- Joined
- Aug 18, 2011
- Messages
- 120
I have an Excello milling machine that the motor was rewound to 440v only. I found this article at the link below.
http://www.inverterdrive.com/HowTo/240V-Supply-to-a-400V-AC-Motor/
(quote)
It is not uncommon for home workshops to include machinery requiring a 3 phase 400V supply (often marked 380 – 420V). This can appear to be a problem where a 3 phase supply isn’t immediately available. However, it is possible to run such equipment from a domestic 230V supply using nothing more than an off the shelf Inverter Drive.
If you are unable to change the connections or windings to 240V 3 phase, then read on for the next best solution... The speed of an Electric Motor is determined by Voltage and Frequency. So, a 400V 50Hz Motor will run at rated speed at 400V/50Hz and half rated speed at 200V/25Hz. Provided this Voltage/Frequency ratio is maintained, the Motor will operate at full Torque – ideal in a Lathe application where speed must remain constant even when a load (the tool) is applied (to a work piece).
An Inverter Drive is not only able to convert a 230V single phase supply to 230V 3 phase but it also controls both the output Frequency and Voltage to maintain the correct ratio. It therefore follows that a 400V/50Hz Motor will operate normally at 230V and 29Hz, just at two thirds the speed (eg. 1000rpm instead of 1500rpm).
The parameter to set in the Inverter Drive is "Base Frequency" or "Nominal Frequency" (depending on the manufacturer) in Motor Settings.
Above 29Hz, the Motor will become progressively "Under-Fluxed" (Torque will reduce) as a 230V Inverter does not normally exceed its supply voltage. However, this will only be evident if the Motor is fully loaded. If it is, the Motor will look for more current to meet the load. A correctly set Inverter will provide protection against this by reducing the speed automatically to bring the load current under the maximum "over-current" set.
It is important to note that when an Inverters output voltage does not match the Motors rated voltage, specifying the correct Inverter is not a simple case of matchingkW and it should instead be matched to the Motor full load current.
Full Load Current of 400V x 50Hz 4 Pole motors are as follows:-
(endquote)
If I get this right, I should be able to set the drive at 40hz, my 11/2hp 1200rpm 440v motor should run 1hp, 800rpm.(machine 66- 2500 rpm spindle, running 44-1630 rpm with gearbox and variable belt drive) I loose power only if I want to run the motor at higher rpm/hz ,probably won't be a problem with smaller cutters.
This works on a lathe, should be no problem on a mill.
What do you think?
Darcy
http://www.inverterdrive.com/HowTo/240V-Supply-to-a-400V-AC-Motor/
(quote)
It is not uncommon for home workshops to include machinery requiring a 3 phase 400V supply (often marked 380 – 420V). This can appear to be a problem where a 3 phase supply isn’t immediately available. However, it is possible to run such equipment from a domestic 230V supply using nothing more than an off the shelf Inverter Drive.
If you are unable to change the connections or windings to 240V 3 phase, then read on for the next best solution... The speed of an Electric Motor is determined by Voltage and Frequency. So, a 400V 50Hz Motor will run at rated speed at 400V/50Hz and half rated speed at 200V/25Hz. Provided this Voltage/Frequency ratio is maintained, the Motor will operate at full Torque – ideal in a Lathe application where speed must remain constant even when a load (the tool) is applied (to a work piece).
An Inverter Drive is not only able to convert a 230V single phase supply to 230V 3 phase but it also controls both the output Frequency and Voltage to maintain the correct ratio. It therefore follows that a 400V/50Hz Motor will operate normally at 230V and 29Hz, just at two thirds the speed (eg. 1000rpm instead of 1500rpm).
The parameter to set in the Inverter Drive is "Base Frequency" or "Nominal Frequency" (depending on the manufacturer) in Motor Settings.
Above 29Hz, the Motor will become progressively "Under-Fluxed" (Torque will reduce) as a 230V Inverter does not normally exceed its supply voltage. However, this will only be evident if the Motor is fully loaded. If it is, the Motor will look for more current to meet the load. A correctly set Inverter will provide protection against this by reducing the speed automatically to bring the load current under the maximum "over-current" set.
It is important to note that when an Inverters output voltage does not match the Motors rated voltage, specifying the correct Inverter is not a simple case of matchingkW and it should instead be matched to the Motor full load current.
Full Load Current of 400V x 50Hz 4 Pole motors are as follows:-
- 5.5kW (7.5HP) - 11.4A
- 4.0kW (5.4HP) - 8.6A
- 3.0kW (4HP) - 6.4A
- 2.2kW (3HP) - 4.9A
- 1.5kW (2HP) - 3.6A
- 1.1kW (1.5HP) - 2.7A
- 0.75kW (1HP) - 2.0A
- 0.55kW (0.75HP) - 1.5A
- 0.37kW (0.5HP) - 1.2A
- 0.25kW (0.33HP) - 0.8A
- 0.18kW (0.25HP) - 0.63A
- 0.12kW (0.16HP) - 0.44A
- 3.0kW (4HP) - 12.6A
- 2.2kW (3HP) - 9.8A
- 1.5kW (2HP) - 7.5A
- 1.1kW (1.5HP) - 6.7A
- 0.75kW (1HP) - 4.7A
- 0.55kW (0.75HP) - 3A
- 0.37kW (0.5HP) - 2.4A
- 0.25kW (0.33HP) - 1.7A
- 0.18kW (0.25HP) - 0.63A
- 0.12kW (0.16HP) - 0.44A
(endquote)
If I get this right, I should be able to set the drive at 40hz, my 11/2hp 1200rpm 440v motor should run 1hp, 800rpm.(machine 66- 2500 rpm spindle, running 44-1630 rpm with gearbox and variable belt drive) I loose power only if I want to run the motor at higher rpm/hz ,probably won't be a problem with smaller cutters.
This works on a lathe, should be no problem on a mill.
What do you think?
Darcy