Faq's Coronet Engineers
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FAQ's

 

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Q 1: What are Costant Torque & Variable Torque applications?

Q 2: What is High Torque & Standard Torque selection?

Q 3: What are the applications on which Energy Saving can be achieved?

Q4 : Can an AC Drive straightaway replace DC Drive?

Q 5 Can AC Drive replace a gear-box?

Q 6 Can an imported m/c designed for 60Hz supply be fed through an AC Drive?

Q 7 Are there any precautions to be taken if output cable length is more?

Q 8 What is RFI / EMI?

Q9 Are Harmonics different than RFI?

Q 10 Can a slip ring induction motor be connected to an AC Drive?

Q 11 What is max safe frequency at which an ordinary motor can be run?

Q 12 While testing a drive with a small motor, why torque is not sufficient at lower speed?

Q 13 What is skip frequency?

Q 14 What precautions are to be taken to operate two or more motors in parallel on one drive?

Q 15 When should auto tuning be used?

Q 16 What is Slip Compensation?

Q 17 What is flying start / catching a spinning load?

Q 18 What is Power loss ride through?

Q 19 What is close loop operation?


Q 1: What are Costant Torque & Variable Torque applications?

A : Application like Conveyors, roller tables, grinder etc. etc. are Constant Torque applications and Centrifugal Pumps & fans are Variable Torque applications.

 

Q 2: What is High Torque & Standard Torque selection?

A : High Torque & Constant Torque are one and the same thing and Standard Torque & Variable Torque are one and the same thing.

 

Q 3: What are the applications on which Energy Saving can be achieved?

A : Energy saving can be achieved on Variable Torque applications.

Q4 : Can an AC Drive straightaway replace DC Drive?

A : No. Starting torque requirement of the load has to be matched with deliverable torque with AC Drive. As a thumb rule one rating higher motor & corrosponding Drive should be proposed.

 

Q 5 Can AC Drive replace a gear-box?

A : No. Gear-box is not only a speed reducer but a torque multiplier as well. (P=NT). For example : If output speed is 1/5th of the input speed, otput torque shall be 5 times the input torque.

 

Q 6 Can an imported m/c designed for 60Hz supply be fed through an AC Drive?

A : Yes only for single motor load. But No for Non-motor loads because output wave shape is a chopped DC and not AC. No for multi motor m/c as well because switching on & off the motor on a operative system with contactors at the output calls for sizing the AC Drive so that it is capable of handling the starting current  (5-6 times) of the incoming motor.

 

Q 7 Are there any precautions to be taken if output cable length is more?

A : Yes, if cable length is more than 100 m, installation of an output choke is strongly recommended. It is advisable to keep the output choke close to motor as for as possible rather than putting it in the drive panel. Pls. Note that output choke sizing  should not be equal to input choke sizing. Refer ATV66 motor choke selection table in 1998 composite catalogue.

 

Q 8 What is RFI / EMI?

A : RFI is Radio Frequency Interference and EMI is Electro Magnetic Interference.

Frequencies in the range of 150 KHz to 20 MHz is called Radio Frequency.

 

Q9 Are Harmonics different than RFI?

A : Yes. Low frequencies of 150 Hz to 10KHz range (in multiples of the base frequency) are called Harmonics.Frequecies ranging from 150KHz to 20MHz are called RFI.

 

Q 10 Can a slip ring induction motor be connected to an AC Drive?

A : Yes. But take care of torque requirement of the load.

 

Q 11 What is max safe frequency at which an ordinary motor can be run?

A : Please check with the motor manufacturer.

Q 12 While testing a drive with a small motor, why torque is not sufficient at lower speed?

A : Auto-tuning can improve the torque performance to some extent. Connecting matching motor shall give excellent performance.

Q 13 What is skip frequency?

A : Every mechanical system has a natural resonance frequency at which a lot of viberation comes into picture. Bypassing that particular frequency (speed) is known as skip frequency. Some systems may have more than one such points.

Q 14 What precautions are to be taken to operate two or more motors in parallel on one drive?

A : a)Drive selection should be such that Nominal output current of drive should be 10- 15% greater than arithmetic sum of nominal currents of motors to be connected in parallel. This is to allow circulating currents.

b) Separate external thermal O/L relay must be incorporated at output for each motor according to their ratings.

Q 15 When should auto tuning be used?

A : Auto tuning can be very helpful in improving torque generated at lower speeds when the motor used is non-standard or does not confirm to IEC standards. Nuisence trippings while using special motors e.g. Textle duty motor can also be avoided by using autotuning.

Q 16 What is Slip Compensation?

A: While working on DOL starter, on-load speed of the motor is lower than no-load speed. For some applications, this speed drop may not be acceptable. This drop can be compensated with the help of Slip compensation parameter.

Q 17 What is flying start / catching a spinning load?

A: Some applications require that drive picks up an already rotating load to desired speed. Flying start / catching a spinning load parameter allows the drive to determine the speed & direction of a rotating motor and begins its ramp output at that speed.

Q 18 What is Power loss ride through?

A : The ability to keep on working while short power interruption is called power loss ride through feature. The duration of Power loss ride through for ATV28 is 300ms and that of ATV58 is 500ms. This an outcome of DC link capacitor power.

Q 19 What is close loop operation?

A : Some applications demand high speed accuracy. Speed accuracy can be improved by using a Pulse Generator or Tacho Generator for actual speed feed back. This is called closed loop operation. ATV58 can accept PG/TG feed back with the help of a suitable I/O Extension card.


 

 






 

 
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