Re: [CAD_CAM_EDM_DRO] Horsepower rating
Posted by
Bob Campbell
on 2000-03-14 17:59:05 UTC
Tom,
When you are running with higher voltage, how do you specify the size of the
transformer. I will be using some new 3 phase stepper motors that will run
at 130 volts at 5 amps. I bought a 2 KVA 15 amp transformer at 90 VAC (130
Volts peak DC). The transformer also has a 17 VAC winding for a 24 volt
power supply. I would like to use a smaller (lighter weight) transformer.
Bob Campbell
When you are running with higher voltage, how do you specify the size of the
transformer. I will be using some new 3 phase stepper motors that will run
at 130 volts at 5 amps. I bought a 2 KVA 15 amp transformer at 90 VAC (130
Volts peak DC). The transformer also has a 17 VAC winding for a 24 volt
power supply. I would like to use a smaller (lighter weight) transformer.
Bob Campbell
----- Original Message -----
From: tommy marantz <tommym6@...>
To: <CAD_CAM_EDM_DRO@onelist.com>
Sent: Tuesday, March 14, 2000 2:56 PM
Subject: [CAD_CAM_EDM_DRO] Horsepower rating
> From: "tommy marantz" <tommym6@...>
>
> De lurking for a bit,
>
> Many commercial stepper motors can produce suprising peak (but real) HP.
My
> old Sigma catalog shows peak hp at about 1.2 @ 10,000 steps per sec. for
> some 4.2"d x 8"l models. This was using a 90V drive.
>
> The purpose of the high voltage drive is to overcome the motors inductance
> so it will step (run) fast. The motor is not absobing the full 90V at 13A
> per phase. The average phase current is lower since it spends time
ramping
> up and ramping down.
>
> A good drive will get the current up to full rating way before the next
> step, so higher voltage is better in this sense. At full current, you get
> full torque. spend time ramping current, you get less torque.
>
> Get high torques at higher speed, you get higher HP.
>
> The HP of course does not come for free and motors are not 100% efficient,
> special steppers have claimed 80% efficiency vs standard types that get
40%.
> Ideally 1HP = 750 Watts.
>
> Hope this helps
> Tom
>
> >I have a hard time seeing 90 V @13.2 A per phase (x2) = 3.19 hp.
> >The motor is smaller than a 3/4 hp induction or synchronous
>motor...could
> >the above numbers be 'peak hp', like
> >vacuum cleaners specify?
>
> >Something doesn't add up for me.
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