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Interesting Motor Power Supplies

I think it’s interesting that there are so few switch mode power supplies (SMPS) designed for powering motors.  Motor power requirements are different from electronics; voltage regulation isn’t critical.  Servo motors benefit from a large current peak (overload) capability and sometimes need a shunt.  Steppers are best with a power supply designed to handle a rapidly changing inductive load.

A typical switch mode power supply, however, is designed for tight voltage regulation, does not have a shunt and handles over current by limiting current to its maximum rating.

Some switching power supplies are better because they have 20% to 50% peak capacity for a brief time.  I’ve seen this capability in models from Cabur (sold by ASI in the US), Puls, and Delta; I’m sure there are other examples.

I’ve used the Delta CliQ series for servo motor power, and so far they’ve worked well.  The CliQ can handle 50% over current for 3 seconds, the pricing is quite good (under $150 for 24V at 10A), but they’re only available for 12V and 24V.

The first designed for motors SMPS I discovered was the IMS ISP200/300 series, which are unregulated switching supplies specifically designed for handling the rapidly changing, inductive loads typical of stepper motors or DC motors.  IMS is now Schneider Electric, and they have discontinued the ISP series.

I don’t really consider the Galil PSR series a SMPS for motors; it looks like an ordinary enclosed switcher with an added shunt resistor.  The PSR costs $250, and is available in 24V at 12A or 48V at 6A.

I recently discovered a second SMPS for motors, the Cabur XC series (sold in the US by ASI).  They have a 72-85V output at 3.1A, 6.6A, or 13.3A, have a 20% reserve capacity when <45C, can handle 50% over current for 5 seconds, and have output over-voltage protection (equivalent to a shunt).

It’s interesting to compare the XCSF500G (72V at 6.6A) to the Logosol LS-872.  Logosol makes my favorite linear power supplies (I own a LS-1148 and use it extensively); they are relatively compact, are switch selectable between 115V and 230V input, have ESTOP inputs, front panel mount fuses, and are available in a variety of output voltages.  (The only other 120V/240V switch selectable linear motor power supply I’ve been able to find is Copley’s  DP models in their PST series, but they cost much more).

Cabur XCSF500G Logosol LS-872
Input Voltage 90-132VAC or 187-264VAC 100-120VAC or 200-240VAC (switch selectable)
Output Voltage 72V 72V
Voltage Regulation <1% -10%, +15%
Current, Max Cont 6.7A 8A (50% duty cycle)
Current, Peak 10A for 5 sec 20A for 5 sec
Weight 2.6 lbs 9 lbs
Dimensions Not listed; appears to be smaller than the LS-872 8.55″ x 6.7″ x 2.8″
Other features DIN Rail Mount

Output overvoltage protection

Parallel Connection

Short circuit, overload, and over temp protection

E-Stop Inputs

Separate, unregulated 24V 2.5A power supply

Optional shunt

Approx. Price $550 $425 (no shunt)

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