# My Wiring Saga Continues  Teco Fm50 Vfd Expert Needed



## Wheresmywrench? (Jun 20, 2015)

I have a new TECO FM50 1hp VFD that I will be programing to use external switching to run my Emco Maximat 10-P Mentor lathe/mill. This way I'll be able to use the forward and reverse switches on my panel. And my safety switches still work. I will use the main power switch to supply power to two VFD's, 1 for the Mill Head and 1 for the lathe. 
The reason I have two VFD's is that the 220V single phase motor I bought turned out to be a 3phase motor with 2 bad sections. So had it rewound $228 and the motor cost $150.
So my power goes from the panel main switch to the VFD's. I'll have a +12V wire from the VFD that runs to the rotary switch then two wires running back to the VFD, one for forward and one for reverse. With this set up I just turn on the main switch, turn on the VFD then switch the forward/reverse to the desired direction I want to run the lathe. I have two other external connection points one I plan to use for a jog feature.
I was thinking of using the other spare connection point to switch from low power to high power wiring on the two speed motor. Now in order to use the low speed I would have to wire in two tier contact with a normally open and normally closed set of contacts as the 1 2 & 3 wires from the motor need to be joined when running high speed. And open in low speed. Will this work without affecting any of the programed settings of the FM50? Any ideas?  

Reguards


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## aeroHAWK (Jun 20, 2015)

If you could provide a schematic, it would be much less confusing.  But it sounds like you want to put some kind of switch between the motor and the VFD. That is a DEFINITE NO-NO!

If you want two speed operation, the VFD will provide that, without the need to switch motor leads. Also, the VFD can provide much more in speed control options.


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## AJB (Jun 22, 2015)

I hooked up a TECO JNEV on a lathe not long ago and found it to be fairly easy.  Hook the 3 phase power directly to the motor and run small gauge wires to your control panel.  You will need three wires for Forward/stop/reverse and three wires for speed control.  You can add a couple more control options if you want such as jog and EStop.  For the optional controls you only need one wire each from the VFD and the second wire for these controls is a jumper wire from the F/S/R switch.

After wiring in the controls you will need to do some parameter changes that are also pretty simple.


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## mwooten (Jun 22, 2015)

2 speed motors such as you have are for use with multiple contractors. Low speed T1, T2, T3 and High speed T11, T12, T13.  I would suggest wiring the low speed to the VFD and capping off the high.  Again, do NOT wire anything between the  motor and VFD..


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## Wheresmywrench? (Jun 22, 2015)

I have it wired up and have also wired it for Forward/Stop/Reverse and added a jog button. I know you are not supposed to have anything between the VFD and the motor. But you can as long as you DO NOT switch the contacts. I have not done this. But you can idiot proof the machine by making sure there is no power to the VFD until after the speed has been selected. I do know a fellow who has the same machine as I do and he runs it with the VFD, same one I have, between the power supply and the machine. Using ALL the machine switches with no problems.


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## mksj (Jun 22, 2015)

Anything is possible, and as you mentioned, you can switch the VFD motor wires with the VFD not running. On the other hand there is probably no reason to use 2 speeds of the motor, because in essence the VFD does the same thing. It will provide constant torque below its base speed, and constant horsepower above the motor base speed assuming this is at 60Hz. A 2 speed motor can be wired in different configurations, so it is a bit difficult to say if the low speed or high speed configuration is the best option to run off the VFD and the Hp/Torque ratings. Two speed motors are usually designed to provide either constant torque or constant horsepower, I assume yours is set-up for the former which is exactly what the VFD will provide below the motor base speed (and probably do it better in a sensorless vector configuration). Another concern would be that VFDs are setup based on the motor specifications, poles, base RPM, Hz, voltage and some include winding resistance. These can be very different between the low speed and high speed wiring configuration of the three phase motor, so the overload point setting might not be optimized for both configurations and this might lead to motor damage in an overload situation. Others with more experience with two speed motors and your specific motor wiring configurations could probably direct you as too which would be optimum for your usage.


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## Wheresmywrench? (Jun 22, 2015)

Yes it is 60Hz motor. It's of European origin but I just had it rewired and that was done to North American standards. And yes it has been rewired to give constant torque. We have it wired for high speed and will use the VFD for speed control. I am using the VFD's external connection capabilities to utilize my panel controls for Forward/Stop/Reverse. I have also added a Jog button to the VFD. Speed will be controlled with a pot that I ordered for this particular VFD.


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## aeroHAWK (Jun 22, 2015)

I don't understand why you would include in your title "*Teco FM50 VFD Expert Needed*" and post the question "*Any ideas?*" and then totally disregard the great advise and guidance provided by those that respond!


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## mwooten (Jun 22, 2015)

Typically there is an overload for each the low and high speed based on the nameplate current for the two speeds.  Most of the motors I've dealt with were constant HP.  That is why I suggested using the low speed.  Yours may be different.    Still I would guess the low speed windings at 120 hz or so would be plenty fast enough


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## Wheresmywrench? (Jun 22, 2015)

No ones input was ignored, it looked at and considered. Also NO contacts  after the VFD is an industry statement to cover the manufacture if a VFD is damaged by doing so. You can run all kinds of switches after the VFD as long as they are switched before the VFD is started. why would I run in slow speed at 120Hz when High speed at 60Hz is recommended? Driving the motor at 120Hz will damage it as this is beyond its designed capabilities.


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## mksj (Jun 22, 2015)

Wheresmywrench? said:


> Also NO contacts after the VFD is an industry statement to cover the manufacture if a VFD is damaged by doing so


Agreed.  It is probably more precautionary, and this subject has been discussed extensively in a previous thread(s). I believe there are varied suggestions based on incomplete information on the motor specifics, type, age, wiring configuration, etc. There are probably different recommended connection configurations depending on the motor and VFD combination. If you had a standard single speed 3 phase inverter rated motor, a 4 pole motor, it should be capable of running at 120Hz without problems. Each manufacturer has there own recommendations, but I did call several of them a while back and the usual was 2X the base speed for a 4 pole. But performance characteristics may deteriorate in a non-linear fashion above ~90-100Hz unless the motor specs specifically states otherwise (usually vector motors). Most of my 3 phase inverter/vector motors run and are rated to 120Hz. You're motor most likely does not fall into this category, so something like 90Hz might be the maximum, and that assumes you need that speed. If you are running constant torque, then you would most likely use the higher RPM speed wiring and the VFD would provide constant torque below the base speed. 

The major concern as previously outlined is matching the motor characteristics to the low or high speed connection configuration of the motor. I have no experience in this area, so will differ to others as to what might be best for you, or you can experiment and see what gives the best performance. In theory the more elaborate VFDs have configuration for 2 motors, one could program a set of variables for the low and high speed connections.


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## mwooten (Jun 23, 2015)

If the motor is not designed for variable frequency probably should not install one.


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