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Static phase converters

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jb3cx:
Here's my penny's worth .for the last 20 years I have used a transwave static converter 7.5 kw
I run a bridgeport mill ,Harrison m 250 .there are only 2 problems I have came across .(1) the minimum load is 1.5 kw .(2) if I have the Harrison in high gear ,on startup it labourers up to,top speed
I have been told that I need a bigger feed cable from the house to the workshop .ok I will get round to it sometime .what I have been doing is to start the bridgeport first thus acting as a pilot motor ,and I have not had any problems starting the m250 in high gear .also it's a lot quieter than running a rotary converter .olso the other downside of using a converter of this size is the min loading 1.5 kw i.e. 2hp
Therefore on the other machines I have I use small inverters .
Peter

martin33100:

--- Quote from: vintageandclassicrepairs on December 19, 2017, 03:25:18 PM ---Hi Phil,
Yes I'm sure of the motors connections, it is different to the "usual" 380/220v dual voltage configuration
The plate on it shows 380-420v only and is Delta connected with each phase connected to two internal winding ends,
Way back when! there was a 550/600 volt system used in Industry, maybe it could have been star connected for the higher voltage  :scratch:

Martin and All,
With the Transwave static converter the motor is started by applying line voltage across two phase connections and capacitors connected from one phase to the third phase connection
(same principal as a single phase capacitor run motor)
The magnetised  rotor spinning within three 120 degree mechanically spaced windings generates the third phase
That is how a rotary converter works, the pilot motor acts as a generator ( a 2850rpm motor is preferable for this but not essential)

To be honest I was disappointed with the performance of the Transwave that came with my lathe
The phase voltages were very high, getting over 500v depending on the switch setting
The motor buzzed and growled and drew high current on no load
It tested out ok with my motor tester, inductance and resistance wise

I spent almost 30 years working on power generation and associated electrical plant so am fairly confident of my abilities (electric motor wise) :zap:  :lol:

The PITA situation is that there's a 3 phase transformer on my boundary fence
But the capital and running costs of installing 3phase is unrealistic :bang:

John

--- End quote ---
I am guessing it was a static converter your lathe came with?.

vintageandclassicrepairs:
Hi Martin,

--- Quote ---I am guessing it was a static converter your lathe came with?.
--- End quote ---

Yes it is, Rated about 4Kw

For the price of a new Transwave I would prefer to go for an inverter instead
 
I have inverters on the 3hp milling machine and 7.5hp (5.5Kw) Colchester
These run sweet as a nut

I am going with the 3hp single phase motor on the Harrison simply because it was free and the wiring to
it is there from the old lathe that has gone to a new home

John

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