LMPForum

Protection System For Dc Drive

Tue, 09 Mar 2010 05:56:10 +0000

Dear Friends,

I have 95KW two old DC drives at our corrugator's single facers. The drives have 6 thyrister protection fuses in series of incoming power. During a problem in machine, fuse are blown which are very costly. I want to install an electronic over current monitoring system. Locally, we have Electronic Over current Relays with CTs for monitoring the AC line current. Is it possible to install that relay for monitoring the incoming 3 phase current?
If not, then what is the recommendation from my friends?

High Load Motor

Sun, 07 Mar 2010 07:31:31 +0000

I need to design a model of 1000 kg lift / elevator. So can u help me with the chosen motor and the data sheet? it can be DC motor @ ac motor.

Running A 50hz 380v Motor On A 60hz 380v Supply

Sat, 06 Mar 2010 21:09:35 +0000

TO ALL MEMBERS,
I HAVE A FAN MOTOR AND THE NAME PLATE INDICATE THE FOLLWING;
DELTA 380V-415V 50HZ
DELTA 460V 60HZ
BUT I ONLY HAVE A GENERATOR THAT IS SET FOR 60HZ 380V
IS SAFE FOR ME TO RUN THIS MOTOR ON THIS SUPPLY VOLTAGE
I REALISE MY V/HZ WILL DROP
i HAVE TESTED THIS MOTOR AND IT DRAWS 27 AMP INSTEAD OF 22.7 AS ON THE NAME PLATE
PLEASE I NEED UR HELP

Short Curcuit Current

Wed, 03 Mar 2010 15:26:14 +0000

Hi guys,

Could you enlighten me on this case?

1. If I calculate the SC current in power system and it showed 17kA.
2. What will happen when I choose the MCCB with SC current rated at 10kA if there is SC in the system?
3. What wil happen when I choose the MCCb with SC current rate at 40kA if there is SC in the system?
4. What exactly is the SC current for the MCCB here?
5. Overcurrent protection will do nothing in this SC case?
6. What exactly the SC current on the MCCb's nameplate means?

Regards,

Problem With Nokian Pf Controller N-12

Wed, 03 Mar 2010 10:53:59 +0000

Dear Friends,

I have Nokian PF controller N-12 in PFI improvement plant in main distribution board which rating is 3500A currently supplying only 500-700A. Capacitors are connected in following sequence;
� Stage 1 & 2 50KVA
� Stage 3 - 6 100KVA
� Stage 7-12 150KVA

System had been working well but this time I have been facing a problem that Nokian PFC switches ON the stages step by step and when PF reaches at 0.95-98, it switches OFF the all stages and PF drops at 0.6-.7. PFC has been continuously repeating that sequence. Can any body help me out?.

Mv Motor Starting

Mon, 22 Feb 2010 18:05:15 +0000

A 13.8KV Motor(2MW) is connected to the main 13.8KV panel thorugh Soft Starter. The main13.8KV panel is on the direct secondary of step down transformer 20MVA 138/13.8Kv, %Z 9.7.
138 KV(primary of trafo) is fed by transmission line (18km long) from a remote generating station of GTG 19MW of a utility grid.
The voltage dip is designed to be not more than 7.5% at 13.8KV bus, by using the soft starter.
Is there any effect anticipated on the Transmsion line on motor starting? if so what precaution shall be taken in design?
What other protection is required?
tramsmmission line is designed to have all normal protection including distance protection

Mv Vfd For Fan

Sat, 20 Feb 2010 18:50:03 +0000

Hi, i am going to select a MV VFD for fan. I am going through all the vendors brochures , however, what are the points i should check thoroughly to avoid VFD failure? also, we are buying motor which will run both on VFD and DOL starting .any special requirement i should check on apart from insulation?
thanks in advance .

Starting Resistor For A 6 Pole Motor

Fri, 19 Feb 2010 14:26:13 +0000

Hi

Can anyone tell me how to calculate the starting resistance of a 6 pole motor
HP=1000/1500
Rotor Volts=740/810
Rotor Amps=301/361
Full speed to reach in 6 stages (6 resistance sections) in one minute
Motor is running against a heavy load (Banbury mixer)
Is there a formula I can use?
Any help is appreciated

Thanks

Slipring Motor Starter

Thu, 18 Feb 2010 00:18:19 +0000

An existing slipring motor with following datas : 650kW, 6kV, 6poles, rotor data 1250V/316A, is started with oil type starter (old fashion starter type, working principle "segment-wise"). The starter datas can not be traced anymore, only some datas are available : 1250V, 316A, ta=30sec, f=1,0, Z=2. If a new motor with follwing datas : 650kW, 6kV, 6poles, rotor data 980V/410A, limited starting current Ia/In <= 2,0, max starting time 30 sec, to be started with the existing oil starter, questions :
1) What is the impact to run the new motor with the existing starter since it has higher rotor current (94A higher) than existing motor?We don't know the maximum current of the short circuit contactor, also the tolerance of the Voltage / current data of the starter, means we don't know the maximum current the starter can deliver.
2) Can the motor be started without problems on the starter itself? E.g oil getting warmer, etc?
3) Or can it be started but with longer starting time?

BR,

GMS

How To Configure The Kw Of Motors

Wed, 17 Feb 2010 05:36:25 +0000

Dear Friends;

We have many motors in our Central Stores without nameplates and we don't know about their ratings. We only know that they are 380V motors. Do anybody have experience how to configure the KW of motor without nameplate?