Rockwell Automation Publication 520-UM001K-EN-E - August 2021 219
Appendix E Encoder/Pulse Train Usage and Position StepLogic Application
Wiring Notes The encoder option card can supply 5V or 12V power (250 mA maximum) for an
encoder. Be sure the DIP switch is set properly for the encoder. In general, 12V
will provide higher noise immunity.
The encoder can handle 5V, 12V, or 24V inputs, but the pulse train can handle
only 24V inputs. The inputs will automatically adjust to the voltage applied and
no additional drive adjustment is necessary. If a single-channel input is used,
it must be wired between the A (signal) and A- (signal common) channels.
Determine Encoder Pulse
Per Revolution (PPR)
Specification Based on
Speed Resolution
Use the following formula to determine the encoder pulse per revolution (PPR)
specification based on the speed resolution.
Example 1
To determine the PPR for quadrature encoder, to achieve 0.06 Hz of speed
resolution on a 4-pole motor (2-pole pair) with a base speed of 60 Hz:
Therefore, select 8333 PPR or higher for the quadrature encoder to achieve the
desired speed resolution of 0.06 Hz.
Example 2
To determine the speed resolution, using a 1024 PPR quadrature incremental
encoder on a 4-pole (2-pole pair) motor:
IMPORTANT
A quadrature encoder provides rotor speed and direction. Therefore,
the encoder must be wired such that the forward direction matches the
motor forward direction. If the drive is reading encoder speed but the
position regulator or other encoder function is not working properly,
remove power to the drive, then do one of the following:
• Swap the A and A (NOT) encoder channels.
• Swap the B and B (NOT) encoder channels.
• Swap any two motor leads.
Drives will fault when an encoder is incorrectly wired and A535
[Motor
Fdbk Type] is set to 5 “Quad Check”.
The operating speed range will depend on the motor control mode
selected (SVC or VVC). For more information, see Performance with
Encoder on page 168.
Speed resolution (Hz) =
1
encoder pulse number x 4
10
-3
sec
x pole pairs
0.06 Hz =
= ~8333 pulse
1
encoder pulse number x 4
10
-3
sec
x 2
Speed resolution (Hz) =
1
1024 x 4
10
-3
sec
x 2
= 0.49 Hz
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