Cutler Hammer Contactors Interrupting Rating & Drop Out Time

Why not do what everyone here will have to do and go the the Cutler Hammer website yourself and get the information.

Then no one will think you are lazy.

Cheers.

Cutler Hammer are most helpful just give them a call. It's simple

Both answers are sensible. i worked for C-H India, knew most of the people at Milwaukee, and i know the company. And i know that they are very helpful.

However, the parameters you are asking are rather strange for contactors. Why do you need them? If you really do need them, you need specialist help.

The figures you give don't seem to match :

10HP ≈ 16A @ 415V 50Hz. 27A?

50HP ≈ 907 A???

Kvsridhar ,

The sopecifcation I chekc from Cutler hammer data sheet .

10 Hp , 27 Amp @ 480V 60 HZ ; 27Amp might me Thermal current ( Ith of contactor ) not rated Amp

Similar for 50HP

Dear Friend ,

I need these as one of our client for which we perform the network coordination study want to check it out that LV circuit breker setting protect the Magnetic contactor from damage . In ETAP software these two addition paramters i.e Interupt capcity in KA and Drop out time is important to check them in TCC curve .

I try Cutler Hammer but so far these details unknonw . I have rated Amp , HP , Hz operating volatge levels etc with me .

Hope for your understanding and appreciate for assit.

Protecting a contactor and overload relay by a circuit breaker is a complex issue. As per IEC 60947-4, two kinds of co-ordination are possible, Type 1 and Type 2. i don't know about US standards. If IEC, which one does your client need? Type 2 is better, but tougher to achieve, especially with a circuit breaker. Such co-ordination tables are published by most manufacturers, since extensive testing is involved.

i hope you are aware that contactors are not meant to interrupt short-circuit currents.

This image may explain better what is Co-ordination...

There are a number of ratings that can be applied to any given contactor.

The thermal current Ith is the maximum continuous current that the contactor can carry.

The rating of the contacts within the contactor is a thermal rating. As the current is increased, the temperature of the contacts increases with the square of the current increase.If there is any overload current, the temperature of the contacts is driven upwards. In many contactor applications, there are regular overloads required. For example, Full voltage starting of induction motors requires an overload current of at least 600% for the duration of the start.In order to keep the maximum temperature of the contacts at acceptable values, the rated current is reduced for applications where such an overload occurs.

Typically, contactors designed for controlling motors, are rated AC3 and are suitable for regular overloads of 600% current every time the motor is started. For arduous starting conditions, use AC4 ratings. - Never use the AC1 (thermal current) for starting motors, but you can use use an AC1 contactor for bypassing a soft starter as it does not carry the starting current. Look at the manufacturers ratings for contactors with the different ratings for AC1, AC3 and AC4.

Here is a picture of a similar Frame 3 Nema Standard Contactor. Kindly look for similarity in the Termal Current within the frame

Please find the attached TCC curve

As seen the Contactor rated Amp is 45A while motor rated amp is 19.6A with Lock rotor 127A. The contactor Interrupt assumed 30K with drop our 20 msec. When perform the coordination of existing C.B 50A, Interrupt rating 100KA HMCP-F Magnetic trip set C (250 A) What do You think it is safer for Magnetic contactor damages during short ckt , or otherwise how we can achieve type 2 coordination for this particular case? Either Increase Contactor rated Amp ( say 100 Amp) and make it beyond the trip curve of CB .

Regards
ASD

i can't see where you get 30kA for the contactor. It is most unlikely, since a 45A contactor is only supposed to make/break 450A a few times in its life.

Anyway, it is immaterial. The MCCB will clear a fault of 30kA or more in less than a quarter cycle, and the contactor may not even have time to react. At the worst, the contacts may part slightly, helping the MCCB in clearing the fault.

However, the manufacturer, in this case Eaton, will give you recommendations of which MCCB, Contactor and Relay to use for Type 2 co-ordination. It is best done by them, not by you, if you don't mind my saying so.

i attach an extract published by ABB.

Kvsridhar ,

Still I am not clear how to solve the matter of contactor rating in ETAP software

The parameters required for contactor in coordination study are attached.

I get the NEMA type contactor Drop out time but interrupting rating still I don't found neither on contactor physically nor from Cutler Hammer and NEMA standard sheet. I assumed the interrupting rating defined in ETAP is the Breaking current of the Contactor. Have you any list that assists for Breaking current of Size 00.... to Size 5 Contactor.

ASD

i have never used ETAP or similar software, so i can't help you with that.

However, i have done many Type 2 coordination studies in India and Europe (ABB and GE), so, for what it is worth, i offer my experiences below :

1. In a motor feeder, for Type 2 cord studies, the fault is assumed to occur at the motor terminals. So, the resistance of the thermal relay which will be in the circuit will attenuate the fault current. A typical 8A relay has a resistance of ≈ 35 mΩ, so a dead-short-circuit will be limited to 240v/0.035 = 6800A. A 40A relay will have ≈ 0.4 mΩ, so the fault will be unlimited by it.

2. The contactor is a zero-current quenching device. ie, the current stops when it passes through its normal zero value on its sine wave. MCCB, on the other hand, is a current-limiting device, ie, it forces the current to zero much before the natural current zero. So, in this combination of MCCB-Contactor-Relay, any "q" current (see post#7) will certainly make the MCCB operate in 6ms or less, and clear the fault. The contractor will not operate at all, so in my opinion, its operating time should not be a parameter in this calculation.

3. In my opinion, the Type 2 co-ordination is a complex one, and no standalone software can do it. ABB does this by testing some combinations, and interpolating/extrapolating other similar ratings. This is because, as the MCCB is opening to clear the fault, the contractor's contacts may open momentarily, aiding the MCCB.

Sorry i missed the fact that what you are looking for is the short-circuit-withstand current for all Eaton contactors. This is not normally provided in catalogues, since it is required for special studies like yours. The techno-commercial department of C-H may be able to give you the values, but i am fairly certain that they will want to know why you need them, then they will tell you about the complexities of Co-ordination, ...so on. Good luck anyway.