Convert 3 Phase Motor

[nel]

hi i want to convert my 3 phase motor to a single can i convert 5.5 hp to a single motors? i wish u can help my problem pls.

what did i do?

 

[Y2KEDDIE]

I've used phase converters to run lathes, milling machines, and valve operators when 3 phase power is not available. I prefer to use VFD (variable frequency drives) as these are much more efficient and caplable of full load speed and torque, but static converters are a lot less expensive if you just want to get something moving.

You can run a (lightly loaded) three phase motor from a single phase source by using a " staticphase converter". This is a device which has a set of capacitors, and relays set up to create a phase shift of the single phase input. They are about 70% efficient typically so you won't get the full 5.5 hp from your motor. They work well with light loads where you have just one motor to contend with A 3-7 hp unit costs about $220.

For heavier loads you need a "rotory phase converter" , this device has it's own internal "motor" which helps create the phase shifts required. Typically with a 10 HP nameplate you have an 8 HP starting capacity. This unit is about $1400, which is close to what a VFD costs. A 5 Hp unit costs about $800 .

You can buy these from Mc Master Carr industrial supply.

 

[woodchips]

You are going to have trouble finding a single phase 230V inverter that will run 5.5hp, 4.2kW. They seem to stop at about half that simply because that is the most you can draw from a normal power socket.

Static converters work fine, but you must use a 400V one with the motor wired in star. They are not happy things with the motor in delta, do a search. Contrary to popular belief they will provide 100% of the motor power as well. Don't need the rotary converter unless running more than one motor from the same static converter.

Depends how good your engineering is, 400V safety mostly, but they are easy to make yourself for a lot less than a bought item, just getting suitable transformers.

Don't forget that a static converter will still be drawing a lot of current from the single phase supply, you need industrial plugs and sockets etc.

 

[Y2KEDDIE]

Another retail source (in the US) for Static or Rotary phase converters is the Grizzly Tool Company. (Do a Google search). Their units are for use with their woodworking and metal working machines. Most 3 phase motors have dual 220/440v windings and these converters are made for these.

Typically static converters work well with lightly loaded machines where low starting torque is required (the machine can get up to speed quickly)

The rotary converter is needed where high starting torque is needed such as a compressor..

 

[nel]

if i try to use capacitor 40 uf,370 vac to run the 2hp motor, to covert to a single phase. what happen to the motor?

 

[nel]

can i make static converter?

how?

 

[Y2KEDDIE]

A simple capacitor added will not make a staic converter.

Your concept of adding a capcitor possibly mimicks a capacitor start motor where you shift the input phase of one winding to get the motor field rotating.

The static converter does shift the phases but to each winding and at percise timing. The unit I have has several large value (non polarizedcapacitors), relays, and a 2" x 2" circuit boad full of electronic componets.

Another unit I have has a bank of capacitors and several potential relays. The capacitors wee selected for specific match ing of the inductance of the motor windings.
There is a lot more going on than just adding a sigle capacitor.

 

[woodchips]

The capacitor, 40uF, just adds a phase shift from the two phases from the 400V transformer to the third motor phase. The capacitance needed is simply found by putting a voltmeter across any two phases and adjusting the capacitor value so both phases have equal voltage. Easy enough to get within 5V.

Starting is another problem and you will need much higher capacitance values to get the required phase shift, again use a voltmeter. Typically about 20uF per HP to run, 150uF per hp to start.

The other components are just a time delay to switch the start capacitors out once the motor is running at a reasonable speed and the current has dropped.

You will get resonance effects with the motor and capacitor and need at least 450V AC capacitors.

Again, this is 400V, it bites, only play if you know what you are doing.

 

[nel]

thanks to all for the advice..i hope now i can solve my problem.,.,


thank you.,.,..