Re: Bridgeport Stepper Voltage/Current?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Les Newell <les@l...> wrote:

> Hi Kevin,
>
> The original stepper drives run at above 100V. However, Gecko G201s

at

> about 70V and full current will run them quite well. You can make a
> cheap power supply by reusing the big 110V transformer. If you wire

the

> transformer for twice your mains voltage you end up with 55V out.

In
my

> case the mains is 230V (measured) so I wired my transformer for

460V. As

> some of the auxiliary systems on my machine need 110V I wired them

to

> the 230V input of the transformer. As the transformer is running on

half

> it's designed voltage this terminal is now at 115V. As long as you

don't

> draw too much power (say less than 200W) this is perfectly safe.
>
> There are some suitable smoothing capacitors and bridge rectifiers

in

> the control cabinet (use at least two of the 200V capacitors). The

end

> result is a very solid power supply that works really well.
>
> You can fit all the control electronics and the computer into the

power

> cabinet but you do need to find a compact computer case as it is a

tight

> fit. In my case I moved the power cabinet to the side and scrapped

the

> control cabinet. As you cut the stepper wires this may be a good

idea

> for you to do. If you cut the wires close to the cabinet they

should

> still be long enough.
>
> Les
>

I considered doing this with mine, but decided against it. The 110V
transformer is rated, I believe, about 1KVA but should be derated by
50% if used at half design voltage, so 500VA will be available. I
planned to have a 4th axis provision from the beginning, so reckoned
this wasn't enough. I went for a new toroidal 1500VA transformer
(http://www.airlinktransformers.com/toroids.htm), with 45-50-55V
secondary, to run Gecko 201s, I've only used the 45V tap up to now,it
seems to be quite adequate. Our mains voltage is generally over 240V,
so I'm getting around 48V AC.
I slipped up in not realising the coolant & lub pumps were 110V, I
would have ordered a split primary to run as an autotransformer for
these, much as Les describes. Luckily I had a 110V 100VA transformer
kicking about the place which runs those OK.
I decided part way along the project to give Deskcnc a try, its
controller card need 8 to 20V DC. For this, I wound a tertiary
winding
on the toroidal which rectified gives 13V DC. This voltage will vary
with the secondary load (it's wound over the secondary) but the
deskcnc card incorporates its own regulation & the system works fine.
I scrapped both the Bridgeport boxes, & have the controller/ power
supply in a small enclosure from a cold room control. The computer is
a laptop which I intend to mount on an old Bridgeport DRO arm.
I'm running the spindle motor from an inverter (VFD) which is in a
separate enclosure with the little 110V transformer, so the whole
machine is run from two 13A sockets on the 240V single phase supply.
I bought two of the 1500VA toroidals, and two 64000 uF capacitors,
the
spare ones are available for sale in the UK (bettter prices for two
than one!)

Tim