wiad Field Failure Relay - what coil voltage

WILLEO6709 · May 14, 2008

Just tonight the manufacturing EE died - serial 44190 - 12/1959 - Very similar to the square dial project and only 400 serial numbers apart - I thought they were years different instead of months for some reason - main contacvt on the back of the heastock does not latch - traced it the field failure relay not latching B2 and B4 - the diagram on the drive is not very clear on the voltage the coil should be. What does the relay protect? seems like it would not be there without purpose.

rke[pler · May 14, 2008

WILLEO6709 said:
Just tonight the manufacturing EE died - serial 44190 - 12/1959 - Very similar to the square dial project and only 400 serial numbers apart - I thought they were years different instead of months for some reason - main contacvt on the back of the heastock does not latch - traced it the field failure relay not latching B2 and B4 - the diagram on the drive is not very clear on the voltage the coil should be. What does the relay protect? seems like it would not be there without purpose.

The field failure relay will drop out when the field voltage falls below some threshold - something like 15-20 volts. The reason for this is that the DC motor would runaway if the field failed with full armature voltage applied to the motor. Things would get exciting somewhere above 6000-10000 rpm.

I'd check to see if you're generating any field at all, a sudden failure is possibly the 3A fuse(s) on the main tube panel, or perhaps the EL1C rectifier.

WILLEO6709 · May 15, 2008

if you hold the master start contactor closed manually you can get the spindle to run... was just not sure what should be on the coil for the relay, ac or dc. It sounds like DC. I have a relay in a whats left of the drive from my square dial ac conversion project...just its a pain to get to the relay where the turret lathe is sitting. the master start will latch until you try to throw the clutch lever, then unlatches if not held.

rke[pler · May 15, 2008

The parts list description says: "Relay with special coil to carry continuously a maximum current of 1.25 amps and hold in at .35 amps and to drop out the relay at a value below .35 amps. Provided with Normally Open contacts of sufficient capacity to handle the coil current of a size one starter rated 110 volts, open type construction with dead back mounting for not greater than 3/4" mounting plate"

I'd measure the coil resistance on the relay (with one side out of circuit) and I'll do the same here to one or 2 and we'll see if there's something different. If the drive is operating normally either the coil's gone or the contacts.

rimcanyon · May 15, 2008

As Russ said, the problem is more likely the field voltage.

The reason that holding the start button in will keep it running is that the FFR relay is part of the start circuit. If the contacts open due to loss of field, the main contactor opens. Look at the circuit diagram.

The real Leigh · May 15, 2008

rke[pler said:
The parts list description says: "Relay with special coil to carry continuously a maximum current of 1.25 amps and hold in at .35 amps and to drop out the relay at a value below .35 amps. Provided with Normally Open contacts of sufficient capacity to handle the coil current of a size one starter rated 110 volts, open type construction with dead back mounting for not greater than 3/4" mounting plate"

Hi Russ,

Where did you find such a detailed description?

Thanks.

- Leigh

rke[pler · May 15, 2008

The real Leigh said:
Hi Russ,

Where did you find such a detailed description?

Thanks.

- Leigh

It's from the "Master Parts List" from the 1951 WiaD. I don't expect that the FFR changed much in description for this drive.

The real Leigh · May 15, 2008

rke[pler said:
It's from the "Master Parts List" from the 1951 WiaD.

Is that available online?

Thanks.

- Leigh

rke[pler · May 15, 2008

The real Leigh said:
Is that available online?

I could email it to you, I have some relatively high res scans of something like 6 pages. Just send me an email through the profile and I'll have your email address to reply to.

The real Leigh · May 15, 2008

rke[pler said:
Just send me an email through the profile and I'll have your email address to reply to.

Did so.

Thanks very much.

- Leigh

Search

Largest Manufacturing Technology Community on the Web

Search

wiad Field Failure Relay - what coil voltage

WILLEO6709

Diamond

rke[pler

Diamond

WILLEO6709

Diamond

rke[pler

Diamond

rimcanyon

Diamond

The real Leigh

Diamond

rke[pler

Diamond

The real Leigh

Diamond

rke[pler

Diamond

The real Leigh

Diamond

Similar threads