Leakage Control Voltage problem is emerging as a challenge for us. A motor is not getting stopped even after pressing emergency push button at field. Motor of 3.7 KW which is for long travel operation of a shuttle conveyor is not getting stopped. Checking results leakage voltage 181V AC in its corresponding power contactor which is enough for contactor pickup of 240V AC rating. Voltage remains after opening connection of 240V common Supply in local push button station. All terminals at this box and its supply panel checked but no abnormality observed. Finally Motor stopped after removing out going control common supply from panel but after few seconds of opening. It indicate that it may be charged voltage in the long run cable but it was not dropping after removing same at field (push button) side. What may be the probable cause and solution ?

 

I don't know what contactor you are using, but I just checked the datasheet for an Eaton DILMP63 (as a quick example of a 240 V contactor) and it lists a sealing power consumption of only 14 VA at 60 Hz. That means that if it is provided with 181 volts, it only needs about 75 mA to remain in the energized state. Once off, it would need about 10x that amount to re-energize.

Having a voltage of 181 volts seems like a usual suspect for getting some induced voltage on an open line (between push button and coil, and it doesn't take a whole lot of current to keep a coil energized. As for solutions unfortunately, I'm not an expert in EMI, so I don't know what the best fix might be...

 

You have to run all control wiring separate from the power feeds. If not, you'll get all sorts of problems.

 

I don't know what contactor you are using, but I just checked the datasheet for an Eaton DILMP63 (as a quick example of a 240 V contactor) and it lists a sealing power consumption of only 14 VA at 60 Hz. That means that if it is provided with 181 volts, it only needs about 75 mA to remain in the energized state. Once off, it would need about 10x that amount to re-energize.

Having a voltage of 181 volts seems like a usual suspect for getting some induced voltage on an open line (between push button and coil, and it doesn't take a whole lot of current to keep a coil energized. As for solutions unfortunately, I'm not an expert in EMI, so I don't know what the best fix might be...

Thank You Mr. David,
FYI we are using L&T MNX 85 3 Pole Power contactor which requires 230V, 50 Hz AC supply.
Yes it seems like an induced voltage or may be a leakage voltage but I don't find a suitable fix.

 

You have to run all control wiring separate from the power feeds. If not, you'll get all sorts of problems.

The control cables are in different cable tray from power. Is there any role of grounding..???

 

The control circuits are usually grounded separately, from the drive power circuits. If not you'll have problems.

 

The control circuits are usually grounded separately, from the drive power circuits. If not you'll have problems.

Sir,
Are you talking about grounding after control transformer...??? Is it required to ground it via a separate earth pit..???

 

That level of question requires electrical drawings. Typically the control circuits are grounded in the control panel separate from grounding in the field.

 

That level of question requires electrical drawings. Typically the control circuits are grounded in the control panel separate from grounding in the field.

Thank U Sir

 

Have run into this induced voltage issue a couple of times. On the emergency stop button you are using you will need to wire a hard common (ground or neutral or opposite polarity if d.c ) on a second n.o. contact on the same switch. Best bet is a contact block with a n.o and n.c built in. One side gets both n.c. and n.o. connected in parallel going to actuated device other side of contact blocks get high voltage on the n.c and on the n.o. side is the neutral or common. This will take all induced voltage to ground. DO NOT USE TWO SEPARATE CONTACT BLOCKS. You could have a race where both blocks are made at the same time. This would cause dead short !!!

 

Also if there is a start button in this circuit you would want a neutral feed when not depressed.
Especially in plc's near high energy fields ( air traffic radio overhead, welding nearby, etc.)