Help Identifying Relay

[KeepItSimpleStupid]

Nope. Not this time. For a 120 VAC Coil:

https://www.alliedelec.com/schneider-electric-magnecraft-725axxbc3ml-120a/70185406/

or

https://www.alliedelec.com/schneider-electric-magnecraft-725axxsc3ml-120a/70185409/

These guys https://www.onlinecomponents.com/contactuspage.aspx are in NV. They may have it. Hey, the reason why I recommended it was because I have a 12 DC coil version in my possession that I got from onlinecomponents. Mouser.com and Newark.com also carry Magnecraft.

 

[Les Jones]

I was relying on my memory rather than checking the sequence of posts. I thought that Mikes's correction to his typo was referring to to a different post to the one where 14 volts DC was mentioned. Also in my post #37 last night after going to bed I realised I had calculated the resistance of the coil and then said that this was the current. The current should have been 158 mA The resistance is 76 ohms. (KISS The data sheet on your relay actually says 2.5 VA for the AC relay which is not quite the same thing as watts.)

Les.

 

[Les Jones]

Some further thoughts. The fact that Mike could not measure any voltage across the wires that went to the normally open contacts is odd. No matter what the relay is switching I would expect to see the voltage that feeds the item when the contacts are open unless the item had become open circuit. I seem to remember reading the thread that Mike referred back to (But I have not gone back to re read it.) and I think there is mention of the machine using a quartz heater lamp. If that is the case AND if the relay was feeding the lamp it is possible that this has gone open circuit. Although Mike thinks the relay drives the motor I have suspected that may not be the case. There are a few reasons for this. If I have estimated the size of the motor in the picture correctly then I would have guessed it to be about 50 to 100 watts. Also the motor has two sets of brushes so I think one end of the motor is a tacho generator. If this is the case then the motor speed must be controlled by a closed loop speed controller. If all these assumptions are correct then it would be easier to stop and start the motor with a small signal to the speed controller than to use a relay.

Les.

 

[KeepItSimpleStupid]

I know about the VA/Watts thing, but it doesn't belong at the OP's level of understanding.

I think it may go to the lamp too. However, there MAY be another explanation of why no voltage. Interlocks. the lamp going open or shorted for that matter makes more sense. I have seen lamps short. The headlight on one of the cars I owned did, resulting in blinking headlights every 20 seconds or so.

It might be wise to check the resistance of the lamp. HP ratings for a high power lamp makes sense too and not the motor. I have seen and operated one of these things in grade school, but I may have been 10-13 Years old.

FWIW to the OP: Suppose you have a switch(relay), fuse, power and a lamp. The voltage across the switch should be the line voltage when the lamp is off an 0V when the lamp is ON. When you know the circuit configuration, that can be a better test. The voltage ACROSS a switch when the load is on is a good indication of the health of the switch.

ASIDE: If you had the lamp out and measured the voltage across the (not lamp) and got 120 and with the switch off, you got 0. Then when you put the lamp in and got 0 Volts when it's supposed to be on and 0 when its supposed to be off, you could have a bad switch.

 

[Les Jones]

Hi KISS,
That is a valid point about not wanting to confuse the OP more with the distinction between watts and VA. (I was sure from your posts on this and other topics that you would know the distinction.) You make a valid point about interlock switches which I had not considered.

Les.

 

[Les Jones]

Hi KISS and Max,
Just out of interest regarding the significance of the inductance of the coil on the current drawn by an AC relay I decided to do some tests. The nearest to the OP size of relay I could find was one with contacts rated at 15 A at 120 V AC or 10 A at 240 V AC The coil was rated at 180 -264 V (60 HZ)
The coil had a solid core (Not laminated.) with a shading ring on half of the diameter of the core. The measured coil resistance was 3.78 K so if only the resistance was involved in controlling the current the current would be 64 mA With the mains supply at 242 volts (50 HZ) the current drawn with the relay closed was 19 mA. (Total reactance 12740 ohms ) With a piece of plastic inserted between the core and armature to prevent the relay closing the current was 32 mA (Total reactance 7563 ohms ) This shows that the inductance has a significant effect on the current through the coil. This is more than I expected with a solid core. I would expect it to be greater with a laminated core. The measurements were taken using a Fluke 175 meter.

Les.

 

[MaxHeadRoom78]

Did you allow for the fact the actual wire resistance (Ω) appears in series with the inductive reactance (Ω)?
AFA the current calculation is is concerned.
Max.

 

[Les Jones]

Hi Max,
I just measured the current. I did not attempt to measure the inductance as I expect the Q will be very low due to the solid core and the effect of the shorted turn that the shading ring would produce. I did not even attempt to calculate the reactive component (Which I think would be the square root of the total reactance squared minus the square of the resistance.) It was just a test to see how much effect the inductance had on the current. I was thinking that it only had a minimal effect then the faulty relay may have had some shorted turns on the winding. As the inductance had such a significant effect I do not think the faulty relay had any shorted turns. The fact that Mike said that the relay was chattering makes me wonder if there is a fault with whatever drives the relay coil. (For example faulty switch contacts or contacts on a small PCB mounted relay.)

Les.

 

[MaxHeadRoom78]

Inductive reactance can be measured by the current and then subtracting the DC resistance from the total calculated resistance the balance will be the inductive reactance.
Max.