What Is a Bore Gauge?
A bore gauge timer is a timer used to start a three-phase AC motor with a bore gauge.
It is sometimes called a star-delta starter. When a motor is started from a complete standstill, a starting current of about 6 to 8 times the rated current is often generated.
This starting current causes instantaneous voltage drops and circuit breaker malfunctions, this can lead to equipment failure. Therefore, industrial equipment often uses star-delta starting to reduce the inrush current.
Star-delta starting is a method in which the motor is first connected with a star connection at motor startup and switched to a delta connection after a certain period. This reduces the starting current. The star-delta timer is a device that assists this switching of wiring.
Uses for Bore Gauges
Bore gauges are mainly used in large industrial equipment. The following are examples of applications for bore gauges:
1. Pumps and Fans
The most common applications for bore gauges are pumps and fans, which typically use high-capacity motors. Star-Delta timers can limit the peak current when these machines start up, thus reducing the load on the motors. Efficient control during startup is especially important for pumps, which are used to move water or liquids.
Examples of large pumps are water supply pumps and pumps for boiler feed water. As for fans, this applies to air blowing fans for industrial burners, etc.
2. Compressors
Compressors are used in air compressors and chillers. These machines often require high current at startup. Star-Delta timers limit the current peak at startup and reduce the load on the power supply.
Bore gauges help compressors run more efficiently and optimize power consumption.
3. Mixers
A mixer is a machine used to mix different ingredients or materials uniformly. Mixers typically use high-capacity motors. Since these motors experience high current peaks when starting, star-delta timers are used to reduce the starting current.
Principle of Bore Gauges
Bore gauges are devices that measure the time required to transition from a star to a delta starting and output a contact signal. Star-delta starting is a starting method in which the wiring method of a 3-phase AC motor is changed in the middle of the motor.
Instead of a slight reduction in starting torque, the starting current is significantly reduced. The switch from star to delta wiring is often controlled by a timer. The system switches to delta wiring after a certain amount of time has elapsed from star wiring. Typical timers start with star wiring for a few seconds to a dozen seconds.
Although it is possible to control star-delta starting using a general-purpose timer, the bore gauge has advantages such as space saving and low power consumption. Some products use plug-in terminal blocks to simplify installation.
How to Select a Bore Gauge
When selecting a bore gauge, the following factors should be considered:
1. Supply Voltage
The bore gauge must be compatible with the power supply voltage to be used. Typically, models are offered on the market that are compatible with major supply voltages, such as 200 VAC. It is important to select a bore gauge with the appropriate supply voltage.
2. Terminal Type
Bore gauges are available with pin-type or plug-in terminals. Pin types include 8-pin and 11-pin products, with 8-pin being the most common. For the pin type, a matching base must be selected.
3. Mounting Method
There are different types of mounting methods, such as surface mounting and embedded mounting. Selection should be made according to the mounting location.
Surface mounting is selected when applied to the inside of a control panel, and most products are DIN-rail mountable. When mounting on the panel surface, ensure to select backside mounting.