Toshiba G7 Series Applications Workbook page 46

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Encoder Recommendations

Introduction

This guideline is to simplify the selection of encoders that will work with the most common G7

applications while avoiding typical pitfalls.

Shaft encoders for motors may be flange, face or foot mounted. Shaft encoders have no flexture

therefore coupling one to a motor requires a flexible coupling. Direct mount encoders have no shafts

& are mounted directly onto motor shafts. Since coupling between encoder and motor shafts does not

occur, flexible shaft couplings are not required. A hub shaft or hollowshaft encoder should be

mounted so that its shaft receptacle is in as close as possible alignment with the motor shaft. Clamp

or set screws should then be tightened to secure the encoder. Do not defeat or restrict the flexure.

This causes failure of the encoder or driving shaft bearings. A ring kit encoder should be mounted

with its mounting holes in exact alignment with holes or studs on the motor frame. All fasteners

should be equally torqued so as to not distort the ring shape. A gearbox is then positioned on the

motor centered relative to the sensor. The rotation of the motor shaft & gear must be checked to

determine that the specified gap between the gear teeth & sensor is maintained.

All encoders have a power input (+DC), a common & output signal(s). The power input is always

+DC for encoders with a range of 5 to 26 volts & should be regulated to +/-5% at the encoder.

Common should always be connected to the negative (-) side of DC power but not grounded. All

unidirectional encoders will have at least one output signal (A). A bi-directional encoder will have at

least two output signals (A & B). When using bi-directional encoders, the direction of feedback must

match the direction of rotation. Forward rotation is counter clockwise shaft rotation when viewed from

the opposite drive end of the motor (fan end). Reverse rotation is clockwise shaft rotation when

viewed from the opposite drive end of the motor (fan end). An encoder may also include an index

pulse which gives one pulse per revolution. (Z, C, X or index). Do not connect A, B or Z to the + or –

side of DC power.

Forward Rotation

Reverse Rotation

The number of pulses per revolution (PPR) affects the resolution of feedback & thus the accuracy of

the speed regulation. PPR's range from 100 to 2048.

For additional assistance, please contact Toshiba Adjustable Speed Drive Marketing Dept. at (800) 872-2192

H7 series