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Join Date: Aug 2017
Posts: 6

2 Speed 3 Phase Motor Question

08/27/2017 8:25 AM

Hi to all

not a professional in this field but work in engineering /auto electrics and stumbled upon this site researching my current home shop gift

I've been given a rather well-made mill drill by abrboga u2508 which has a 2 speed 3 phase motor@415 volts now at home i only have 3 phase 220 volts looking at the motor plate it will only do 415

I have worked out its a dahlender set up in this doc it's the

Two Speed Constant Torque Motor

http://www.lmphotonics.com/InductionMotor/dahlander_motor.php

this was kindly posted by someone on this forum

Now in the past when I've had a 3 phase motor 415 which has had the star connection in the stator windings which i have brought out so that it would run on 220 volt

I removed the stator from the machine and all 6 joints are easily accessible can I reconnect the 6 coils (12) wires in a format that will enable it to run on 220volt the dual speed is not needed as will use a vfd looking at the motor coil arrangement it looks feasible but this not my field of expertise so some advice please

I do know i could use a 220 to 440 volt transformer and a 380 volt vfd overrated to run on single phase

but both items would require buying

Replacing the motor is hard due to the stator being machined to fit in a mill head with gearbox although this is possible as is getting the stator rewound for 220volt

Thanks for taking the time to read my ramblings

Andrew Bishop Uk

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Guru

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#1

Re: 2 speed 3 phase motor question

08/27/2017 10:17 AM

For the avoidance of doubt......

Is your supply 3 phase, 3 wire, 220 volt wire to wire?

415V is a common 50 Hz line-line voltage, but typically a 415V/240V, 3 phase 4 wire supply with 240V to earthed neutral.

Does the motor rating plate have a terminal diagram with letters/numbers on it? If so a photo image would enable explicit connection advice by "posters" in reply to your question.

What standard is given on motor plate? Following diagram uses terminal code to USA convention. Note LOW speed is delta connection & HIGH is star

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#2
In reply to #1

Re: 2 speed 3 phase motor question

08/27/2017 1:17 PM

Hi thanks for the reply

uk mains domestic 220 live to neutral so I normally use caps to create the 3rd phase or in this case i have a spare single to three phase inverter that i was going to use

your drawing is what i think i have

the top right is the housing that the stator goes in

I was thinking that i could make a break at T1 T2 T3 and run the 2 coils in parallel leaving in a delta config but really looking for guidance

Thanks Andrew

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#5
In reply to #2

Re: 2 speed 3 phase motor question

08/27/2017 6:10 PM

Unfortunately, the motor has 6 windings because it needs U-V-W-U-V-W [6 phase windings] around the stator circumference for the low speed connection. It does not have two windings per phase like a dual voltage, single speed motor.

Since you propose the delta connection, I assume you want the low speed 1310 rev/min.

Unfortunately, 220V on 415V winding is only 28% of torque at rated voltage.

Raising the voltage with a transformer(s) or rewinding are the options. At least with transfo, you can have two speeds.

I guess 3 single phase 220/240V 500VA transfos with motor side secondary windings in star is possible to get 415V from 220V line-line 3 phase. Microwave cooker transfos (the loud hum type) are over 500VA & can be rewound to a desired ratio after knocking out the magnetic shunt and High Volt winding.

You have not told what voltage your 3 phase inverter gives line-line.

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#6
In reply to #5

Re: 2 speed 3 phase motor question

08/28/2017 3:38 AM

Hi thanks for the reply although I have measured across 415 volt before 210 phase to phase.

Have not done my inverter output will measure today and report back

I like the idea of using microwave transformer

I may have a old spot welder at work with 220 primery if i still have it it was 11kva

Thanks Andrew

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#7
In reply to #5

Re: 2 speed 3 phase motor question

08/28/2017 4:04 PM

Not much luck measuring inverter line to line

with a 1.5kw motor runing fluke meter read 11 volts ac although at 53hz as opposed to 50hz with out putting a scope on it to look to see how pure the sine wave is I might try it on the machine as its only going to do drilling as I already have a cnc mill

the inverter says 3 phase 200 to 240 volts so that's all I have to go on but I would guess line to line 110

Thanks for the advice and help

Andrew

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#10
In reply to #7

Re: 2 speed 3 phase motor question

08/29/2017 10:32 AM

Please excuse my stupidity...

If, for LOW speed, you put the A and B windings in parallel, rather than series, the required voltage is 415/2 = 208 line to line which may suit your inverter, which I can only think is to provide a 115V to neutral 3 phase supply which is 200/115 or 208/120 line-line/line-neutral maybe where folk have "115V wall sockets". Since the star or Y HIGH speed connection is 240V per winding, 240 line-line in Delta should also be OK.

I am puzzled by reported inverter performance, perhaps 1.5kW motor is too much,difficult to believe it rotates with just 11V?. What do you get with 240V 100 watt incandescent bulb (or 200W halogen floodlight) per phase? Start with three lamps star connected, in view of doubt about voltage.

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#11
In reply to #10

Re: 2 speed 3 phase motor question

08/29/2017 1:09 PM

Thanks for your suggestion ref A and B thats what Im going to try

as far as the inverter is concerned it works fine powering 1.5 kw spindle on the cnc mill it going to be retired as spindle control on the new interface board is going over to modbus

Bit of a mystery 11 volts ac but on a auto ranging fluke meter not quite sure whats going on

Your suggestion A and B might just work and it also if I move this to the main workshop

that has 415 3 phase it can be use in it original format

Thanks Andrew

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Guru

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#12
In reply to #11

Re: 2 speed 3 phase motor question

08/29/2017 1:57 PM

Digital meters can go weird on pulsed waveforms. Time to get out the analog multimeter - EMC test houses like their AVO 8 meters as a reality check.

Best wishes for machine motor.

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#3

Re: 2 Speed 3 Phase Motor Question

08/27/2017 2:30 PM
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#4
In reply to #3

Re: 2 Speed 3 Phase Motor Question

08/27/2017 4:18 PM

thanks hadn't come accross that one

but still no real soulution its a shame you cant search for stators with "x" id and "x"od

Thanks Andrew

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#8

Re: 2 Speed 3 Phase Motor Question

08/28/2017 7:24 PM

Motors are specifically designed for VFD service. This may (I say may because I am not an "expert" in this field) not work with a VFD no matter how you configure the wiring.

JRaef, redfred, or RAMConsult (and I am sure several others here) would probably know for sure.

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#9

Re: 2 Speed 3 Phase Motor Question

08/29/2017 3:34 AM

If, as indicated, a VFD is available, then one doesn't need the complication introduced by the presence of a 2-speed motor in place of a single speed one. Further, one might use the two-speed motor in single speed mode when operated off a VFD.

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