Connecting P1 and P2 NC Motor Thermostats to Drive

This is rare, someone asking a question and supplying the appropriate manuals which answer the question quite nicely.

Refer page 4 of your motor manual and page 16 of the drive manual (with pictures and an explanation on how to do it too).

I would give you a GA, but the answer's right there, the electrician can take it from there, i'll just take the GA.

the answer is on the 4th page of your manual 3A

I agree with all of what you have said, I'd just like to add that with the motors we used to use Baldor sent us with the P1, P2 thermal wires that are really meant to be wired in a 3 wire hold in circuit. Being we use a DC to AC 3 Phase inverter we don't use them and just cut them off. We have Baldor now supplying our motors with KTY thermistors and these are now wired into our controller to actually perform a controlled cut back if the temp gets to the threshold. For what ever reason Baldor continues to ship us motors with the P1, P2 switch. Go figure. I have been looking for other MFG's. Baldor are not the easiest company to work with on changes. Anyone have some ideas on American Made 3 phase inverter duty motors from 3 - 50 HP in voltages of 36, 48, 72, 96, 108 and 144DC input. Marine environment.

Interesting! Jeaf you are one of the gentlemen here who try to perculate the knowledge without being any lazy!Thank you.

Now please answer my queries & I apologise for being so ignorant.

1.)Why the sreens are earthed at one end only.It is done for preveting the circlating current as being done in single core power cables?Please elaborate.

2)This is what we found finally with resepct to to my thread http://cr4.globalspec.com/thread/99990#newcomments . I understood now that we can wire it so that the drive will log it.

3.)How a non-inveter duty motor get overheated on a drive.

giri,

1. correct. in the USA these are often called "ground loops".

3. I know of two characteristics in the construction of motors that are important for "inverter duty"; JRaef may know others: First, the winding insulation is usually rated for a higher temperature because the motors are frequently run at lower speeds where any external cooling is usually significantly reduced. Second, the winding insulation is designed for the significantly higher voltages that the "carrier frequency" of the inverter's output creates when it reflects off the impedance mismatch between the motor leads and the windings (this reflection in radio terms doubles the voltage at that point).

--JMM

Thank you JMM.I will clarify myself for the point no.3 :)

As they are simply a set/series of dry n/c contacts, you can insert them anywhere in the upstream control circuit (if there is one) that will disconnect the motor when any of them open, paying particular attention to the possibility of auto restarting. Connecting them to the VFD itself may be more problematic as many of them don't provide for this function.

The VFD will likely incorporate its own programmable motor overheat protection which is a function of current and set speed, so the motor ones can be omitted if desired. It will probably also include programming for auto or manual restart on fault clearance.

Many thanks JRaef for the detailed explanation. I am not using the input terminals on the drive for anything else, so I think I will probably get P1 connected to 4 and P2 connected to 13A and set 13A to 21 External Fault.

Just to improve my understanding further (apologies, I don't know much about this). How do you know that it is 24VDC from terminal 4? (on pg 16 of the manual it says that terminal 4 is Digital Reference/Common +15 VDC/0 VDC, depending on assertion level) and also how do you know that this 24 VDC signal is appropriate to go into digital input 13A?

The motor is an inverter duty motor but I will often be running at low speeds. The motor itself didn't come with a manual, but in the cable box it had a picture of the overheat protective device just like on pg 4 of the general manual from the web, so I thought I would put a link to the general manual to show what they say. I was interested in hooking it up through the terminals of the drive so it showed a fault on the drive, but I hadn't been sure how to do it, until you explained it.

Thanks again