Standstill monitors

Standstill monitor function

Standstill monitors are intended for the reliable control of guard locks. These devices keep isolating protective devices such as safety doors locked until the machines that are posing a hazard have been brought to a standstill. To do this, the standstill monitors measure the induced voltage at the motor supply cable.

The danger points are consequently isolated from the work areas until there is no longer any risk of injury or death posed to personnel. A guard lock release or area release by the standstill monitor is then always required if machines have a long overrun time and continue moving in spite of the motor being switched off, or if external acceleration comes into effect. In contrast to timer relays, which can protect the user against dangerous overrun movements by means of configured time intervals, standstill monitors are more reliable since they monitor the actual motor status.

A differentiation is made between sensorless and sensor-controlled standstill monitors. The sensorless versions are the more economical and convenient solution, as they check for motor standstills without the need for additional motion sensors. As such, time and expense can be saved during commissioning.

The sensor-controlled monitor versions, on the other hand, can be used at the inputs on pulse flow sensors, such as speed sensors, in order to detect standstills.

Where are standstill monitors used?

Standstill monitors are used in case of machines with overrun times. They protect users against the danger posed by machine movements when the motor has already been switched off. For a motor standstill does not always means that the machine has also come to a standstill.

Examples of machines with long overrun times are:

• Sawing machines
• Grinding machines
• Packing machines
• Lathes

Wieland Electric and Schneider Electric standstill monitors are available from stock at Automation24

In the Automation24 online shop, within the Safety technology category, in the Safety drive technology section, you can purchase standstill monitors from the specialists in innovative safety technology Schneider Electric and Wieland Electric.

The standstill monitors from both manufacturers available in the online shop monitor 1 and 3-phase motors without the use of sensors.

Here, the samos® PRO standstill monitors from Wieland Electric are certified for areas of use with a performance level of up to PL e/Cat. 4, in accordance with the ISO13849-1 standard.

The Harmony XPSUVN series from Schneider Electric, on the other hand, is suitable for applications with a performance level of up to PL e/Cat. 3.

All solutions are available with push-in or screw connections.