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SMD23E2 and SMD24E2 User’s Manual
SMD23E2 & SMD24E2 SPECIFICATIONS
23
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.
Table R1.4 Suggested Power Supply Ratings
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.
SMD23E2-130 SMD23E2-240 SMD23E2-350
Motor
Power
150%
Supply
175%
Supply
Motor
Power
150%
Supply
175%
Supply
Motor
Power
150%
Supply
175%
Supply
Supply
Voltage
24 Vdc 53W 80 W 93W 57 W 86 W 100 W 47 W 71 W 83 W
48 Vdc 105 W 158 W 184 W 135 W 203 W 237 W 100 W 150 W 175 W
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