(PROBLEM SOLVED) PM940 CNC VFD spindle question

I need a little clarification before I screw something up. Including myself. Attached is my voltmeter which i set to measure ac voltage range for 220v. It's set to 500. Is this correct? Also, am i testing the 2 red wires at the far left of the VFD in photo 10? I assume that I ground the black probe and then make contact with the red probe in either the 2 red contact points to get a reading?

If i am wrong, please tell me in detail how to do it. Thank you in advance.
 
I need a little clarification before I screw something up. Including myself. Attached is my voltmeter which i set to measure ac voltage range for 220v. It's set to 500. Is this correct? Also, am i testing the 2 red wires at the far left of the VFD in photo 10? I assume that I ground the black probe and then make contact with the red probe in either the 2 red contact points to get a reading?

If i am wrong, please tell me in detail how to do it. Thank you in advance.
 
I am sorry Rod, I assumed you had a little more of an electrical background. Yes, always be safe. If you are not for sure then ask. So for the input power and the lines to the motor we are measuring AC voltage not DC. So the meter should be set to 500 VAC. The smaller terminals all have low voltage DC at them. So you would use the DC scales and the voltages we are trying to measure are under 25 volts. The Voltages at the Relays inputs (coils) will most likely be 24 VAC or 60VAC so a 100 volt AC scale would be safe. The output from a relay can be what ever is presented to its input.
For AC measurements there is no difference between the black and the red lead. For DC measurements if red lead should be plugged into the red hole (+) and the black lead into the black hole(-). Then when one connects the red lead to a positive DC voltage he gets a positive reading. (what kind of VOM do you have? Is it a DVM or an old fashioned needle style?)

So let me see if I have this correct. I have gotten a little lost in the process. So let me set up some steps.

1) When the computer is turned off, but the Mill power switch is on does the VFD LED display light up? (yes or no)

2) If yes, there is power to the VFD. But you could still measure the inputs to the VFD to see if the power is of quality. I assume you are running with a house hold circuit of 220 Volts 1 phase. If so, then you should set the meter to 500 Volt AC and measure between terminals R and S (L1 and L2) on the VFD. If you do not measure round 220 volts then the power is poor and might not run a motor.

3) If the VFD is on and the 220 input is good, then look at the VFD and see if there is a light on that says FW. If so, then it is telling us that there is an input signal at the MI1 control input, but lets check. Put the VOM meter on a DC scale to check for at least 24 volts DC and then connect the Red lead on the KA1 input which is the MI1 VFD control screw terminal while putting the black lead on the terminal called DCM (page 2-2 of VFD manual) which I think is the wire labeled (111) . You should read 24 volt DC or about this amount. If so the KA1 is working ok.

4) Assuming the power is of quality, and the VFD is displays are working then we need to check the control signals when Mach3 is controlling things. For this we have to turn on the computer and run Mach3.

( will continue while you confirm the above)
 
B2 said:
I am sorry Rod, I assumed you had a little more of an electrical background. Yes, always be safe. If you are not for sure then ask. So for the input power and the lines to the motor we are measuring AC voltage not DC. So the meter should be set to 500 VAC. The smaller terminals all have low voltage DC at them. So you would use the DC scales and the voltages we are trying to measure are under 25 volts. The Voltages at the Relays inputs (coils) will most likely be 24 VAC or 60VAC so a 100 volt AC scale would be safe. The output from a relay can be what ever is presented to its input.
For AC measurements there is no difference between the black and the red lead. For DC measurements if red lead should be plugged into the red hole (+) and the black lead into the black hole(-). Then when one connects the red lead to a positive DC voltage he gets a positive reading. (what kind of VOM do you have? Is it a DVM or an old fashioned needle style?)

So let me see if I have this correct. I have gotten a little lost in the process. So let me set up some steps.

1) When the computer is turned off, but the Mill power switch is on does the VFD LED display light up? (yes or no)

2) If yes, there is power to the VFD. But you could still measure the inputs to the VFD to see if the power is of quality. I assume you are running with a house hold circuit of 220 Volts 1 phase. If so, then you should set the meter to 500 Volt AC and measure between terminals R and S (L1 and L2) on the VFD. If you do not measure round 220 volts then the power is poor and might not run a motor.

3) If the VFD is on and the 220 input is good, then look at the VFD and see if there is a light on that says FW. If so, then it is telling us that there is an input signal at the MI1 control input, but lets check. Put the VOM meter on a DC scale to check for at least 24 volts DC and then connect the Red lead on the KA1 input which is the MI1 VFD control screw terminal while putting the black lead on the terminal called DCM (page 2-2 of VFD manual) which I think is the wire labeled (111) . You should read 24 volt DC or about this amount. If so the KA1 is working ok.

4) Assuming the power is of quality, and the VFD is displays are working then we need to check the control signals when Mach3 is controlling things. For this we have to turn on the computer and run Mach3.

( will continue while you confirm the above)
Click to expand...
I like the step by step in instructions. Thank you.
With the computer OFF and the mill switched on, the VFD does NOT light up.
I know the mill is getting power as I can move all 3 axis controlled by Mach3

Whats next?
 
4) Assuming the power is of quality, and the VFD is displays are working then we need to check the control signals when Mach3 is controlling things. For this we have to turn on the computer and run Mach3. Make sure on Mach3 that the nMotion is connected. Confirm the the spindle button is set for Forward (CW) motion. Set the spindle speed to about half, 500, and then click the spindle button. I assume the motor does not run. Look at the VFD LED display and see what it says. See if the FW LED next to to the LED key pad display is on. Reconfirm that the VFD MI1 is active (24 Volts DC). If all of these are true, but the motor is not running then lets check the speed signal coming from the n-Motion. Set the VOM to measure up to 10 volts DC. Put the red lead (+) on to the terminal with the yellow wire it should be the PWM terminal at the N-motion and the small yellow wire at the VFD (terminal 081 I think) while putting the black VOM lead on the VFD terminal with the small red wire, (079 I think) which comes from the n-motion EGND terminal.

You should have a reading of about 5 volts DC. If not, repeat the last measurement at the n-motion terminals to see if the n-motion box is sending out a signal at all. If this signal is not at the n-motion then the problem is with the n-motion or the computer connection. If there is a signal at the n-motion but not at the VFD terminals then there is a wire problem between the two. If the signal is at the VFD and the KA1 signal (MI1) is present then there is a problem at the VFD or the motor.

We can proceed from here after we know the answers from these measurements.

Dave.
 
VFD does not light up! Was the Line power getting to the VFD. VOM on 500 VAC setting measure between R (L1) and S(L2) VFD terminals.
 
B2 said:
VFD does not light up! Was the Line power getting to the VFD. VOM on 500 VAC setting measure between R (L1) and S(L2) VFD terminals.
Click to expand...
This is my meter and set to 500 vac. As far as measuring current, Do I simply touch the red probe individually on the contact to the R(L1) and S(L2) terminals, which are the 2 red wires on the far left of the bus bar in the attached photo? How and where do I ground the black probe from the meter? Sorry for the very basic questions.
 

Attachments

  • multimeter set to ac.jpg
    multimeter set to ac.jpg
    136.8 KB · Views: 78
  • pm940 cnc 7.jpg
    pm940 cnc 7.jpg
    106.4 KB · Views: 75
The meter leads are connected correctly. The dia is set to 500VAC which is correct for measuring the power. We are measuring voltage not current. The connections you want to connect to are not on this terminal strip, which is shown in this photo. The photo shows the low voltage control signals not the power. Look at the VFD manual page 1-3 which shows where the big screw terminals are for the input power at the TOP of the VFD, above the key pad. The power wires should be connected to R(L1) and S(L2). Put one meter lead on R of these and the other meter lead on the S. The meter should show about 220 Volt AC. Just in case there is a problem here, turn off the power to the box and make sure the screws holding these wires are tight. I think the cover for these leads comes off if you want to look to see if a wire to the VFD is broken or loose. Other wise you can do the measurement by sticking the VOM leads points through the plastic holes to the screw terminals.
 
The covers to these terminals as well as the ones to the motor at the bottom of the VFD fold down to allow you to look at them. See VFD manual page 1-8.
 
B2 said:
The meter leads are connected correctly. The dia is set to 500VAC which is correct for measuring the power. We are measuring voltage not current. The connections you want to connect to are not on this terminal strip, which is shown in this photo. The photo shows the low voltage control signals not the power. Look at the VFD manual page 1-3 which shows where the big screw terminals are for the input power at the TOP of the VFD, above the key pad. The power wires should be connected to R(L1) and S(L2). Put one meter lead on R of these and the other meter lead on the S. The meter should show about 220 Volt AC. Just in case there is a problem here, turn off the power to the box and make sure the screws holding these wires are tight. I think the cover for these leads comes off if you want to look to see if a wire to the VFD is broken or loose. Other wise you can do the measurement by sticking the VOM leads points through the plastic holes to the screw terminals.
Click to expand...
Dave, we are making progress! I appreciate the detailed instructions as it gives me confidence. The L1 and L2 were easy to locate behind a cover plate and well exposed. Both contacts were easily accessible with the 2 probes. Zero reading on the multi-meter.
 
You must log in or register to reply here.
Back
Top