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Ceengland
Joined: 11 Oct 2020
Posts: 393
Location: MS
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 Posted: Mon Jan 04, 2021 2:50 pm Post subject: Any ideas where to get electric motor brushes? |
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On 1/4/2021 4:11 PM, rparigoris wrote:
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Hi Bob It's for a 1941 Monarch EE. It has a 5HP 3 phase AC motor that spins a 4 pole DC generator, the generator is connected to a 2 pole exciter and the DC motor is 4 pole. In 1941 they didn't know how to speed control an AC motor so they did so with a DC motor. I forget exactly the hocus pocus they are doing, it doesn't have a huge tube, but slow speed torque is quite impressive. I need exciter and generator brushes and will probably change the motor brushes as well. All 3 devices have shunt wires. How do I determine what hardness I might want? The exciter brush has 600 on it. The generator brush has 063A on it. I have a call into Monarch, but my generator and exciter may not be stock. Thx. Ron P.
I'm not Bob, but that sounds like a basic rotary phase converter; still
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available to get 3 phase power from 'single phase' service. Might be
branded/made by Monarch, or sourced from a vendor that makes motors &
phase converters. Is the rotary converter built into the lathe, or a
separate component? The ones I've seen are typically separate from the
tool, and often are used to power more than one 3phase tool in the shop
(sometimes one-at-a-time, depending on converter capacity). If it's a
separate component, it should have a dataplate on it somewhere.
FWIW, solid state converters are relatively cheap these days; ex:
https://www.amazon.com/Digital-Phase-Converter-5HP-Range/dp/B07F243HLG/ref=psdc_10967761_t1_B00FF1S5IS
And if you shop around a bit, you can find a 'variable frequency drive'
that will not only give you 3 phase, but the ability to vary the rpm of
the lathe using the converter. Like this:
https://www.amazon.com/Single-Phase-Variable-Frequency-Inverter-Controller/dp/B07L8XZFYG
And no more brush worries (at least in the converter).
Charlie
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rparigoris
Joined: 24 Nov 2009
Posts: 805
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| Posted: Mon Jan 04, 2021 5:17 pm Post subject: Re: Any ideas where to get electric motor brushes? |
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Hi Charlie
My Monarch EE helped to win WW2. It was owned by the Singer Corporation until the 1970s. Back in the day, 3 phase AC motors couldn't be speed controlled. Thus Monarch has an integral 3 phase AC motor with DC Generator. At the tip of the spinning mass is an Exicter. Some Monarch also used a Magnetron tube. The idea was you could have a variable speed on the fly with good low speed torque. If you just cut voltage on a DC motor you can speed control it but low speed torque suffers. Monarch does some hocus pocus that increases torque at lower speeds compared to just cutting voltage. DC motor has 4 brushes. Today you have PWM speed controls for DC motors which can do the same thing, but back then this was a terrific desirable feature. There are many Monarchs that modify the unit by removing all this stuff and associated relays and controls and replace it with a brushless 3 phase AC motor with a speed controller. Not a trivial modification.
I power my stuff with a 7.5hp rotophase running on 220v single phase including the Monarch.
The main DC motor was rebuilt early on but the Exciter and AC/DC Generator is what was with machine when purchased from Singer.
I actually have 2 rotophase converters. One 3hp and one 7.5hp. Since the late 1970s all that I did with the Rotophase converters is put in a tiny amount of grease and replaced relays and capacitors perhaps once each.
I remember replacing all the brushes in the 1980s when I was using the machine alot. I got them from the motor rebuilder. Brushes have lasted till now. Ron P.
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