Need motor experts

[CH(upstate,NY)]

Been 30 years since I got my BSEE and I haven't had to design a motor since then. I've got a Delta 50-850 dust collection system, 1 1/2 hp TEFC motor. I was between cutting when I heard the motor wind down and the breaker in the main panel trip. The motor is free. If I reset it it will try to start but after a few seconds either trip it's protection breaker or the 20 amp one in the panel. It's the only load on a 20 amp circuit.

Does anyone have any quick ideas before I get my DVM out? I'm trying to get new cabinates and benches built in my new cabinate shop set up and don't want to waste alot time.

By the way, Happy Easter guys.

 

[Anonymous-0]

Is it possible that the motor is wired for 220vac and you are running it on 120vac?

 

[El Toro]

What's the max amp rating on the motor & voltage? Hal

 

[CH(upstate,NY)]

Neither. It's running on 120v. When I get the duct work in I was going to rewire it for 220. There's no problem with the power it's getting. It's been running this way for a couple of years, although it's been sitting while I've been building. I've run it for a couple of hours since I moved it to the new shop. Again, I know power is not a problem.

The moror will start turning but not get up to speed before it cuts out. Gets warm on the way.

Again, it's not that old.

 

[TractormanNC]

Check the starting capacitor and starting switch(the one inside the motor that disconnects the starting cap)
Leonard (also a BSEE)

 

[El Toro]

Have you tried it on another breaker? Hal

 

[Anonymous-0]

the magnets are sticking in the motor need oil and a cleaning out

 

[dave guest]

If it's a universal motor with brushes, high speed like a vacuum and the brushes are burned you probably have open winding in armature. Also if you see ring of fire around commutator. Check motor amps with clamp on ammeter, also to confirm.

 

[dave guest]

If it's a universal motor with brushes, high speed like a vacuum and the brushes are burned you probably have open winding in armature. Also if you see ring of fire around commutator. Check motor amps with clamp on ammeter, also to confirm.

 

[Kentb of SWMO]

Motor has ean for a few years as now wire. Was runnig and heard to slow down and trip the circuit breaker. This is easy. The motor died. Replace motor.

Kent

 

[Anonymous-0]

I believe you said a 1 1/2 HP Mtr @ 115 Volts AC. If thats the case, The full load amps (fla) is somewhere in the range of 16.4 to 19.6 fla. A 20 ampere circuit breaker (CB) CANNOT carry that much current without damage after a few starts - maby 40 max. Conclusion: most likely a damaged/bad breaker. You should be using #10 Copper wire and a 30 ampere safety switch or a motor starter as the starting current is 5 to 6 times the fla.until the motor is up to speed. CONTACTS in a 20 or 30 amp (same) are NOT rated for motor starting.Odds are thats the problem ,but it could be a starting winding/ unlikely..SUGGESTION: Rewire motor connections in the mtr box for 220 volt operation, and install a 30 amp / 250 volt fusible safety disconnect switch with (2) 15amp dual element fuses( FRN-R15)&use switch to start/run mtr.At 240 volts the current is 1/2 the 120v rating . You will not burn out your motor PERIOD. Check the NAMEPLATE for your mtr fla at the voltage you use, and size the DE fuse at 150% of mtr.fla...?'S contact me..

 

[CH(upstate,NY)]

Plate reads " 120/240v 12/6 amps" I know you have an inrush to start the motor but I think a 20 amp circuit would handle it.

I'm going to wire it for 220 tonight. When I wired my shop I installed 4 220/30 amp and 2 220/50 amp circuits.

The replacement motor costs $380. I'd like to avoid that.

 

[CH(upstate,NY)]

yep

 

[Anonymous-0]

Can you measure your motor current? Does the motor have a capacitor mounted on the motor? does the motor have a machenical start switch internally? (would be a bit rare on this size motor) or externally? I would guess its a standard induction motor? It might also be a series wound motor with brushes?,(not usually in a TEFC type motor) It was late when I glance at the motor current tables,sorry must have read the wrong current (flc). Breaker comment still apply, but what brand/ type are in your panel? HOPE NOT TOO MANY ?'s , just trying to help

 

[CH(upstate,NY)]

Phil, The plate says Delta Machinery. It got a cast case with the raised ribs heat sinking)? It has a control box on the side with the start and stop buttons, circuit breaker button and a 200ufd/ 125 v starting cap. The is also a 30ufd/250 volt cap straped under a cover on the other side. I removed the fan cover and there is what looks like 1 mechanical contact. As you spin the fan, it looks like there is a wavy washer that oscillates the contact but not enough to break contact. The assembly has a couple little coil springs. Looks like some kind of inertia (bad spelling) device. Never seen this kind of setup. As far as power, it's the only thing running off a 200 amp entrance.

Square D breakers. Don't own a current probe. Seems like it's not switching from start to run. I've had it 6 years but I doubt it has 10 hrs. on it. Worked great while I cut panels out of 10 sheets of plywood. Was on seperate circuit from my saw.

 

[buickanddeere]

I agree. Stuck centrifical starting switch or open start capacitor(s).
Breaker is too small as well. People never seem to learn that a breaker or fuse is short circuit protection.
Overload protection is provided via a thermal element in the motor starter or junction box.

 

[Anonymous-0]

I believe from what you say that the problem is in the starting mechanisam or the start capacitor(200mf). To trouble shoot #1 TURN ALL POWER OFF and check to see that it is off with DVM. #2 isolate or remove one wire from the 200mf Cap. and use your DVM on its highest ohm scale and measure thr Resistance. The meter scale should slowly rise to a very high (infinity) reading. If it does not increase smoothly to max reading it is bad.(Easier to see on analog meter) This is testing it at a much lower voltage then normal, but its pretty reliable. My guess is a 50% chance. The other most probable prob. is the centrifical start mech. Look for the obvious 1st: dust in moving parts, burned or pitted contacts,broken/loose springs, see if the wobble washer is free on mtr shaft & if you can operate it by hand to open switch. Its also a good idea to look for the obvious like a loose connection- broken wire etc.#3rd perhaps wiring diagram in cover or maby you can determine which is the 2 wires to the starting winding, check on low ohm scale the resist of winding and on the highest ohm scale of each wire to the mtr enclosure for a fault to ground. Let me know what developes. Hoosier greetings & GOOD LUCK

 

[d. coleman]

i have the exact delta blower/vac. and had the exact same problem. copasiter change fixed the problem also check for vane blockage, or a pluged hose or housing. good luck, d. coleman