732 x V x pf x EFF
|Amperes When kW Known||kW x 1000 |
V x pf
|kW x 1000 |
1.732 x V x pf
|Amperes When kVA known||kVA x 100 |
|kVA x 100 |
1.732 x V
|Frequency (Hz)||Poles x RPM |
|Poles x RPM |
|% Voltage Regulation||100(Vnl – Vfl) |
|100(Vnl – Vfl) |
|The FOLLOWING abbreviations are used in this table|
|V = voltage||RPM = revolutions per minute|
|I = current||kVAR = reactive kilovolt-amperes|
|KW = Power in Kilowatts||EFF = efficiency|
|KVA = kilovolt – amperes||NL = no load|
|HP = horsepower||FL = full load|
|Pf = power factor|