Dc motors and drives

[quebmaint]

I can see it starting right now. 20 questions and pulling hens teeth.

Please supply the following info
1. Line phases and voltage
2. Nameplate on drive or adequate description of rated line voltage and current. Rated motor type volts and amps
3. Nameplate info on motor OR type of motor as I asked for in #3. Include rated voltage and current, HP and RPM. Sure would be nice to include rated torque
4. Take torque wrench and measure torque at the input of the conveyer ideally the gearbox input shaft.

Dan Bentler

1. 240volts single phase
2 minnark drive 240/120 vac 90/180 vdc 5 hp
3 180 vdc 5 hp 1750 rpm 24.5 fla
4 I had the motor unloaded so I wouldn't think torque would be a factor
Thanks again for everyone's involvement

 

[Lancie1]

4 I had the motor unloaded so . . .

With motor unloaded and getting no drag from the conveyor, will not the regen brake current hit a maximum in a short period of time? Could that be what blew the 50 amp fuses?

 

[OkiePC]

I noticed this:

Maximum Peak (~ 2 sec) Armature Current: 30A DC
Maximum Continuous Armature Current: 27A DC

Are you perhaps exceeding this limitation?

Also the manual says to use 40A fuses on the line side, and lists some steps for troubleshooting your problem:

1. Line fuses are the wrong size.
2. Motor cable or armature is shorted to ground.
3. Field circuit is open.
4. Nuisance tripping caused by a combination of ambient conditions and high-current spikes (i.e. reversing).

 

[leitmotif]

From somewhere in this mass of confusion I believe it was said only two wires out of motor.

This is either a series or permanent magnet motor.
MOTOR TYPE WOULD SURE BE HANDY TO KNOW.

TEST TO ENSURE MOTOR IS OK - oh yes check to see if you can turn by hand easily.

Now what you should do it take 4 or 6 6 volt batteries hook in series.
1. Start motor on 6 volt record motor terminal voltage and amperage and an idea of speed very slow etc
2. Step up to 12 VDC - same readings
3. 18VDC, then 24 and so on to max voltage you have from batteries.
4. Let motor run for half hour or so until somewhat warm to touch.

If it survives this test then motor should be OK. After that it may be a faulty controller or you have parameters set wrong and doing uncontrolled reverse or other errors.

Rough numbers to expect when you finally get around to taking readings
HP 5
Watts 3730
DC V 180 DC amp 20.7
AC V 240 AC amp15.5

With motor disconnected from load multiply current values by 0.2 - should come fairly close to unloaded current.

As Lancie asked are there any other loads fed from 50 amp fuses?

 

[quebmaint]

I can see it starting right now. 20 questions and pulling hens teeth.

Please supply the following info
1. Line phases and voltage
2. Nameplate on drive or adequate description of rated line voltage and current. Rated motor type volts and amps
3. Nameplate info on motor OR type of motor as I asked for in #3. Include rated voltage and current, HP and RPM. Sure would be nice to include rated torque
4. Take torque wrench and measure torque at the input of the conveyer ideally the gearbox input shaft.

Dan Bentler

1. 240volts single phase
2 minnark drive 240/120 vac 90/180 vdc 5 hp
3 180 vdc 5 hp 1750 rpm 24.5 fla
4 I had the motor unloaded so I wouldn't think torque would be a factor
Thanks again for everyone's involvement

 

[dahnuguy]

Sounds a lot like a wiring to conduit interface.

Could also be moisture.

Second issue could cause first issue.

You could always change the motor and see how the drive responds.

5hp is small enough to hook it up next to the drive to eliminate the wiring and conduit.

or use a megaohm meter to check the wiring.......

no way an unloaded motor that size could pull that much current though, and the motor place said the motor was good, so I have to go with that since I am not there.

All you have is motor, wire / conduit, and drive.

Check each one separately.

A piece of copper pipe will solve the blown 30 amp fuse problem < that's a joke.

 

[quebmaint]

No there is no other loads coming from the 50 amps fuses. I have a powersupply I can hook up I just didn't think it would have enough to run it. It's permanent mag motor. I never really deal with other type dc motors so it really never crossed my mind sorry for the confusion.

 

[quebmaint]

Well the copper pipe would show exactly where the problem is. Lol

 

[Lancie1]

No there is no other loads coming from the 50 amps fuses.

So the situation is that 50 Amp fuses feed 30 amp drive fuses. Drive fuses did not blow, but 50 Amp fuses did. Motor has been tested to be good. Drive appears to work okay. . .

All this says that the problem is not in the motor or drive, but somewhere between the 50-Amp fuses and the drive power terminals.

1. Check the type of 50-Amp fuse being used. Someone may have snuck in a fast-trip type, or a type that is not rated for motor starting. The fuses are supposed to be Bussman SC-40 time-delay current-limiting Class G fuses. Obviously the fuse rating had to be increased from the recommended 40 Amps to 50 to get it to work at all. Using the wrong type (non-time delay) fuse can result in false tripping. Using the wrong fuse can also be unsafe.

2. If the fuses are the correct type, then inspect (with a magnifying glass) the 50-amp fuse holders, the fuse terminal connectors, and the wires from 50-amp fuses to the drive terminals. Check that the drive power terminals are tight, and that there are not hidden wire "whiskers" protruding to cause intermittant shorts. If you have a megohmmeter, disconnect and isolate the wiring section from 50-amp fuses to drive, then test with the megohmmeter.

 

[Lancie1]

A piece of copper pipe will solve the blown 30 amp fuse problem < that's a joke.

The joke may be on you, nuguy, because the 30 amp fuses did not blow! It was the 50 Amp fuses that blew.

 

[OkiePC]

All this says that the problem is not in the motor or drive, but somewhere between the 50-Amp fuses and the drive power terminals.

1. Check the type of 50-Amp fuse being used. Someone may have snuck in a fast-trip type, or a type that is not rated for motor starting. The fuses are supposed to be Bussman SC-40 time-delay current-limiting Class G fuses. Obviously the fuse rating had to be increased from the recommended 40 Amps to 50 to get it to work at all. Using the wrong type (non-time delay) fuse can result in false tripping. Using the wrong fuse can also be unsafe.

2. If the fuses are the correct type, then inspect (with a magnifying glass) the 50-amp fuse holders, the fuse terminal connectors, and the wires from 50-amp fuses to the drive terminals. Check that the drive power terminals are tight, and that there are not hidden wire "whiskers" protruding to cause intermittant shorts. If you have a megohmmeter, disconnect and isolate the wiring section from 50-amp fuses to drive, then test with the megohmmeter.

My guess is fast acting fuses...but the megger check is a good idea too...just don't megger the drive, just the wiring, fuses, and fuse holders.

 

[leitmotif]

Hmm could problem be in the fuses only and why do the 50 blow before the 30.

If the 50 were a quick blow and the 30 a slow blow then this makes sense.

In addition heating of the fuse from poor contact is also a good thing to check - makes some sense because it takes 5 minute to blow the fuse. Also what is ambient temperature around the fuses? Do you have enough cooling?

I dont quite buy that a ground fault will slowly build to the point it blows fuses. Possible I suppose. Megger of insulation quality is always a good thing to do. DISCONNECT all solid state.

Dan Bentler

 

[dahnuguy]

vibration and heat from current can move the conductors in the conduit causing the bare conductor to contact the conduit and ................you know the rest.

I have seen it. Not often though.

Why is the conductor bare? maybe from vibration or scrubbing the conduit from movement. Maybe it was pulled incorrectly or someone recently tried to make the wire longer.

and there is some chance of moisture , maybe even moisture INSIDE the cables. I have seen it.

Oil will sometimes travel through a multi conductor .

I saw a box fill with hydraulic oil once, the source was a valve that leaked and the pressure pushed the oil through the solenoid cable into the box.

So maybe you have some moisture in the conductors?

These are all rare occurrences, but we have exhausted all the common possibilities.

 

[quebmaint]

Well so far I have rewired quite a bit of the system isolating the 240 volt single phase from any of the rest of the controls I'll do some meggering in the morning drive comes Monday hopefully I'll find something that will give me some confidence in starting the new drive. I don't think my company will be to happy if it happens again. I'll keep you posted

 

[Lancie1]

Queb,

Double-check the easy stuff, the things that are so obvious that they are often overlooked. It is easy to have a short-circuit on the terminals of a drive. All it takes are a few stray strands of a stranded cable.

I once saw this where a contractor replaced 3 motor drives, costing the customer $3200 each time, and also required him to install a new ground cable all the way back to the water well, saying the drives were being damaged due to poor grounding. After the 3rd drive faulted on overload, the contractor was told to leave the site. When I was called in, I listened to the sad tale of excuses, went out and opened the motor peckerhead, removed the shorted whiskers from across two terminals, then started it up.