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Module 2
We request you to please complete the Module 0 before taking this up.
Objective of this module
1. You should be able to understand the technology of AC Drives.
2. You should be able to select a suitable drive for any applications.
3. You should be able to program any drive, any make drive, for any application.
4. You should be able to troubleshoot a drive problem.
Q. What is an AC Drive or Variable Frequency Drive (VFD) or ACVVVF Drive (AC Variable Voltage Variable Frequency) or Inverter ?
A. Simple Answer : It converts Input constant AC Supply of Constant Frequency (Say 415 VAC 3 Phase 50 Hz) to Output Variable AC Voltage and Variable Frequency.
Q. Why we need AC Drive ?
A. Simple Answer : To vary the speed of 3 Phase AC Motor ?
Q. Why we need a variable speed of the motor ?
A. Simple Answer : We need to slow down some operation or we need to make faster movement.
Q. How does an AC Drive change the speed of an AC Motor ?
A. Simple Answer : As per AC Motor theory as given in Module 0 the RPM of rotor shaft is 120 * f / p, now obviously we cannot change the number of poles (p) of a motor, so we have to change the frequency (f), and that is what an AC drives. It changes the frequency and thus the RPM of the rotor shaft changes.
Q. Will there be not a problem if frequency is changed ?
A. Simple Answer : Yes, there will be as the torque of the motor depends on frequency, it depends on V/f, that is voltage by frequency ratio, so if we change the frequency keeping the voltage constant then V/f increases, that may cause problem (?) so when we change the frequency we change the V also to make V/f as constant. That is the technology brief of an AC Drive.
Now in practice, we need to connect a drive to a motor and operate the same as per requirement, so we see what are these requirement and how we do it, but before that we have to ensure following..
[How to connect a drive to the motor ?]
1. Refer to the motor specifications, it must be 3 Phase AC Motors.
2. Check the rating of the motor as given in the name plate of the motor, this should be equal to (or may be a size less) the ratings of a drive. For example a 5 HP AC Drive can operate a 5 HP or 3 HP motor, but should not be used for a 7.5 HP Motor.
3. Check the connections of the motor and connect the output terminals (3 Points) directly to the motor. In most of the cases, please do not use anything between drive output terminals and motor terminals...direct connections.
4. Use a suitable size MCB (or MCCB) as explained in the module 0, and connect the power to the drive input terminals. Do not forget to Earth the drive and motor, a terminal will be there on drive as well as on the motor for earthing. Always connect the Earth while using the Industrial Electric goods, otherwise it can be dangerous.
Once you have done it, your basic off line work is over.
[Power on the drive]
Please ensure that..
1. Power connections are made to the right terminals as per drive specifications.
2. Please ensure that motor is of lesser or equal rating then drive.
3. Please ensure that both drives and motors are properly Earthed.
4. Please ensure that suitable rating MCB/MCCB is provided in the input power connections.
It is a healthy practice to measure the voltage on the MCB/MCCB terminals before powering on.
Once all these are ensured please switch on the power to drive. if everything is fine, the display of the drive will come on. If the display does not come on, then there is some problem somewhere.
[How to start a drive]
All the drives can be operated from display, which will have certain keys, in general following operation is required to control the motor.
1. Motor Run in Forward Direction.
2. Motor Run in Reverse Direction.
3. Speed Increase or Decrease.
4. Jogging / Inching
What is Jogging / Inching : This is a simple operation, as long as you press a Jog/Inch button the motor will start with a pre-specified RPM and will stop once the button is released. This operation is generally required to set up the machine.
All these four operations can be carried out from various buttons on the drive. So this way you have started the motor with the drive.
[Now what ?]
[If you want live training with hands on experience, please send a mail to indway1000@gmail.com and we will fix the same for you. On completion of extensive training, a certificate shall be issued to you.]
Module 2
We request you to please complete the Module 0 before taking this up.
Objective of this module
1. You should be able to understand the technology of AC Drives.
2. You should be able to select a suitable drive for any applications.
3. You should be able to program any drive, any make drive, for any application.
4. You should be able to troubleshoot a drive problem.
Q. What is an AC Drive or Variable Frequency Drive (VFD) or ACVVVF Drive (AC Variable Voltage Variable Frequency) or Inverter ?
A. Simple Answer : It converts Input constant AC Supply of Constant Frequency (Say 415 VAC 3 Phase 50 Hz) to Output Variable AC Voltage and Variable Frequency.
Q. Why we need AC Drive ?
A. Simple Answer : To vary the speed of 3 Phase AC Motor ?
Q. Why we need a variable speed of the motor ?
A. Simple Answer : We need to slow down some operation or we need to make faster movement.
Q. How does an AC Drive change the speed of an AC Motor ?
A. Simple Answer : As per AC Motor theory as given in Module 0 the RPM of rotor shaft is 120 * f / p, now obviously we cannot change the number of poles (p) of a motor, so we have to change the frequency (f), and that is what an AC drives. It changes the frequency and thus the RPM of the rotor shaft changes.
Q. Will there be not a problem if frequency is changed ?
A. Simple Answer : Yes, there will be as the torque of the motor depends on frequency, it depends on V/f, that is voltage by frequency ratio, so if we change the frequency keeping the voltage constant then V/f increases, that may cause problem (?) so when we change the frequency we change the V also to make V/f as constant. That is the technology brief of an AC Drive.
Now in practice, we need to connect a drive to a motor and operate the same as per requirement, so we see what are these requirement and how we do it, but before that we have to ensure following..
[How to connect a drive to the motor ?]
1. Refer to the motor specifications, it must be 3 Phase AC Motors.
2. Check the rating of the motor as given in the name plate of the motor, this should be equal to (or may be a size less) the ratings of a drive. For example a 5 HP AC Drive can operate a 5 HP or 3 HP motor, but should not be used for a 7.5 HP Motor.
3. Check the connections of the motor and connect the output terminals (3 Points) directly to the motor. In most of the cases, please do not use anything between drive output terminals and motor terminals...direct connections.
4. Use a suitable size MCB (or MCCB) as explained in the module 0, and connect the power to the drive input terminals. Do not forget to Earth the drive and motor, a terminal will be there on drive as well as on the motor for earthing. Always connect the Earth while using the Industrial Electric goods, otherwise it can be dangerous.
Once you have done it, your basic off line work is over.
[Power on the drive]
Please ensure that..
1. Power connections are made to the right terminals as per drive specifications.
2. Please ensure that motor is of lesser or equal rating then drive.
3. Please ensure that both drives and motors are properly Earthed.
4. Please ensure that suitable rating MCB/MCCB is provided in the input power connections.
It is a healthy practice to measure the voltage on the MCB/MCCB terminals before powering on.
Once all these are ensured please switch on the power to drive. if everything is fine, the display of the drive will come on. If the display does not come on, then there is some problem somewhere.
[How to start a drive]
1. Motor Run in Forward Direction.
2. Motor Run in Reverse Direction.
3. Speed Increase or Decrease.
4. Jogging / Inching
What is Jogging / Inching : This is a simple operation, as long as you press a Jog/Inch button the motor will start with a pre-specified RPM and will stop once the button is released. This operation is generally required to set up the machine.
All these four operations can be carried out from various buttons on the drive. So this way you have started the motor with the drive.
[Now what ?]
[If you want live training with hands on experience, please send a mail to indway1000@gmail.com and we will fix the same for you. On completion of extensive training, a certificate shall be issued to you.]
