3 Phase Grinders on a Single Phase Supply

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Mattsaxon
Posts: 32
Joined: 9 years ago

#1: Post by Mattsaxon »

Hi I thought I would post a little bit of info in case it is useful to people who either have a grinder and don't know if it is 3 phase or not, or know it is and want to find a way to run it on a single phase domestic supply. Maybe if anyone else has any experience of this topic they could share it here. I am a complete ignoramus regarding electrical matters so everything posted here is purely my own experiences and not in anyway to be taken as fact or professional advice.

A while ago I bought a 1950s Fiorenzato grinder from someone in Italy off ebay. As with all things ebay buyer definitely beware, but I think my grinder may have been a bit of a parts machine and the seller described it as 220V 50Hz which to be fair was the only information on the machine as there was no plate and this was just stamped into the base and the motor stator along with the number 511 on various parts which I take to be a batch or date number. Anyway having disassembled and cleaned it up and replaced the bearings which were shot, I naively assumed that I could just attach a UK plug and fire it up, which is when I realised I might have a problem. Whenever power was applied the motor turned approximately a half turn and then stopped, as the bearings were new and the shaft turned by hand I knew it wasn't seized, so I started to look into the electrical causes.

The strongest indicator that this was not a single phase i.e. domestic supply machine was the lack of either a capacitor or centrifugal switch to control the starting winding that a single phase motor has in order to start turning. The second indicator was that the 3 wires into the grinder - if it were single phase these would be live, neutral into the motor and earth to the housing etc, instead all 3 wires went into the motor windings. Finally putting a circuit tester across these wires showed continuity and the same resistance across each pair of wires which indicated this was 3 phase in a delta configuration.

From my research I read that it is possible to use a capacitor to act as a starting "winding" creating the asymmetry in the electric field to cause rotation, however many people express concern over the power loss and overheating this can cause. The solution I chose was to purchase a phase inverter or drive unit. These are available in ether 110v or 240v input and output to various voltages and power ratings. The unit is approximately 120mmW x 170mmH x 100mmD. Most units come with terminals to wire in switches etc, so it is possible as I did with mine to use the grinders original on off switch to switch on the drive unit, it would even be possible to fit a potentiometer to control the speed but depending on the type of drive this could reduce the effective power of the machine.

Anyway I hope this might be useful to anyone who finds them self in the situation I did.
p.s. does anyone know the model number for this grinder?

Cheers

matt



Beenbag
Posts: 330
Joined: 11 years ago

#2: Post by Beenbag »

Fiorenzato T69 ??