When using the operating mode Electronic Gear on Lexium 32 users may find it difficult to understand how to set the gear ratio parameters GEARnum and GEARdenom.
The Lexium 32 offers the possibility to choose from some pre-defined gear ratios with the parameter GEARratio.
Setting of the gear ratio via this means is fairly straight forward and simple.
You choose from one of the pre-defined gear ratios based on the number of pulses per revolution provided from the external reference source.
However, some users may prefer to manual populate a gear ratio, or there may be instances in which the pulses per revolution which are provided by the external reference are not equal to those values which are offered in the pre-defined gear ratio values.
It is in these instances in which setting the gear ratio parameters GEARnum and GEARdenom can be confusing.
It is a common mistake for users to assume the GEARnumerator is equal to motor revolutions.
This is not correct!
The GEARnumerator is equal to internal increments of the Lexium 32.
Again, the GEARnum parameter is directly related to internal increments of Lexium 32.
The internal units per revolution for Lexium 32 is 131072 counts per revolution.
Therefore when populating the gear ratio parameters GEARnum and GEARdenom keep in mind this internal counts per revolution value of 131072.
Example 1:
Assume you have an external encoder that provides 1024 pulses per revolution, and you want the motor that is connected to the Lexium 32 to follow this external encoder at a 1:1 ratio.
You would therefore enter 1024 into the GEARdenom parameter and enter 131072 into the GEARnum parameter.
These settings would mean that for every revolution of the encoder, which is equal to 1024 counts, the motor will move one full revolution, or 131072 increments, which is the internal calculation for one full revolution based on feedback from the motor encoder.
Example 2:
Using the same example encoder from the previous example, lets imagine we want the motor to move at a ratio of twice that of the encoder or 2:1.
Again, we enter 1024 into the GEARdenom parameter (counts per revolution from encoder) but this time enter 262144 into the GEARnum parameter (counts we want from the motor).
These settings would mean that for every revolution of the encoder, which is equal to 1024 counts, the motor will move 262144 increments, or two full revolution, providing a gear ratio of 2:1
Example 3:
Assume we want the motor to move at half the speed or distance of the external encoder.
In this case, we enter 1024 into the GEARdenom parameter (counts per rev from encoder) but this time enter 65536 into the GEARnum parameter (counts we want from the motor).
These settings would mean that for every revolution of the encoder, which is equal to 1024 counts, the motor will move 65536 increments, or 1/2 of a revolution, providing a gear ratio of 1:2
Example 4:
In this example we have two Lexium 32 drives in which drive 1 is the controller drive and drive 2 is following drive 1.
For this configuration you will connect the PTO ( Pulse Train Output ) of drive 1 to the PTI ( Pulse Train Input ) of drive 2 using signal cable VW3M8502R03 or similar.
For the controller drive you only need to configure the parameters of the PTO output to provide it's signal based on the "position actual" of the encoder of drives 1 motor and set the resolution to 4096.
For drive 2, the follower drive, you need to configure the following parameters.
1. Make sure the PTI input is configured for AB type signal.
2. Use the "GEARratio" parameter and set this value to 4096.
3. This example is using position synchronization immediate ( Without Compensation ), which means as soon as the follower drive GearMode is activated the motor on drive 2 will immediately follow the movement of the motor on drive 1.
Care need to be observed if using Postion Synchronization Compensated!
This mode means the follower drive will continue to count the incoming pulses present on the PTI input and buffer the counts internally even when the follower drive is not activated in gearmode. When gearmode is activated the follower drive will attempt to "catch-up to the buffered pulse count and then follow drive 1 This means if there was a large number of pulses present on the PTI input prior to gearmode being activated the follower drive motor can make a very high speed movement in an effort to "catch-up" to the position of drive 1. This can be dangerous if not expected. So be sure to understand and become familiar with Gearmode behavior before use of gearmode with compensation.
There are parameters for gearmode that can be set to limit this "catch-up" speed as well as many other settings for gearmode, this example is only to provide the basics for gearing of two Lexium32 drives.
Summary, the key to remember is that the parameter GEARnum is based on internal counts of the Lexium 32 which are calculated from the feedback of the motor's encoder and that the parameter GEARdenom is the counts that are being provided from the reference source.
The ratio of the Lexium 32 in gearmode when using gear ratio parameters is the relationship between pulses received from the reference source and motor increments which are based on internal calculation of the Lexium 32 which is 131072 increments per revolution.
The Lexium 32 offers the possibility to choose from some pre-defined gear ratios with the parameter GEARratio.
Setting of the gear ratio via this means is fairly straight forward and simple.
You choose from one of the pre-defined gear ratios based on the number of pulses per revolution provided from the external reference source.
However, some users may prefer to manual populate a gear ratio, or there may be instances in which the pulses per revolution which are provided by the external reference are not equal to those values which are offered in the pre-defined gear ratio values.
It is in these instances in which setting the gear ratio parameters GEARnum and GEARdenom can be confusing.
It is a common mistake for users to assume the GEARnumerator is equal to motor revolutions.
This is not correct!
The GEARnumerator is equal to internal increments of the Lexium 32.
Again, the GEARnum parameter is directly related to internal increments of Lexium 32.
The internal units per revolution for Lexium 32 is 131072 counts per revolution.
Therefore when populating the gear ratio parameters GEARnum and GEARdenom keep in mind this internal counts per revolution value of 131072.
Example 1:
Assume you have an external encoder that provides 1024 pulses per revolution, and you want the motor that is connected to the Lexium 32 to follow this external encoder at a 1:1 ratio.
You would therefore enter 1024 into the GEARdenom parameter and enter 131072 into the GEARnum parameter.
These settings would mean that for every revolution of the encoder, which is equal to 1024 counts, the motor will move one full revolution, or 131072 increments, which is the internal calculation for one full revolution based on feedback from the motor encoder.
Example 2:
Using the same example encoder from the previous example, lets imagine we want the motor to move at a ratio of twice that of the encoder or 2:1.
Again, we enter 1024 into the GEARdenom parameter (counts per revolution from encoder) but this time enter 262144 into the GEARnum parameter (counts we want from the motor).
These settings would mean that for every revolution of the encoder, which is equal to 1024 counts, the motor will move 262144 increments, or two full revolution, providing a gear ratio of 2:1
Example 3:
Assume we want the motor to move at half the speed or distance of the external encoder.
In this case, we enter 1024 into the GEARdenom parameter (counts per rev from encoder) but this time enter 65536 into the GEARnum parameter (counts we want from the motor).
These settings would mean that for every revolution of the encoder, which is equal to 1024 counts, the motor will move 65536 increments, or 1/2 of a revolution, providing a gear ratio of 1:2
Example 4:
In this example we have two Lexium 32 drives in which drive 1 is the controller drive and drive 2 is following drive 1.
For this configuration you will connect the PTO ( Pulse Train Output ) of drive 1 to the PTI ( Pulse Train Input ) of drive 2 using signal cable VW3M8502R03 or similar.
For the controller drive you only need to configure the parameters of the PTO output to provide it's signal based on the "position actual" of the encoder of drives 1 motor and set the resolution to 4096.
For drive 2, the follower drive, you need to configure the following parameters.
1. Make sure the PTI input is configured for AB type signal.
2. Use the "GEARratio" parameter and set this value to 4096.
3. This example is using position synchronization immediate ( Without Compensation ), which means as soon as the follower drive GearMode is activated the motor on drive 2 will immediately follow the movement of the motor on drive 1.
Care need to be observed if using Postion Synchronization Compensated!
This mode means the follower drive will continue to count the incoming pulses present on the PTI input and buffer the counts internally even when the follower drive is not activated in gearmode. When gearmode is activated the follower drive will attempt to "catch-up to the buffered pulse count and then follow drive 1 This means if there was a large number of pulses present on the PTI input prior to gearmode being activated the follower drive motor can make a very high speed movement in an effort to "catch-up" to the position of drive 1. This can be dangerous if not expected. So be sure to understand and become familiar with Gearmode behavior before use of gearmode with compensation.
There are parameters for gearmode that can be set to limit this "catch-up" speed as well as many other settings for gearmode, this example is only to provide the basics for gearing of two Lexium32 drives.
Summary, the key to remember is that the parameter GEARnum is based on internal counts of the Lexium 32 which are calculated from the feedback of the motor's encoder and that the parameter GEARdenom is the counts that are being provided from the reference source.
The ratio of the Lexium 32 in gearmode when using gear ratio parameters is the relationship between pulses received from the reference source and motor increments which are based on internal calculation of the Lexium 32 which is 131072 increments per revolution.
Released for:Schneider Electric South Africa
