In broad terms there are two types of Electric Motors:
- Brush Type Motors – i.e. Angle Grinders Drills, Vacuum Cleaners…
- Induction type Motors – i.e. Grinders, Floor Sanders, Compressors …
Induction Type Motors may be:
- 240volt Single Phase – Refer to the Motor ID Plate for the Kw. Usually these motors have Capacitors fitted.
- 415volt Three Phase – Refer to the Motor ID plate which will show 3~ (3 phase) and show the Kw of the motor
To work out the generator size needed, multiply the machine Kw as follows:
- For a 240volt Single Phase machine: Kw of the Motor x 4 = Generator kVA
- For a 415volt Three Phase machine: Kw of the Motor x 3 = Generator kVA
So for example:
- Single phase 2.2Kw motor : therefore the Generator will need to be 8.8kVA
- Three phase 4Kw motor : therefore the Generator will need to be 12kVA
| Model | Phases | Kw of Motor | Amps Draw | Equation | Generator Size |
|---|---|---|---|---|---|
| Meteor 250 | 1 | 2.2 | 10 | (Kw X 4) | 8.8 KvA |
| Satellite 400 | 1 | 1.5 | 8.2 | (Kw X 4) | 6 KvA |
| Satellite 480 G3 | 1 | 2.2 | 10 | (Kw X 4) | 8.8 KvA |
| Satellite 650 G3 HDSPV | 3 | 7.5 | 15 | (Kw X 3) | 23 KvA |
| Satellite 760-6 G3 | 3 | 8 (2 X 4) | 16 | (Kw X 3) | 24 KvA |
| Satellite 760-12 | 3 | 16 (4 X 4) | 32 | (Kw X 3) | 48 KvA |
If you want to also run a Dust Collector on the same Generator:
Single phase Dust collectors are normally brush motors which are quite different in their demand on generators as they are not inductive loads. Because of this you can just get the watts of the unit and add it to your total above.
Three phase Dust collectors are normally Induction motors and the same formula applies to these as the floor grinders in the first chart.
| Model | Phases | Watts of Motor(s) | Amps Draw | Equation | Generator Size |
|---|---|---|---|---|---|
| DM-1360 | 1 | 1200 (1.2) | 5.2 | None | 1.2 KvA |
| DM-2660 | 1 | 2400 (2.4) | 10 | None | 2.4 KvA |
| DM-2780 | 1 | 3600 (3.6) | 15 | None | 5.6 KvA |
| RP 3000 | 1 | 2700 (2.7) | 12 | None | 2.7 KvA |
| RP 4000 | 3 | (5.5) | 12 | (Kw X 3) | 16 KvA |
Typical Examples:
240volt Grinder 2.2Kw = 8.8kVA, + Vac Motors x 2 = 6kVA Total 14.8 kVA Generator
415volt Grinder 7.5Kw = 22.5kVA, + 3 x Vac Motors = 9kVA Total 31.5 kVA Generator
415volt Grinder 7.5Kw = 22.5kVA + 3 phase, 5.5Kw Vac Motor = 16.5kVA Total 39 kVA Generator
It is recommended that you
- Always use site power to run 240volt Dust Extractors when possible
- Consider using two separate Generators, one for the grinder, and one for the dust extractor.
- Or, you can use a Parallel Box with two Makinex Generators to provide enough power. Example: You need 22.5kVA. So you can use a 16kVA and a 10kVA Generator = 26kVA
- It’s fine to have too much capacity, but not good to not have enough.
- Finally, use adequate heavy-duty cables to run these machines.
- It’s the amount of copper inside the cable that matters. 4.0mm2 Cables for single phase machines are often the minimum and cannot be bought ‘off-the-shelf’! Read this blog for more information on power cables.
- 2.5mm2 cables are normally adequate for single phase 1 and 2 motor vacuums.