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  1. Barry1961

    Large 8-pole induction motor for slow speed application

    I agree with jraef. Figure out what the actual torque is. You may have a 5000 hp motor doing a 1000 hp job. Barry
  2. Barry1961

    Accelerating a Mass with pneumatics

    A flywheel? Since you will be accelerating faster than gravity you would not need to release only at the bottom of stroke. I was thinking of a punch press design. You may need the ram to quickly reverse stroke and get out of the way of any bounce. Have the down stroke of the ram trigger a...
  3. Barry1961

    Fan cooled motor without fan

    I was hoping that with the low duty cycle would it not be a problem at all. But I have absolutely no real world experience running a TEFC motor without a fan. There should be room enough to mount an external fan if needed. Barry1961
  4. Barry1961

    Fan cooled motor without fan

    The 1/4 hp will be deenergized while the creep motor is running. The creep motor will be deenergized and disengaged, with clutch, when the 1/4 hp is running. Thanks all!! Barry1961
  5. Barry1961

    Fan cooled motor without fan

    I have a .25 hp, 750:1, TEFC integral gearmotor that I want to drive very slowly by removing the fan and coupling to the stub shaft. It would be driven about 6 rpm with another very small integral gearmotor through a small clutch. A basic creep drive. The actual required horsepower at high...
  6. Barry1961

    High cycle DC injection braking

    ozmosis In past applications I did not have much luck generating torque quickly in V/F mode. In a recent application with a Mitsubishi E700 it took about .5 second to reach 100% FLT in V/F mode. I tried raising the voltage boost with not much effect. The way I got torque quickly was in...
  7. Barry1961

    High cycle DC injection braking

    Brother lists the max brake cycles at 10 per minute. From what I understand this is due to the brake coil getting hot from the high inrush. I don't know how much a light spring would improve the rating. Maybe a light spring and a resistor? I have done my best to convince the customer not to...
  8. Barry1961

    High cycle DC injection braking

    Sorry about not putting the VFD in the OP. It is an AB PowerFlex and a Brother gear motor. Brother and Sumitomo both make very strong high reduction, high efficiency gearboxes down to 1/50th hp in 3 ph. They are just single voltage at 1/50th, 230 V or 460 V. I have used these on several...
  9. Barry1961

    High cycle DC injection braking

    It is a vector drive, they are just worried about drift. I don't think they will need it but they like the idea of the rotor being locked in place after decel. There is no feedback now and they don't want to add any. Barry1961
  10. Barry1961

    High cycle DC injection braking

    I really hate to say this but I am not sure how to accurately measure the DC current. I would guess the VFD is still using the same carrier frequency and just turning off most of the IGBTs to get the DC so I need a RMS reading. Will the winding act as a good enough filter to allow a accurate...
  11. Barry1961

    High cycle DC injection braking

    A customer has a small high cycle indexing conveyor with a 1.3 second cycle. Almost all the braking with be done with decel but they are thinking of using DC injection braking to insure the motor comes to a complete stop. This is a 1/50th hp, 3 ph motor on a 300:1 high efficiency gearbox...
  12. Barry1961

    Calculating Motor Torque on VFD

    With the tests done so far the final ratio should be around 240:1 which would more than double the reduction. The load has a fair amount of inertia to overcome during start up so the peak motor torque should drop even more since reflected inertia is divided by the square of the ratio. The cost...
  13. Barry1961

    Calculating Motor Torque on VFD

    The customer was able to get some support from WEG at last. The WEG was displaying amps and not percentage. But the WEG guy says go by the percent torque in sensorless vector mode and it should be within 2-3%. The readings from sensorless vector percent torque seem to be about what I expected...
  14. Barry1961

    Calculating Motor Torque on VFD

    I was told from another source that if I put the VFD in vector mode and read the percent torque parameter it should be fairly accurate even at low hertz. The VFD self tuning would compensate for hertz and voltage variations. He also said you would need to know the VFD output voltage...
  15. Barry1961

    Calculating Motor Torque on VFD

    They are running the motor at 25 hertz now which is the speed they need to run for the application. This is a 4 pole 1769 rpm motor so the motor rpm is going to be close to 725 rpm at 25 hertz. The motor is running cold, at ambient. Barry1961
  16. Barry1961

    Inverter duty

    If this is a positive displacement pump with a 20:1 speed range you will probably use a drive with vector mode torque control. One thing to be aware of with some “inverter duty” motors is that the electrical and mechanical characteristics may not be standard. The motor may be larger than a...
  17. Barry1961

    Calculating Motor Torque on VFD

    A customer has a 10 hp, 480 V, 3 ph, Baldor Motor # CWDM3714T driving a mixer through a 100:1 helical gearbox. The motor is being driven by a WEG VFD in the volts/hertz mode, (not vector) at 25 Hz. The following reading were taken by a old clamp on amp/volt meter, Simpson I think, which does...
  18. Barry1961

    PSC motor reversing at stall

    There will be force trying to back drive the motor when it stalls. If this is enough to overcome the positive locked rotor torque I don't know. But the motor does reverse and runs well enough to do damage. Thanks!! Barry
  19. Barry1961

    PSC motor reversing at stall

    It may be that the current spike is fast enough to be in the range of normal start up current/time over the expected power range. PSC motor are more sensitive to low voltage that other types. PSC motors have a fairly low starting torque/current and are often used in high cycle reversing...
  20. Barry1961

    PSC motor reversing at stall

    The problem is that the motor reverses without the starter reversing. This causes the door to go back up and hit the up end of travel limit switch which does not turn off the down relay. When this happens expensive things break. Most doors reverse when they sense an obstruction on the leading...

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