Leeson 90 VDC motor controller experience?

We use many Leeson model M1740007 90 VDC motor controllers BUT are experiencing what seems to me to be high failure rate.
Ratings
max armature amps 1.5
HP range 1/20 to 1/8

Some of this is just the fact that nothing lasts forever including solid state. Some of the problem is probably water in unit (food industry and washdown).

Some of the problem may be that we merely turn off the supply power to stop a motor. The manual says not to do this frequently use the inhibit or dynamic braking to stop.

Some of the problem is technician error - I wont say who but I hit the reverse switch while it was running.

Motor was 1/15 HP and was drawing approx 0.25 amp.
When I did this the current limit LED lit, the speed control pot had no effect, output voltage maxed out to about 136 volt and no ability to reduce it. A new unit had about 108 VDC out no current limit light and speed pot was just fine and had good control of output voltage. So I conclude I just broke the voltage control and the unit is trash.

I would like to know if there is a hardier unit ie more tolerant of dumb mistakes and better able to handle harsh environment.

Dan Bentler

There is Dart http://www.dartcontrols.com/products3.asp?Product=250G

KB has units designed for washdown environments, look at the 240D
http://www.kbelectronics.com/catalog_nema_4x.htm

Oh, Grainger has Dayton line that also have Nema4/12 http://www.grainger.com/Grainger/categories/motors-and-power-transmission/motor-supplies/dc-speed-controls

leitmotif said:

Some of the problem may be that we merely turn off the supply power to stop a motor. The manual says not to do this frequently use the inhibit or dynamic braking to stop.

Click to expand...

Dan, I have had some hands on experence with the Dart unit that Ron's link points to. The dart units use an ordinary dpst toggle switch to interupt the incoming power. This is the factory setup for dart. Perhaps they would be a better fit because of this.

You can buy a tougher drive, Dan, but the plug reversing of the motor needs to stop. That's a fast way to demagnetize the motor field magnet and then, of course, even if the drive survives, the motor is toast.

Dick,
That was a dumb mistake. I don't do plug reversing except on cranes and forklifts that are designed for it. Motor seemed OK after my foopah.

Any recommended drives??

Dan

I like KB but I don't know of any that are "bad".

Have done a little reading based on the referances you folks have given me. Thank you Mr Doran and others.

I see that the DC controllers come in two designs ie SCR and PWM.
Stripping away all the bells and whistles I see they are basically the same but the big difference is I would have a more Pulse DC with SCR than I would have with PWM. PWM would (similar to AC VFDs) have a higher firing rate which would give me a "truer" (less ripple / pulse ?) DC.
The main advantages of PWM would be quieter motors ie less whine and better commutator performance.

While I am at it I know the average Fluke RMS VOM will not give true readings on VFD outputs. Does the same problem exist with the DC controllers both SCR and PWM?? How much error would I have?

Dan Bentler

All meters work just fine with DC SCR drives. The true RMS meters are more accurate with PWM than they are given credit for.

Do you have to stay with a DC drive and motor?