fuse blowing on ifc-dps Bridgeport r2e4

[robthomas]

Hi,
Just purchased a R2E4 mill. Applied power to the mill 208 v 3ph it comes up normal but when I enable the drives nothing happens. I have lights on all the drive boards but the fuse supplying the IFC-DPS keeps blowing at power up.
Could this have the wrong size fuse? 1.5 amp. I have no manuals for this machine.

Rob

[JSaindon]

A blown fuse is either wrong size or caused by a short somewhere else. Perhaps a motor or coolant pump shorted out on you. I wish I had manual to check that fuse, but you could test out your motors' coils for a short.

[gar]

071001-1223 EST USA

JSaindon:

Assuming robthomas is not experienced in electrical circuits he needs more than a statement to check for shorts. Where and how does he do this, and what instruments?

Are you talking about shorts to ground, between turns in a winding, or what, and what values? Most likely there is DC power supply. Then there are solid state switches to control the servos.

.

[JSaindon]

I didn't have much info about his problem to work with so I kept it vague, but here is a more indepth explanation.

Before I go into the electrical side of it. Troubleshooting is really just narrowing down your problem to one circuit or area on the machine. Does the machine blow the fuse when you go to power up a servo? Or does it blow the fuse when power is applied for the first time? If it blows when you power the servo then you know where to look to first. Servo hardware and controllers. Test out your motors first since its a fairly quick test. Testing procedure is farther down in the post.

If you are looking at a blown fuse on a PCB, more than likely the problem is limited to just that one board. I can't go into how to troubleshoot shorts on boards since I have no schematic or anything to look at for that particular control. If visible burn marks cannot be seen on the board or its components then your next best bet is to test for continuity to ground throughout the board. If there is a power supply on your IFC&DPS board then that would be the first place I would check for shorts. A good place to start would be any transistors. If a transistor is shorted across every leg it is bad. These are just some "shotgunning" methods I use to rule out the easy checks. Without schematics its hard to tell how the circuit is supposed to operate once it gets passed the power supply. This will be quite difficult and time consuming also.

If you are blowing one of the main fuses then another possibility is a shorted 3 phase motor, whether its a servo or some other motor/pump. Here is a detailed description of what I look for.

FOR 3 PHASE MOTORS
Testing for short to ground using Ohm Meter (10 Mega ohms at least):

Before starting turn off all power sources to machine then disconnect the 3-phase motor lines ONLY from the drive. Check all three wires T1, T2, and T3 individually (all three phases) to the ground wire. Readings should be infinite. If it is zero or reads any continuity at all, then a problem exists with either the motor or cable. If it reads zero, go directly to the motor and disconnect it from the cables and check motor and the cable separately to determine if the problem is in the motor or the cable. Be sure to make sure leads on both ends are not touching anything including the other leads. Most servo motor shorts can be read with a regular quality meter. Make sure you use a quality meter going up to at least 10 megohms.

Testing for Open or short in windings using Ohm Meter:

Disconnect all power from machine. Put meter on ohms. Test with one probe on each of the following:
T1 to T2
T2 to T3
T1 to T3
The safe Ohm range is usually expected to be 0.3 to 2.0 ohms. Most are about .8 ohms. If it reads zero, there is a short between phases and the motor is shot. Usually if it is an open it reads infinite (Usually shows a 1. on the meter) or well above 2K ohms.

Cable and Plug Notes:

Sometimes the connector on the cable to the motor can get coolant in it. Try drying out and retest. If it is still bad the inserts themselves get burn marks in them and cause a slight short and should be replaced. Also look for areas where the cable moves through tracking. Wires will wear through if they aren’t protected from the moving parts.

Maybe that will help some more. Any other info on this problem?

[JSaindon]

If you have a brushed servo (DC). You can try this check.

Measure the resistance between the red and black wire (or whatever color wires the + and - goes to). There should be continuity and some resistance. Turn the servo slowly, the resistance should only vary a little.
Do another resistance test between one of the wires and the motor case, there should be infinite resistance.
You could hook up a DC source equal to the rating on the motor to see if it will spin. Reverse the wires and it will spin the opposite way.