Regeneration (Back Emf) Effects - Advanced Micro Controls Inc. SMD23E2 User Manual

SMD23E2 and SMD24E2 User's Manual
Power Supply Sizing (continued)
Table R1.4 below shows the suggested power supply sizes based on the maximum power the motor can gen-
erate over its entire speed range.
Motor
Power
24 Vdc
48 Vdc 105 W

Regeneration (Back EMF) Effects

All motors generate electrical energy when the mechanical speed of the rotor is greater than the speed of the
rotating magnetic fields set by the drive. This is known as regeneration, or back EMF. Designers of systems
with a large mass moment of inertia or high deceleration rates must take regeneration effects into account
when selecting power supply components.
The stepper motors used in the SMD23E2 and SMD24E2 units are all low inductance motors. Back EMF is
typically not an issue unless there is a gearhead attached to the motor and it is driven by hand. In these
instances, the motor acts as a generator. With the speed of the motor multiplied by the ratio of the gearhead,
this can lead to large enough voltage spikes to damage the attached power supply.
The first line of defense against regenerative events is an appropriately sized power supply. The additional
capacitance typically found in a larger supplies can be used to absorb the regenerative energy. If your applica-
tion has high deceleration rates, then a supply that can deliver 175% of peak motor power should be used.
The second line of defense is a regeneration resistor, also known as a braking resistor. Braking resistors, and
their control circuitry, are built into AMCI AC powered drives. They are not included in the SMD products
because of the limited ability to dissipate the heat generated by the resistor. An external braking resistor and
control circuitry can be added to the system if needed.
20 Gear Drive, Plymouth Ind. Park, Terryville, CT 06786
Tel: (860) 585-1254 Fax: (860) 584-1973 http://www.amci.com
SMD23E2-130
150% 175%
Supply Supply
53W 80 W 93W
158 W 184 W
Table R1.4 Suggested Power Supply Ratings
SMD23E2 & SMD24E2 S
SMD23E2-240
Motor 150% 175%
Power Supply Supply
57 W 86 W 100 W
135 W 203 W 237 W
PECIFICATIONS
SMD23E2-350
Motor 150% 175%
Power Supply Supply
47 W 71 W 83 W
100 W 150 W 175 W
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