Can I connect two motors in parallel to a single driver?
Currents of two parallel motors add up: the total must stay under 15 A on the KS250 and 30 A on the PT500, and the starting surge must fit the peak window.
You can, but the currents add up. The sum of the two motors' continuous currents under load must not exceed the driver's continuous current rating: 15 A on the KS250, 30 A on the PT500. Because the surge of both motors arrives at the same instant at starting, the total peak also has to fit inside the KS250's 45 A / 5 s or the PT500's 40 A / 15 s window. If these two conditions cannot be met together, the answer is a second driver.
How you do the calculation
- Run each motor on its own, with its real load, and measure its current under load.
- Add the measured values together; that is your continuous current requirement.
- Measure the starting surge, or estimate it, and add the figures for the two together. How many times the rated value the starting current reaches varies with the motor and the load.
- Compare the total continuous current against the driver's continuous rating, and the total surge against the peak rating and its duration. The difference between continuous current and peak current is two separate checks here; clearing one does not mean you have cleared the other.
Using a ramp — the built-in soft start on the KS250, the RMP pot on the PT500 — brings the starting surge down to typically 2-4 times the rated current and noticeably improves the chance of fitting inside the peak window. How long the ramp time should be set depends on the inertia of the load; heavy loads with a high moment of inertia need a longer ramp.
Motors in parallel, or two separate drivers
| Criterion | One driver, motors in parallel | Two separate drivers |
|---|---|---|
| Current budget | The whole current passes through one module | Each module carries its own motor |
| Independent movement | None; both run in the same direction at the same speed | Available |
| End-of-travel detection | The total current is seen, the motors stop together | The end of each motor is detected separately |
| Wiring | One thick common arm | More modules, thinner arms |
Where parallel connection does not fit
Current sensing sees the total current. When one motor reaches its end stop and raises the current, the driver reads that as the movement being over and stops both motors at once; the other motor is left half way. Because AntiSwitch works from a current threshold, this behaviour is not a fault but the natural consequence of the method. If the end points of the motors matter separately, parallel connection is not suitable. The same limit applies to direction and speed: two motors driven from one module cannot run in different directions or at different speeds. Load imbalance makes it harder still; if one motor draws more current than the other, the total reaches the threshold early and the strained motor heats up first.
Wiring and practical checks
Run a separate arm to each motor and choose the cross sections according to their own currents; the common supply arm has to be sized for the total current. Do the cable cross-section selection over the total current and the total distance, not over the value of a single motor. The fuse is chosen according to the total continuous current as well. Before commissioning, run the two motors one at a time and verify that their directions agree; a motor connected the wrong way round strains the mechanism and takes the current to the limit at once.
What to do
Measure the currents separately and add them up, turn the ramp on, and check the total twice — once against the driver's continuous rating and once against its peak rating. If the motors have to stop independently or run at different speeds, plan the second driver from the outset; that is the most expensive decision to correct afterwards.
The full topic: DC Motor Driver Selection Guide