Worth Upgrading To Inveter Rated Motor 1340gt?

unless you are continuously operating above 90 hz or below 30 hz, you will gain little to no advantage by purchasing an inverter rated motor.
 
unless you are continuously operating above 90 hz or below 30 hz, you will gain little to no advantage by purchasing an inverter rated motor.
If his purpose is to avoid making speed changes with his gearbox, then there would be an advantage. If he is just going to adjust it up or down a few Hz to get an exact rpm, then not much advantage.
 
If his purpose is to avoid making speed changes with his gearbox, then there would be an advantage. If he is just going to adjust it up or down a few Hz to get an exact rpm, then not much advantage.
i think you missed my point, we have already established that the motor will be vairiable speed.
my point is that it is not necessary to spend the extra $$$ to get an inverter rated motor UNLESS He'll be operating under 30 hz or over 90 hz continuously
 
Agree with Ulma Doctor, the main advantage is a wider speed range, traditional 3 phase motor's performance tend to drop off above/below this range, although sensorless vector as opposed to V/Hz VFD setting allows you to go lower with little performance loss of torque (Hp drops off in a linear fashion below the base frequency). Most newer 3 phase motors are rated for use with VFDs, and have a constant torque ratio of around 10:1 so they should be good to 6Hz with sensorless vector http://www.marathonelectric.com/docs/017-020VariableSpeedInfo.pdf . It is still not wise to operate a TEFC motor below 30 Hz for any extended amount of time because of cooling issues, 30-90Hz is a reasonably acceptable range for this application.

There are various versions of "inverter rated motors" some have insulation that are more tolerant of inverters, others are of the "vector" type that are designed to work over a very wide speed envelope. These typical inverter/vector motor have CT ratios of 1000:1 or greater, so full torque down to around 0 RPM and maintain full Hp up to 2X their base speed in the 1-5 Hp range. You can also jack up the short term overload parameters on these motors. The main advantage is the the higher (and lower) maximum speeds, you do not need to do a belt change if this is part of the equation, if single belt speed than this is moot. By spinning the motor over 60 Hz, you are delivering more Hp to the spindle, and approximately the same torque, relative to a fixed speed motor that is geared up for the spindle speed. This is calculating the applied spindle parameters when you account for the gearing ratio changes required of a fixed frequency motor.

Bottom line, the stock motor on the PM1340GT works very well, I was never able to not have enough power or see any appreciable speed change with it with the WJ200 VFD. The inverter/vector motor did allowed me to not have to deal with belt changes and operate the speed range routinely from 15-120 Hz on the fly. Essentially I use two gears H and L in the headstock gearbox for general speed ranges, there is no issues with cooling, it stops frighteningly fast to the same exact position with an electronic stop.

On pulleys, I really have not seen an issue. I use a Maska pulley which is a Baldor brand (they are made in different countries) but seem to be well made.
 
i think you missed my point, we have already established that the motor will be vairiable speed.
my point is that it is not necessary to spend the extra $$$ to get an inverter rated motor UNLESS He'll be operating under 30 hz or over 90 hz continuously

And I think you missed any point as well. I was agreeing with you.

If he keeps using the gear box to change speeds and only adjusts a little with the VFD, go with the non-inverter duty motor. If he wants to adjust speed solely with the VFD (i.e. 20 Hz up to 120 Hz), not the gear box, get the inverter duty motor.
 
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