Macfarlane Generators Power Calculator

Guide to units:

HP
=
Horsepower
kW
=
Kilo Watts
kVA
=
Kilo Volt Amps
I
=
Ampere or Current
V
=
Volts
PF
=
Power Factor

 

Calculating Ampere (I), given kVA
Phase
1, 2, 3
Generator
kVA
Volts
Required
= Ampere
I
 

 

Converting kVA to kW
kVA = kW  
Converting kW to kVA
kW = kVA  

 

Converting kW to HP
kW = HP  

 

What size genset is needed to start a 3 phase electric motor Direct on
Line (DOL) start
HP of
Motor
= Generator
kVA Required
 

 

Generator Size to Start Motors

Instructions: Fill in the HP of the motor(s) in their starting sequence, select the start method (DOL - Direct On Line or Star Delta) and press Calculate. The required generator size will then be displayed at the bottom.

3 Phase (415 volt @ 50Hz)
1 Phase (240 volt @ 50Hz)

Starting Sequence Motor HP Start Method
DOL / StarDelta
Run Variable Phase Current Starting Value Total
Run
Current
Total
Start
Current
1 /
2 /
3 /
4 /
5 /
6 /
Generator Size for Starting with: kVA*
Generator Size for Running with: kVA*
Generator Size Recommended: kVA*

 

* Please NOTE the above calculations are an estimate only because other factors such as site conditions, motor efficiencies and iron losses are not taken into consideration.

Power Consumption Calculator


ApplianceRated WattsRated kVARated kVA
 (Appliances)(To operate appliance)( To start appliance)
Air Conditioner (Evaporative model)275-10000.34-1.251.36-5
Air Conditioner (Reverse cycle)200-25000.25-3.131-12.5
Clothes Dryer240033
Coffee Percolator5500.690.69
Can Opener1000.130.52
Deep Freezer5000.632.52
Disposal Unit6500.813.24
Dishwasher1000-30001.25-3.751.25-3.75
Domestic Water Pumps275-10000.34-1.251.36-5
Exhaust Fan400.050.2
Food Processor5000.632.52
Floor Polisher3500.441.76
Frypan14001.751.75
Hair Dryer15001.881.88
Hotwater Service2500-30003.13-3.753-13-3.75
Iron800-15001-1.881-1.88
Kettle or jug1600-30002-3.752-3.75
Lights25-2000.03-0.250.03-0.25
Microwave15001.881.88
Oven4000-80005-105-10
Radio600.080.08
Radiator1000-25001.25-3.13115-3.13
Refrigerator (home)3000.381.52
Sewing Machine600.080.32
Space Heater20002-52.5
Television75-2000.09-0.250.09-0.25
Toaster250-12500.3-1.560.3-1.56
Washing Machine500-30000.63-3.752.52-15
Welder 140A50006.258 min

Please Note:

Inductive loads (typically electric motors, electric pumps, electric compressors and air conditioners) require 6-8 times more current to start than to run. Most generators can provide 100% overload for start up purposes. A 1 Hp electric motor therefore will require 3-4kVA for start up. Once the 1 Hp electric motor has started, it will only consume 1 kVA leaving a extra 2-3kVA available for other appliances.

However, the newer 'Inverter' style generators may be more efficient and capable of starting higher loads.

Generator Selection

The generator size must be equal or greater than the total consumption of all applications. The higher starting requirement must be taken into account accordingly. To maximise the generator potential, the largest electrical motor should be started on its own and further appliances should only be switched on thereafter.