RF 30 clone with bad motor. You have me convinced to go with a 3 phase motor and vfd. I hope to find a used motor but I need some help in what to be looking for. Should I be looking for 2 or 3 hp, some motors are 2 pole and some are 4 pole ? Shaft size on 3hp motors tends to be 1.125, would definitely need a new sheave for that and I was kinda hoping to reuse the original one. How about rpm? Anything else that I should be aware of? After I source a motor I’ll start my search for the vfd. Thanks, Bart
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Motor upgrade help
- Thread starter bfi
- Start date
- Joined
- Feb 2, 2013
- Messages
- 4,086
A 1750 rpm, 2Hp motor would be sufficient
NEMA 56 frame motors have a 5/8” shaft, with the exception of the 56HZ frame has a 7/8” shaft .
They are generally 9 wire motors.
NEMA 145TC frame motors have a 7/8” shaft
The 184 frame has a 1-1/8” shaft
An inverter rated motor is best for extended use in low or high frequency conditions.
A non-inverter rated motor can be operated in the 30Hz to 90Hz envelope for short periods of time without appreciable consequence .
I have not experienced any failures on non-inverter rated motors following the practice.
Some will try to convince that you have to get a specific brand of inverter or spend more than you have to, but i’m here to say that you can run inexpensive vfd’s .
I’ve tested and worked with many different brands, from dirt cheap to high end drives.
There’s one thing that they all share, the possibility of failure. $1,800.00 drives fail too- i had to replace one today in my regular job for a grocery store in a meat portioning machine .
I replaced the inverter with the OEM Lenze drive.
If you aren’t in a production environment or making money from your mill, then a cheap drive is more cost effective.
NEMA 56 frame motors have a 5/8” shaft, with the exception of the 56HZ frame has a 7/8” shaft .
They are generally 9 wire motors.
NEMA 145TC frame motors have a 7/8” shaft
The 184 frame has a 1-1/8” shaft
An inverter rated motor is best for extended use in low or high frequency conditions.
A non-inverter rated motor can be operated in the 30Hz to 90Hz envelope for short periods of time without appreciable consequence .
I have not experienced any failures on non-inverter rated motors following the practice.
Some will try to convince that you have to get a specific brand of inverter or spend more than you have to, but i’m here to say that you can run inexpensive vfd’s .
I’ve tested and worked with many different brands, from dirt cheap to high end drives.
There’s one thing that they all share, the possibility of failure. $1,800.00 drives fail too- i had to replace one today in my regular job for a grocery store in a meat portioning machine .
I replaced the inverter with the OEM Lenze drive.
If you aren’t in a production environment or making money from your mill, then a cheap drive is more cost effective.
- Joined
- Apr 30, 2015
- Messages
- 12,414
2 HP is plenty for a small milling machine like that
- Joined
- Oct 13, 2014
- Messages
- 10,302
You want a 4 pole motor which will give you 1,725-1,800 rpm. A 2 pole motor will be twice as fast 3,450-3,600 rpm, too fast for a mill. The slower 4 pole motor will deliver more torque.
- Joined
- Feb 2, 2013
- Messages
- 4,086
Shaft lengths are pretty standard to the motor frame designation, unless you’re talking about pump duty motors, then the shaft lengths and features are diverse
