Question:
Is it possible to switch the motor between forward and backward rotations at the contact point of the 1C relay?
Answer:
Do not switch the motor between forward and backward rotations using one relay.
Explanation:
Do not configure a circuit that allows overcurrent to flow or burn out when the contacts are short-circuited.
When switching between forward and backward rotations of the motor with one relay, a short circuit between contacts may occur due to arcing or inrush current at the time of disconnection in a motor with a large load.
In the case of switching between forward and backward rotations of the motor, a potential difference circuit is formed. Use multiple relays and make sure to provide a time lag (off time) between forward and backward rotations.
Inhibited circuit example
- It is a potential difference circuit, and a short circuit is caused by an arc due to a slight opening/closing time difference between the single-polarity contact and the double-polarity contact.
- Depending on the load current of the motor, the large load may cause short circuit due to cutoff and inrush current.
Recommended circuit example
- A switching relay and a power ON/OFF relay are added. The power is switched on after the power of the motor is turned off before switching between forward and backward rotations. One additional relay is required, but short circuit can be avoided.
- The relays for switching between forward and backward rotations are not affected by inrush current and are energized only, thus welding does not occur. For a relay to turn power on and off, select a power relay that takes into account the inrush current of the motor.
Quick tips
The current value of the motor varies depending on the load condition at the time of driving. Select the relay after checking the actual current value.
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